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Improvements of Processing Parameters of APIs Raval MK – PhD Thesis 2012

Department of Pharmaceutical Sciences, Saurashtra University, Rajkot 85

4. EXPERIMENTAL

Sr. No.

Topic Page No.

4.1 ANALYSIS OF METFORMIN HCl,

CHLORZOXAZONE AND EXCIPIENTS

89

4.1.1 Materials 89

4.1.1.1 Drugs, excipients and chemicals 89

4.1.1.2 Reagents 92

4.1.1.3 Instruments and equipments 93

4.1.2 Method of analysis 95

4.1.2.1 Introduction 95

4.1.2.2 Experimental 95

4.1.2.2.1 Scanning of Metformin HCl and

Chlorzoxazone by UV

spectrophotometer

95

4.1.2.2.2 Calibration curve of Metformin HCl

and Chlorzoxazone

96

4.1.2.2.3 Scanning of excipients by UV

spectrophotometry

98

4.2 GENERAL METHODS AND EVALUATIONS 100

4.2.1 Co-crystallization 100

4.2.1.1 Methods of preparation of cocrystals 100

4.2.2 Pelletization 102

4.2.2.1 Emulsion solvent diffusion 102

4.2.3 Crystallo-co-agglomeration (CCA) 103

4.2.3.1 Selection of good and poor solvent for drug 103

4.2.3.2 Method of preparation of CCA 103

4.2.4 Cogrinding and amorphization 105

4.2.4.1 Preparation of coground samples 105



4.2.5 Evaluation parameters 106

4.2.5.1 Packability and flow parameters 106

4.2.5.2 Capillary melting point 107

4.2.5.3 Microscopic determination and surface

topography

107

4.2.5.4 Drug loading efficiency and % yield 108

4.2.5.5 Micromeritic study 108

4.2.5.6 Sphericity determination 108

4.2.5.7 Crushing strength 109

4.2.5.8 Heckel plot 109

4.2.5.9 Tensile strength measurement 110

4.2.5.10 Elastic recovery 110

4.2.5.11 Aqueous solubility study 111

4.2.5.12 Differential scanning calorimetry 111

4.2.5.13 Fourier transform infra-red spectroscopy 111

4.2.5.14 Powder x-ray diffractometry 112

4.2.5.15 Scanning electron microscopy 112

4.2.6 Preparation of dosage form and their evaluation 112

4.2.6.1 Preparation of directly compressible tablets of

API and prepared samples

112

4.2.6.2 Evaluation parameters for prepared directly

compressible tablets

113

4.2.6.2.1 Thickness and diameter of tablets 113

4.2.6.2.2 Weight variation test of tablets 113

4.2.6.2.3 Tablet friability test 113

4.2.6.2.4 Tablet hardness test 113

4.2.6.2.5 Tablet disintegration test 113

4.2.7 Dissolution and kinetic study 114

4.2.7.1 In vitro dissolution of prepared samples and

dosage form

114

4.2.7.2 Dissolution parameters 114



4.2.7.3 Statistical analysis of the dissolution profiles 115

4.2.8 Stability study 116

4.3 METHODS USED FOR PROPERTIES

IMPROVEMENT OF APIs

117

1) METFORMIN HCl 117

4.3.1 Preparation of cocrystals of Metformin HCl 117

4.3.2 Evaluation parameters of cocrystals of Metformin

HCl

118

4.3.3 Preparation of dosage form of Metformin HCl and

its evaluation

133

4.3.3.1 Preparation of directly compressible tablets of

Metformin HCl and its cocrystals

133

4.3.4 Dissolution and kinetic study of cocrystals of

Metformin HCl and its dosage form

134

4.3.4.1 In vitro dissolution of prepared cocrystals and

dosage form of Metformin HCl

134

4.3.4.2 Dissolution parameter study of cocrystals and

dosage form of Metformin HCl

136

4.3.4.3 Statistical analysis of the dissolution profiles of

cocrystals and formulation of Metformin HCl

137

4.3.5 Stability study of cocrystals and dosage form of

Metformin HCl

137



2) CHLORZOXAZONE 140

4.3.6 Preparation of pellets of Chlorzoxazone 141

4.3.6.1 32 full factorial design 141

4.3.7 Preparation of CCA of Chlorzoxazone 145

4.3.7.1 Selection of good and poor solvent for

Chlorzoxazone

145

4.3.7.2 Method of preparation of CCA of

Chlorzoxazone

146

4.3.8 Preparation of co-ground samples of

Chlorzoxazone

149

4.3.9 Evaluation parameters of pellets, CCA,

coground samples of Chlorzoxazone

151

4.3.10 Preparation of dosage forms of

Chlorzoxazone and their evaluation

194

4.3.10.1 Preparation of directly compressible

tablets of CCA and coground sample of

Chlorzoxazone

194

4.3.10.2 Evaluation of tablets of Chlorzoxazone 196

4.3.11 Dissolution and kinetic study of pellets, CCA,

coground samples of Chlorzoxazone and its

dosage forms

196

4.3.11.1 In vitro dissolution of pellets, CCA,

coground samples and dosage forms of

Chlorzoxazone

196

4.3.11.2 Dissolution parameters study of pellets,

CCA, coground samples and dosage

forms of Chlorzoxazone

204

4.3.11.3 Statistical analysis of dissolution profiles

of Chlorzoxazone samples and its

formulations

205

4.3.12 Stability study of CCA, coground samples and

dosage forms of Chlorzoxazone

206

4.4 BIBLIOGRAPHY 210



4.1 ANALYSIS OF METFORMIN HCl,

CHLORZOXAZONE AND EXCIPIENTS

4.1.1 MATERIALS

4.1.1.1 Drugs, excipients and chemicals

Table 12: Drugs, chemicals and their source

Sr.

No. Material Source

1 Metformin hydrochloride IP Gifted from Arti drugs Ltd., Mumbai,

India.

2 Chlorzoxazone USP Purchased from Arti drugs Ltd.,

Mumbai, India.

3 Aerosil IP Loba Chemicals, Mumbai, India.

4 Ethyl cellulose Ph Eur Loba Chemicals, Mumbai, India.

5 Eudragit RL100 NF Gifted by Evonik Degussa India Pvt.

Ltd., Mumbai, India.

6 Eudragit RS100 NF Gifted by Evonik Degussa India Pvt.


7 Eudragit S100 NF Gifted by Evonik Degussa India Pvt.


8 Hydroxypropyl

methylcellulose E50 LV IP

S. D. Fine Chem Limited, Mumbai,

India.

9 Kaolin IP Loba Chemicals, Mumbai, India.

10 Klucel EF EP Gifted from Cadila Pharmaceuticals

Pvt. Ltd., Dholka, India.

11 Klucel LF EP Gifted from Cadila Pharmaceuticals

Pvt. Ltd., Dholka, India.

12 Kyron T-314 USP Corel Pharma Chem Pvt. Ltd.,

Ahmedabad, India.



13 Lactose (Anhydrous) Ph Eur Sigma-Aldrich, Mumbai, India.

14 Mannitol IP Himedia Laboratories, Mumbai, India.

15 Magnesium stearate IP Loba Chemicals, Mumbai, India.

16 Microcrystalline cellulose IP Loba Chemicals, Mumbai, India.

17 Neusilin US2 BP Gifted by Gangwal chemicals, Mumbai,

India.

18 Polyethylene glycol 400 NF Merck Pvt. Limited, Mumbai, India.

19 Polyethylene glycol 4000 IP Loba Chemicals, Mumbai, India.

20 Polyvinyl pyrrolidone K30 IP Sisco Research Laboratories Pvt. Ltd.,

Mumbai, India.

21 Purified talc IP S. D. Fine Chem Limited, Mumbai,

India.

22 Sodium chloride IP S. D. Fine Chem Limited, Mumbai,

India.

23 Sodium hydroxide pellets IP Molychem pvt. Ltd., Mumbai, India.

24 Sodium lauryl sulfate IP S. D. Fine Chem Limited, Mumbai,

India.

25 Sodium starch glycolate IP Loba Chemicals, Mumbai, India.

26 Span-80 BP S. D. Fine Chem Limited, Mumbai,

India.

27 Tween – 20 IP S. D. Fine Chem Limited, Mumbai,

India.

28 Acetone AR S. D. Fine Chem Limited, Mumbai,

India.

29 Carbon tetrachloride AR S. D. Fine Chem Limited, Mumbai,

India.



30 Chloroform AR S. D. Fine Chem Limited, Mumbai,

India.

31 Dichloromethane AR Merck Pvt. Limited, Mumbai, India.

32 Ethanol (95%) AR Merck Pvt. Limited, Mumbai, India.

33 Ethyl acetate AR Merck Pvt. Limited, Mumbai, India.

34 Hexane AR Merck Pvt. Limited, Mumbai, India.

35 Light liquid paraffin AR Merck Pvt. Limited, Mumbai. India.

36 Methanol AR Merck Pvt. Limited, Mumbai, India.

37 n-Butanol AR Merck Pvt. Limited, Mumbai, India.

38 N, N-Dimethyl formamide

AR

Merck Pvt. Limited, Mumbai, India.

39 Octanol AR S. D. Fine Chem Limited, Mumbai,

India.

40 Petroleum ether AR Merck Pvt. Limited, Mumbai, India.

41 Propyl alcohol AR Merck Pvt. Limited, Mumbai, India.

42 Toluene AR Loba Chemie Pvt. Limited, Mumbai,

India.



4.1.1.2 Reagents

All the reagents were prepared using double distilled water.

Potassium Chloride (0.2 M) solution: Potassium Chloride (14.911

gm) was transferred in to one liter volumetric flask, dissolved in water

and diluted up to 1000 ml with water.

Hydrochloric acid solution (0.2 M): 7.292 gm of hydrochloric acid

was diluted with 1000 ml water.

Potassium hydrogen phthalate (0.2 M): Potassium hydrogen

phthalate (40.846 gm) was transferred into one liter volumetric flask. It

was dissolved in about 800 ml of water by warming on a water bath

until completely dissolved. The resulting solution was cooled and

sufficient water was added to produce 1000 ml.

Potassium dihydrogen phthalate (0.2 M): Potassium dihydrogen

phthalate (27.218 gm) was transferred into one liter volumetric flask,

dissolved in water and diluted with water to 1000 ml.

Sodium hydroxide solution (0.2 M): Sodium hydroxide pellets (8.0

gm) was transferred in to one liter volumetric flask, dissolved in 200 ml

of water and diluted with water to 1000 ml.

Hydrochloric acid solution (0.1 N): Concentrated hydrochloric acid

(8.5ml) was transferred into one liter volumetric flask, mixed with 200

ml of water and diluted up to the mark with water.

Hydrochloric acid buffer (pH 1.2 buffer): potassium chloride (0.2 M,

250 ml) was transferred in to one liter volumetric flask. Hydrochloric

acid solution (0.2 M, 425 ml) was added and mix. Water was added up

to the mark.

Phthalate buffer (pH 4.6 buffer): Potassium hydrogen phthalate (0.2

M, 250 ml) was transferred in to one liter volumetric flask. Sodium

hydroxide solution (0.2 M, 55.5 ml) was added and mix. Water was

added up to the mark.

Phosphate buffer (pH 6.8 buffer): Potassium dihydrogen phosphate

(0.2 M, 250 ml) was transferred in to one liter volumetric flask. Sodium



hydroxide solution (0.2 M, 112 ml) was added and mix. Water was

added up to the mark.

4.1.1.3 Instruments and equipments

Table 13: Instruments used in experiments

Sr.

No. Instrument Model and Company

1 Automated friability tester

(USP)

EF-2, Electrolab, Mumbai, India.

2 Ball mill Janki Impex Pvt. Ltd., Ahmedabad, India.

3 Charged-coupled device

(CCD) camera

MIPS-USB, Olympus (India) Pvt. Ltd., New

Delhi, India.

4 Constant speed laboratory

stirrer (propeller type)

Remi Motors Ltd., Mumbai, India

5 Cryostatic constant

temperature reciprocating

shaker bath

Tempo Instruments and Equipments Pvt. Ltd.,

Mumbai, India.

6 Differential scanning

calorimeter

DSC-60, TA-60 WS, Shimadzu Corporation,

Japan.

7 Digital hot air oven Nova Instruments Pvt. Ltd., Ahmedabad,

India.

8 Digital melting point

apparatus

Veego instruments Corporation, Mumbai,

India.

9 Digital vernier caliper Mitutoyo, USA

10 Digital weighing balance

(0.1 mg sensitivity)

Shimadzu Corporation, Japan

11 Disintegration tester ED-2L, Electrolab, Mumbai, India.

12 Fourier tranform infrared

spectrophotometer

Nicolet iS10, Thermo Fisher Scientific Inc.,

USA

13 Hardness tester Janki Impex Pvt. Ltd., Ahmedabad, India.



(Monsanto-type)

14 Hydraulic pellet press/KBr

press

Technosearch Instruments, Mumbai, India.

15 Magnetic stirrer with hot

plate

Remi Laboratory Instruments, Mumbai, India.

16 Optical microscope MLX-DX, Olympus (India) Pvt. Ltd., New

Delhi, India.

17 pH-meter Janki Impex Pvt. Ltd., Ahmedabad, India.

18 Powder x-ray

diffractometer

Pan analytical X-ray Diffractometer, Philips,

Mumbai, India.

19 Scanning electron

microscope

JSM-6380LV Scanning Electron Microscope

and JEOL JFC-1600 Auto Fine Coater, JEOL,

UK.

20 Stability chamber Remi Laboratory Instruments, Mumbai, India.

21 Tap density tester (USP) ETD-1020, Electrolab, Mumbai, India.

22 USP dissolution test

apparatus (Type I and II)

TDT 06P, Electrolab, Mumbai, India.

23 UV-visible

spectrophotometer

Pharmaspec - 1700, Shimadzu Corporation,

Japan.



4.1.2 METHOD OF ANALYSIS

4.1.2.1 Introduction

This chapter illustrates development of simple UV spectrophotometric

method for analysis of Metformin HCl and Chlorzoxazone. This chapter also

illustrates the simple UV spectrophotometric analysis of excipients used in the

study in order to confirm their interference in the analysis of drug, if any.

4.1.2.2 Experimental

4.1.2.2.1 Scanning of Metformin HCl and Chlorzoxazone by UV

spectrophotometer(1)

Accurately weighed quantity of drugs (50 mg) was placed in 50 ml

volumetric flask and made up the volume with phosphate buffer pH 6.8. From

the stock solution, 0.5 ml of solution was taken and further diluted to 50 ml to

obtain solution with concentration of 10 μg/ml. This solution was scanned in

UV range from 200 to 400 nm using phosphate buffer pH 6.8 as blank to

determine the λmax of drugs. The UV spectrum is depicted in Figure 3 below.

UV spectrum of Metformin HCl and Chlorzoxazone in phosphate buffer pH 6.8

showed maximum absorbance at 232.5 (233) and 280 nm, respectively.

Figure 3: UV spectrum of Metformin HCl and Chlorzoxazone in

phosphate buffer pH 6.8 solution



4.1.2.2.2 Calibration curve of Metformin HCl and Chlorzoxazone

From the above stock solution (100 µg/ml), appropriate aliquots were

taken into 10 ml volumetric flasks and made up with phosphate buffer pH 6.8

to obtain the desired concentration range (1 to 5 µg ml-1 for Metformin HCl

and 5 to 25 µg ml-1 for Chlorzoxazone). The absorbance of these solutions

was measured at 233 nm for Metformin HCl and 280 nm for Chlorzoxazone

using phosphate buffer pH 6.8 as blank. This procedure was performed in

triplicate to validate the calibration curve. A calibration graph was constructed

by plotting absorbance at selected wavelength versus concentrations of drug

solutions.

The calibration data for Metformin HCl and Chlorzoxazone are given in

Table 14 and 15, respectively. Calibration curve for Metformin HCl and

Chlorzoxazone in phosphate buffer pH 6.8 is shown in Figure 4 and 5,

respectively. The regression equation from calibration curve for Metformin HCl

and Chlorzoxazone was found to be y=0.200x (R2=0.999) and y=0.040x

(R2=0.998), respectively.



Table 14: Data for calibration curve of Metformin HCl in phosphate buffer

pH 6.8 solution

* Each reading is an average of three determinations

0 1 2 3 4 50.0

0.5

1.0 Y=0.200X (R2=0.999)

Conc., g/ml

Ab

s.

Figure 4: Calibration curve of Metformin HCl in phosphate buffer pH 6.8

solution at 233nm

Sr. No. Concentration

(µg/ml)

Absorbance at 233 nm

Abs ± S.D.*

1 0 0.000 ± 0.000

2 1 0.205 ± 0.005

3 2 0.402 ± 0.004

4 3 0.589 ± 0.01

5 4 0.806 ± 0.005

6 5 1.01 ± 0.013



Table 15: Data for calibration curve of Chlorzoxazone in phosphate

buffer pH 6.8 solution

* Each reading is an average of three determinations

0 5 10 15 20 250.0

0.2

0.4

0.6

0.8

1.0Y=0.040X (R

2=0.998)

Conc., g/ml

Ab

s.

Figure 5: Calibration curve of Chlorzoxazone in phosphate buffer pH 6.8

solution at 280 nm

4.1.2.2.3 Scanning of excipients by UV spectrophotometry (2)

A standard stock solution of lactose anhydrous, PVP K30, ethyl

cellulose, HPMC E50LV, PEG 400 and PEG 4000 was prepared separately

by accurately dissolving 25 mg of excipients in 25 ml volumetric flask and

volume was made up with phosphate buffer pH 6.8 solution. From this

standard stock solution, aliquote was pipetted and diluted to 10 ml (10 µg/ml).

UV-scan was taken between the wavelengths of 200- 400 nm using

phosphate buffer pH 6.8 solution as blank. This was carried out in order to

establish compatibility with APIs under consideration.

Sr.

No.

Concentration,

(µg/ml)

Absorbance

± S.D.*

Sr.

No.

Concentration,

(µg/ml)

Absorbance

± S.D.*

1 0 0.000 ± 0.000 4 15 0.295 ± 0.006

2 5 0.075 ± 0.005 5 20 0.402 ± 0.004

3 10 0.205 ± 0.005 6 25 0.496 ± 0.008



Scan of excipients indicated no interference of any excipients with the

max of Metformin HCl and Chlorzoxazone (Figure 6).

Figure 6: UV spectrum of A) lactose anhydrous, B) PVP K30, C) HPMC

E50LV, D) ethyl cellulose, E) PEG 400 and F) PEG 4000 in phosphate

buffer pH 6.8 solution



4.2 GENERAL METHODS AND EVALUATIONS

4.2.1 CO-CRYSTALLIZATION

Pharmaceutical cocrystals made from an active pharmaceutical

ingredient and coformer(s) are solid at ambient conditions. The molecules are

bonded together by interactions which are not covalent or ionic bonds.(3)

Cocrystals results enhancement of physicochemical properties through

modifying the original solid forms.(4, 5) Carbamazepine–saccharin cocrystals

have been one of the best examples for comparison of stability, dissolution

and bioavailability with marketed product. The modification of its melting point,

mechanical properties, stability, solubility and dissolution rate was also

demonstrated.(6-8)

Thus, in the present work, cocrystals of drug have been attempted to

improve their physico-chemical and physico-mechanical properties.

4.2.1.1 Methods of preparation of Cocrystals

Cocrystals can be prepared by solvent and solid based methods. The

solvent-based methods involve slurry conversion, solvent evaporation, cooling

crystallization and precipitation. The solid based methods involve wet

grinding; solvent-assisted grinding and sonication (applied to either to wet or

dry solid mixtures).(9) However, in our experiments, we have utilized solvent

based methods.

Solution co-crystallization

For solution co-crystallization, two components are desired to have similar

solubility; otherwise the least soluble component will precipitate out

exclusively. However similar solubility alone will not guarantee success. The

ability of a molecule to participate in intermolecular interactions obviously

plays a critical role.(10)

Deep freezing: In deep freezing method, co-crystals were prepared in

the presence of coformer(s) by taking the drug: coformer(s) in different ratios



in different solvents as well as combination of different polarity solvents. After

dissolving the drug as well as coformer(s) in the solvent(s) and making the

solution clear, it was filled in a glass bottle having screw cap and kept in a

deep freezer at around 4 to 5 C after proper labeling. Slow agitation was

continued to encourage the crystallization. The nuclei were separated and

acted as seeds for further crystal growth. The time for crystallization was long.

The crystals from the solution were separated and dried at room temperature.

The surface moisture was removed by storing the samples in the desiccators

containing self indicating silica crystals for 1-2 weeks. One batch of optimized

sample of cocrystal was also kept for three months stability study in screw

capped container. The drug was also recrystallized from solvent (control

batch) by maintaining the same above experimental conditions without

dissolving coformer(s) in the solution.

Low Temperature Cooling: Samples were prepared by providing

continuous and slow cooling at 12-15 C to the solutions containing API and

coformer(s) in different ratios with slow agitation. The crystals generated were

separated and dried for overnight at room temperature. The surface moisture

was removed by storing the sample in the desiccators containing self

indicating silica crystals for 1 to 2 weeks.

Solvent evaporation: Samples were prepared by providing continuous

and slow heating to the solutions containing drug and coformer(s) in different

ratios. The crystals obtained were dried for overnight at room temperature.

The surface moisture was removed by storing the sample in the desiccators

containing self indicating silica crystals for 1 to 2 weeks.

Anti-solvent: Good solvents and anti-solvents were identified based

on a random solubility study. A crystallization protocol was developed where

the drug was dissolved in the good solvents and then poured into anti-

solvents which were kept either at room temperature or in cold condition

containing coformer(s) in different ratios with stirring to encourage the



crystallization. Stirring was continued till the crystals started precipitating out.

The generated crystals from the solution were separated and dried at room

temperature. The surface moisture was removed by storing the samples in the

desiccators containing self indicating silica crystals for 1-2 weeks.

Evaporation at room temperature: In room temperature evaporation

(no stress conditions), samples were prepared by keeping the solutions of

drug and coformer(s) combination in different ratios in different solvents at

room temperature for 8-10 days. The crystals from the solution were

separated and dried at room temperature for two days. The surface moisture

was removed by storing the samples in the desiccators containing self

indicating silica crystals for 1 to 2 weeks.

Preparation of drug-coformer physical mixture: The drug-coformer

physical mixture was prepared simply by admixing both in optimized ratio and

stored in desiccator in a screw cap glass bottle.

4.2.2 PELLETIZATION

Pelletization is an agglomeration process that converts fine powders or

granules of bulk drugs and excipients in to small, free flowing, spherical or

semi-spherical units, referred to as pellets.(11, 12) Pellets ensure improved flow

properties and flexibility in formulation development and manufacture.(13)

4.2.2.1 Emulsion solvent diffusion(14, 15)

The pellets were prepared by non-aqueous emulsion solvent diffusion

technique. The excipients (in different ratios) were co-dissolved/dispersed in

internal or external phase (good solvent) and drug was dissolved in internal

phase. The resulting solution was emulsified within the poor solvent and

continuously agitated using mechanical stirrer. The counter-diffusion of the

poor solvent into the droplet induced crystallization of the drug within the

droplet. The prepared pellets were separated by keeping the filter paper on a

sieve and poured the solution containing pellet on it. The collected pellets



were washed three to four times, to remove residual solvent. Finally, pellets

were dried (air dried) for 24 hrs and stored in desiccators. The surface

moisture was removed by storing the samples in desiccators containing self

indicating silica crystals for 1-2 weeks.

4.2.3 CRYSTALLO-CO-AGGLOMERATION (CCA)

Crystallo-co-agglomeration is the particle engineering technique, which

aggregates crystals of drugs in the form of small spherical particles using

excipients and solvents to develop an intermediate material with improved

micromeritic and mechanical properties, solubility and dissolution.(16-19) The

agglomeration is performed using bridging liquid.(20) CCA technique has been

designed to obtain directly compressible agglomerates of low dose, high

dose, single, two, or more drugs in combination with or without diluent drugs

having poor compressibility.(21) The method also enables to formulate

agglomerates containing two drugs or a low dose/poorly compressible drug in

combination with diluent.(16, 17, 22, 23) The rate of dissolution of drug from the

agglomerates or compacts thereof can be improved by using suitable

additives during the process of formation of agglomeration.(18, 24, 25) Moreover,

agglomerates obtained by this technique can be used as directly

compressible tablet intermediates and/or spheres to be encapsulated.

4.2.3.1 Selection of good and poor solvent for drug

It was performed to select good solvent and poor solvent for drug.

Various solvents were selected to cover a range of polarity for this study. 5 ml

of each solvent was taken and the excess amount of drug was dissolved in it.

These saturated solutions were then kept for 24 h in the cryostatic constant

temperature reciprocating shaker bath at room temperature with constant

shaking. The study was repeated for three times in the same manner.

4.2.3.2 Method of preparation of CCA

On the basis of solubility study, good solvent and bad solvent was

identified and selected for the preparation of crystallo-co-agglomerates. A



crystallization protocol was designed in which the drug and/or excipient were

dissolved in good solvent and added drop wise to the bad solvent which was

being stirred by using four blade mechanical stirrers. Here, the good solvent

also acted as a bridging liquid. The stirring was continued for some time. The

stirring was stopped when the overall mixture appeared clear at the top and

the particles settled down. The agglomerates generated were filtered and

dried at room temperature. The surface moisture was removed by storing the

samples in the desiccators containing self indicating silica crystals for 1-2

weeks and stored in a air tight screw cap glass bottle. The CCA of drug were

prepared by maintaining the above experimental conditions without adding

any excipient(s) (control batch) in the solution.

Figure 7: Steps for preparing CCA



4.2.4 CO-GRINDING AND AMORPHIZATION

The bioavailability of poorly solubility drug is often related to the

primary particle size of the drug. For an orally administered drug, to get into

systemic circulation, it must be sufficiently soluble to dissolve in the gastro-

intestinal fluid.(26) The solubility of a compound in the amorphous form is

higher than in the more stable crystalline form because the Gibbs free energy

is higher.(27) The dissolution rate of an amorphous compound is improved

relative to the crystalline form and it can be further improved if the amorphous

compound is dispersed in a hydrophilic polymer. Particle size reduction by

milling without using any organic solvent is one of the approaches for

improving solubility or dissolution rate of poorly water soluble drug.(28)

Amorphization of drug in co-grinding process has been recognized as one of

the most effective way to improve dissolution behavior.(29, 30) The

pharmaceutical processes like grinding can generate defect (disorder) in the

crystal structure and may improve compression characteristics and

dissolution.(31, 32) Grinding approaches have been shown to potentially result

in formation of regions of drug/excipient miscibility.(33) Hydrogen bonding is

widely recognized as an important mechanism to increase amorphous

stability.(34)

4.2.4.1 Preparation of coground samples(35)

A powder mixture comprising of drug and carrier in specific weight ratio

was milled using a ball mill for an extended period of time till dissolution rate

enhanced. The speed of the cylindrical jar was maintained, in a way to allow

significant attrition with some impact. Milling was performed in cold room to

avoid the effect of heat generation. The milled material was sieved through

mesh no. 30 (600 μm opening).

To ascertain the influence of method or carrier or both on the

dissolution rate, drug alone was ground for extended period of time. All

samples were stored in glass vials at room temperature until used for further

analysis. One batch from optimized sample was also kept for three months

stability study in screw capped container.(36, 37)



4.2.5 EVALUATION PARAMETERS

4.2.5.1 Packability and flow parameters

For the rheological characterization of the prepared samples; angle of

repose, carr’s index and hausner’s ratio were measured. Angle of repose was

determined using fixed funnel method.(38, 39) Percentage compressibility (carr’s

Index) and hausner’s ratio were calculated after tapping of fixed amount of

sample using Electrolab tap density tester (USP).(40) Angle of repose () of the

powder material was calculated using formula,

Where, h is height of the pile, and r is radius of the pile(41)

The bulk density (ρb) was the quotient of weight to the volume of the

sample at zero tap. Tapped density (ρt) was determined as the quotient of

weight of the sample to the volume after tapping a measuring cylinder for 500

times from a height of 2 inch. The Carr’s Index (percentage compressibility -

CI) was calculated as one hundred times the ratio of the difference between

tapped density and bulk density to the tapped density.

Hausner’s ratio (HR) was calculated using measured values of bulk density

and tapped density as follows:

Packability parameters like a (compressibility, or amount of

densification due to tapping), 1/b (cohesiveness, or how fast/easily the final

packing state was achieved) and K (Kuno’s constant was determined directly

putting the values of densities) were calculated using Kawakita and Kuno’s

equations at taps 10, 30, 50, 100, 200 and 300.(42-46) The values of ‘a’ and ‘b’

were calculated from the slope and intercept of the linear plot of N/C Vs N,

respectively.



Kawakita equation(47):

Here, where, Y = N/C, Slope = N/a and Intercept = 1/ab, Where,

0

0 )(

V

VVC n

Kuno’s equation:

Where, N is number of tapping

V0 and Vn are initial volume and volume after ‘n’ no. of taps

q0, qn and qt are the initial density, density at ‘n’ taps and density at infinite

taps respectively.

a, b and K are the constants representing flowability and packability of powder

under mechanical force.

The smaller values of parameters ‘a’ and ‘1/b’ in Kawakita equation for

the samples indicated higher packabilities of the sample compared to pure

drug. Higher values of parameter ‘K’ in Kuno’s equation for sample, was an

indication of marked improvement in compressibility and packability attributed

to the much higher rate of their packing processes than that of pure drug due

to sphericity of particles.(47)

4.2.5.2 Capillary melting point

Sample was filled in one end sealed capillary and melting range was

determined on digital melting point apparatus (accuracy ± 0.1 C).

4.2.5.3 Microscopic determination and surface topography

Shape and size of the samples were observed under the optical

microscope with 10X magnification and photomicrographs were taken using

CCD camera for comparing morphological changes in prepared samples



compared to pure drug. The preliminary observation of the shape and surface

of the prepared samples was done and the batches for the further study were

selected.

4.2.5.4 Drug loading efficiency and % yield(48)

Drug loading efficiency is the ratio of experimentally measured drug

content to the theoretical value, expressed as percentage (%).(46)

Accurately weighed quantity of prepared samples were dissolved in

little quantity of a suitable solvent in which it was easily soluble and made the

volume to 50 ml in a volumetric flask. These solutions were appropriately

diluted and drug content was determined by UV spectrophotometer using the

same solvent as blank. The experimental drug content was calculated using

calibration equation. The % yield of sample was calculated using formula

100% polymeranddrugofweighttotal

sampleofweighttotalYield

4.2.5.5 Micromeritic study

Size analysis was performed using optical microscopy method. The

size and size distribution of particles were counted using eye piece

micrometer which was previously calibrated using stage micrometer. Particle

size was determined by taking longest dimension of the particle for a

minimum of 100 particles. Mean aspect ratio (AR), defined as the ratio of

length (longest dimension from edge to edge of a particle oriented parallel to

the ocular scale) to the width (the longest dimension of the particle measured

at right angles of the length) of the particle, was calculated.(49-51) The size of

300 randomly selected particles from prepared batch was measured and

appropriate geometric mean diameter (dg) was calculated.(41)

4.2.5.6 Sphericity determination

Shape factor (SF) and circularity factor (CF) for the prepared sample

were obtained from the area (A) and perimeter (P’) of the particle.(52) The

photomicrographs of the particles were taken at 40X using CCD camera and



tracings of the enlarged photomicrographs were used for the measurement of

area and perimeter.

where P’ = 2π (A/π)½

4.2.5.7 Crushing strength

The crushing strength of the prepared sample was determined by

mercury load cell method using 10 ml hypodermic glass syringe (Figure 8).(53)

The particle was placed inside the syringe and mercury was added through

hollow syringe tube. The total weight of tube with mercury, at the stage where

particle broke, gave the measure of crushing strength of that particle.

Figure 8: Crushing strength measuring device

4.2.5.8 Heckel Plot

Accurately weighed quantity of prepared samples was compressed at

the constant compression at different pressures.(18) The punch and die were

lubricated using 1 % w/v dispersion of magnesium stearate in acetone. The



compression behavior of the samples was expressed as parameters of

Heckel equation.(54) Plot of ln [1/(1-D)] versus P was drawn and values of K, A

and σ0 were obtained.

Where, D is relative density of compacts i.e. ratio of compact density to true

density of powder, P is the applied pressure, K is the slope of Heckel plot; K =

1/Py. Py is the mean yield pressure. The constant A expresses the

densification at low pressure. σ0 is yield strength, σ0 = 1/ 3K.

Here, density of prepared compacts for heckel parameter was

calculated from volume of compacts and mass of compacts.

4.2.5.9 Tensile Strength measurement

After determination of diameter and thickness of compacts prepared for

the study of heckel parameters, the compacts were subjected to relaxation for

24 hours. Then the compacts were subjected to tensile strength measurement

in which the force required to break the compacts (P) was measured using

Monsanto hardness tester.(79) The tensile strength (T, Kg) of the compacts

was calculated using the following equation.(55-58)

LD

PT

0624.0

Where, D and L are the diameter and thickness (cm) of the compacts

respectively. P is force (Kg/cm2) required to break compacts.

4.2.5.10 Elastic recovery

The compacts prepared for the heckel plot study and tensile strength

determination were used for the elastic recovery test. The thickness of the

compacts was measured immediately after ejection (Hc) and after the 24 h

relaxation period (He). Elastic recovery was calculated using the equation.(56)



4.2.5.11 Aqueous solubility study

The solubility was determined in different solvents(59) to correlate

solubility with dissolution and bioavailability. Solubility studies were performed

by adding an excess amount of samples to 10 ml of solvents in specific

gravity bottles until the solutions became saturated at room temperature.

These specific gravity bottles were shaken for 8 h at 25 ± 1 C by keeping in a

cryostatic constant temperature reciprocating shaker bath. The same

procedure was also followed for control batch from solvent without adding any

excipients. The bottles were then opened and solutions were filtered with the

help of whattman filter paper no. 41. The absorbance of the solution was

measured at max of drug by diluting with suitable solvent using same media

as blank.(47) Concentration of drug was calculated by fitting value of

absorbance read in the linear regression equation for the calibration curve of

API at max of drug. All determinations were performed in triplicate.

4.2.5.12 Differential scanning calorimetry(60)

Thermograms of the pure drug and prepared samples were performed

using DSC-60 (Shimadzu, Tokyo, Japan) calorimeter to study the thermal

behavior of drug and prepared samples. The instrument comprised of

calorimeter (DSC 60), flow controller (FCL60), thermal analyzer (TA 60WS)

and operating software (TA 60). The samples were heated in hermetically

sealed aluminum pans under air atmosphere. Empty aluminum pan was used

as a reference.

4.2.5.13 Fourier transform infra-red (FT-IR) spectroscopy(61)

Infrared spectra of pure drug and prepared samples were recorded

using infrared spectrophotometer (FTIR 8400 spectrophotometer, Shimadzu,

Japan). The samples were dispersed in KBr and compressed into disc/pellet

by application of pressure. The pellets were placed in the light path for

recording the IR spectra. The spectrum was recorded.



4.2.5.14 Powder x-ray diffractometry(50, 62, 63)

The x-ray powder diffraction patterns of pure drug and optimized

samples were recorded using PANalytical diffractometer system (Xpert pro

PW 30-40/60) with a copper target and scintillation counter detector (voltage

40 kV; current 30 mA; scanning speed 0.05°/sec). The sample holder was

non-rotating and temperature of acquisition was room temperature. The

diffraction pattern was analyzed in a specific 2 range.(64)

4.2.5.15 Scanning electron microscopy(65)

The shape and surface morphology were observed using scanning

electron microscope (JEOL, JSM 5610 LV). The samples were observed at

various magnifications to have an idea about the effect of various additives on

surface treatment (morphology) and particle size.

4.2.6 PREPARATION OF DOSAGE FORM AND THEIR

EVALUATION

4.2.6.1 Preparation of directly compressible tablets of API and prepared

samples

Formulation excipients were selected on the basis of preliminary tests

which demonstrated no interference of these excipients at the max of API.

Tablets containing equivalent amount of API were made by direct

compression using different formulation excipients of directly compressible

type. Samples used for tableting were having similar size range of particles.

The material for each tablet was weighed (containing equivalent amount of

API), introduced manually into the die and compressed in tablet machine. The

compaction surfaces were lubricated with 2% w/w magnesium stearate in

acetone before compaction. The blend was compressed on an eight-station

rotary tablet machine (Karnawati Engineering Ltd., India) to obtain tablets of

required hardness and thickness. The tablets were studied in three replicates.

The compacts were ejected and stored in screw-capped bottles for 24 h

before using, to allow for possible hardening and elastic recovery. The



compacts were also taken for in-process and finished product evaluation

tests. The same technique was applied for preparation of tablets of API as

well as tablets of control batch.

4.2.6.2 Evaluation parameters for prepared directly compressible tablets

4.2.6.2.1 Thickness and diameter of the tablets

The thickness and diameter of individual tablet was measured with a

vernier caliper, which permitted accurate measurements. The study was

conducted for 20 tablets and average result was considered.

4.2.6.2.2 Weight variation test of the tablets

The USP has provided limits for the average weight of uncoated

compressed tablets. Twenty tablets were weighed individually and the

average weight was calculated.

4.2.6.2.3 Tablet friability test

Tablet friability was measured by using Roche friabilator (Electrolab,

Mumbai). Ten tablets were weighed and placed in the apparatus where they

were exposed to rolling and repeated shocks as they fall 6 inches in each turn

within the apparatus. After four minutes of this treatment or 100 revolutions,

tablets were weighed and compared with the initial weight. The loss due to

abrasion was a measure of the tablet friability.

4.2.6.2.4 Tablet hardness test

Tablet hardness was measured using Pfizer hardness tester. The

instrument measured the force required to break the tablet when force

generated by a coil spring was applied diametrally to the tablet. The test was

done for three tablets from each samples and average was considered.

4.2.6.2.5 Tablet disintegration test

The disintegration test is a measure of the time required under a given

set of conditions for a group of tablets to disintegrate into particles which will



pass through a 10 # screen. The disintegration test was carried out using the

tablet disintegration tester (Electrolab, Mumbai) which consisted of a basket

rack holding 6 plastic tubes, opened at the top and bottom, the bottom of the

tube was covered by a 10 # screen. The basket was immersed in one liter

beaker containing distilled water held at 37 ± 1 oC. As the basket was moved

up and down, tablets kept in the tubes were started disintegrating. The time

required for disintegration of tablet was measured in accordance with the

United States Pharmacopoeia 29.(66)

4.2.7 DISSOLUTION AND KINETIC STUDY

4.2.7.1 In vitro dissolution of prepared samples and dosage form

A USP dissolution test apparatus were used to monitor the dissolution

profiles to evaluate the influence of process and excipients on drug release.

The dissolution medium was equilibrated to 37 ± 0.5 °C. Peddles/ baskets

were rotated at predetermined RPM. From the dissolution flask, 5 ml samples

were withdrawn at selected time intervals(64) and the concentrations of API in

the samples were determined by UV spectrophotometer at max of drug by

diluting with suitable solvent using same media as blank. The mass of API

dissolved was calculated from the concentration after correcting for the

change in volume of the dissolution medium. Concentration of drug was

calculated by fitting value of absorbance read in the linear regression equation

for the calibration curve of drug at its max. All determinations were performed

in triplicate.

4.2.7.2 Dissolution parameters

The dissolution data was analyzed by model independent parameters

calculated at different time intervals, such as dissolution percent (DP),

dissolution efficiency (%DE) and time to release 50% of the drug (t50%). DP

at different time interval and t50% can be obtained from percent dissolution vs

time profile/data.(67)

The concept of dissolution efficiency (%DE) was proposed by Khan

and Rhodes(67) in 1975. Dissolution efficiency is a parameter for the



evaluation of in vitro dissolution data. Dissolution efficiency is defined as the

area under curve (AUC) up to a certain time‘t’ expressed as percentage of the

area of the rectangle described by 100% dissolution in the same time.(68)

100.

%0 100

t

ty

dtyDE

4.2.7.3 Statistical analysis of the dissolution profiles(61)

Model independent mathematical approach proposed by Moore and

Flanner (1996)(69) for calculating a similarity factor ƒ2 was used for comparison

between dissolution profiles of different samples. The similarity factor ƒ2 is a

measure of similarity in the percentage dissolution between two dissolution

curves and is defined by following equation:

1001

1log50

5.0

2

12 ttt

n

t

TRwn

f

Where n is the number of withdrawal points, Rt is the percentage dissolved of

reference at the time point t and T is the percentage dissolved of test at the

time point t. A value of 100% for the similarity factor (f2) suggests that the test

and reference profiles are identical. Values between 50 and 100 indicate that

the dissolution profiles are similar whilst smaller values imply an increase in

dissimilarity between release profiles.

In order to understand difference in dissolution rate of pure drug and

prepared samples, obtained dissolution data were fitted into following

equation. The same calculations were also applied for prepared dosage

forms.

M

MtMDT

n

i

mid

n

i

invitro

1

1

Here, i is dissolution sample number, n is number of dissolution times, t and

tmid is time at the midpoint between times ti and ti-1, and M is the amount of



drug dissolved (mcg) between times ti and ti-1. MDT reflects the time for the

drug to dissolve and is the first statistical moment for the cumulative

dissolution process that provides an accurate drug release rate. It is accurate

expression for drug release rate. A higher MDT value indicates greater drug

retarding ability.

4.2.8 STABILITY STUDY(36, 37)

The optimized batch was placed in 20 ml borosilicate glass ampoule.

The mouth of the ampoule was closed tightly with aluminium foil to prevent

the access of air from the atmosphere to the sample inside the ampoules. Six

such samples were stored at 40 °C and 75% relative humidity (RH) for 3

months. The dissolution behavior of samples and dosage forms was

evaluated in triplicate and characterized.



4.3 METHODS USED FOR PROPERTY IMPROVEMENT

OF APIs

1) METFORMIN HCL

Metformin HCl show very good water solubility (>310 mg/ml), but flow

property and compressibility is a great problem associated in the

manufacturing of solid dosage form for this drug.

Different techniques like pelletization or CCA (as described in section

4.2.2.1 and 4.2.3.2) were tried to improve the flow property of Metformin HCl,

but all the attempts were failed in converting drug as a sphere. The

polymers/excipients either could not bind the drug in a manner to convert a

spherical particle(13, 70, 71) or might not act as a tailor made additive, in order to

change the habit of drug crystals and to control its growth to bind it in a

spherical manner.(72-74)

4.3.1 PREPARATION OF COCRYSTALS OF METFORMIN HCl

Among various solvents used for crystallization of Metformin HCl, only

few solvents like methanol, ethanol and acetone gave encouraging results.

The other solvents such as hexane, chloroform and other low polarity solvents

did not give crystals, might be due to very poor solubility of either drug or

excipients or both. Several studies on the preparation of co-crystals had

included exaggerated stress conditions such as deep freezing, low

temperature cooling, solvent evaporation, anti-solvent, evaporation at room

temperature, etc as described in section 4.2.1.1.(75) Various excipients like

span-20, tween-80, SLS, PEG 400, PVP K30 (PVP), HPC, HPMC E50LV

(HPMC), eudragit RS100 (eudragit), NaCl, lactose anhydrous (lactose),

mannitol, talc, etc were tried as coformer (s) to prepare cocrystals of

Metformin HCl in various concentrations and combinations. The excipients

were co-dissolved in solvents or in combinations of different polarity solvents

in different weight ratios along with Metformin HCl. In all the trials, cocrystals

were developed with poor flow property and hence omitted from the study.

Only lactose gave encouraging result with deep freezing technique to develop



cocrystals of Metformin HCl, where ethanol was used as a solvent and drug:

coformer in various % w/w ratios (0.5 to 3) was applied to generate cocrystals

of desired properties. All other various combinations except drug: lactose

(1:0.5) % w/w imparted very poor flow to cocrystals, hence omitted from the

further study.

In the present study, Metformin HCl: lactose (1:0.5) in % w/w ratio (total

1.5 gm) was dissolved in 25 ml of ethanol at room temperature and stirred to

obtain a clear solution and stored at 4 to 5 C temperature in deep freezer. To

allow adequate amount for subsequent studies including stability, procedure

was then scaled to obtain 30 gm of cocrystals at the same weight ratio in

ethanol at the temperature mentioned above. Time of about 2 to 3 days was

required for obtaining good quantity of crystals. The cocrystals were

separated, dried and stored as described in procedure.

The crystals of Metformin HCl (control batch) were prepared in

absence of lactose anhydrous.

4.3.2 EVALUATION PARAMETERS OF COCRYSTALS OF

METFORMIN HCl

4.3.2.1 Packability and flow parameter study of cocrystals

The packability and flow parameters for Metformin HCl and its

cocrystals were studied as per the procedure described in section 4.2.5.1.

All the combinations of drug: lactose except weight ratio 1:0.5 showed

very poor flow property when measured for angle of repose (29 - 58), carr’s

index (18 - 45) and hausner’s ratio (1.32 - 1.72). Hence, those batches were

omitted from the further study. The result for optimized batch is shown in

Table 16.



Table 16: Flow parameters of cocrystals of Metformin HCl

Sr.

No. Sample

Carr’s Index

S.D.*

Hausner’s

Ratio S.D.*

Angle of

Repose S.D.*

1 Pure Metformin

HCl

38.21 0.56

V. Poor

1.56 1.02

V.V. Poor

45.52 0.55

V. Poor

2 Control batch 40.01 0.34

V.V. Poor

1.67 1.23 V.V.

Poor

58.96 0.12

V. Poor

3 Cocrystals 15.00 0.52

Excellent

1.18 0.88

Good flow

28.07 0.51

Good Flow

*Results are mean ± S.D. of three observations.

Table 16 shows that the flow property of cocrystals was improved

compared to pure drug. It was further confirmed with the study of packability

parameters as shown in Table 17. Here, decreased values of a

(compressibility or extent of densification due to tapping) and 1/b

(cohesiveness, or how fast/easily the final packing state was achieved) than

pure drug in Kawakita equation was an indication of improvement in

packability of cocrystals compared to pure drug. Increased values of K

(Kuno’s constant) compared to pure drug, calculated using Kuno’s equation,

showed marked improvement in compressibility and packability of cocrystals

obtained in presence of lactose.

Table 17: Packability parameters study for pure drug and prepared

cocrystals

Sample Kawakita constant (K)

Kuno’s

constant

a Conclusion b 1/b Conclusion K

Pure

Metformin

HCl

0.429 - 0.139 7.179 - 0.046

Control

batch

0.441 Not

Improved

0.124 8.053 Not

Improved

0.052

Cocrystals 0.202 Improved 0.195 5.135 Improved 0.173



4.3.2.2 Capillary melting point study of cocrystals of Metformin HCl

The melting range of Metformin HCl and prepared cocrystals was

determined as described in section 4.2.5.2.

A clear melting of cocrystals was observed in the range of 180 to 205

C. This range was below the melting point of pure Metformin HCl (242 to 245

C). The melting point of lactose was found in the range of 240 to 245 C. This

reduction in melting point might be due to weak molecular arrangement within

the crystal lattice and low heat of fusion compared to pure drug or

conformer.(76) The distinct melting behavior of crystals indicated formation a

new solid form.(77)

4.3.2.3 Microscopic determination and surface topography of cocrystals

of Metformin HCl

The crystal morphology and influence of excipient on shape of

Metformin HCl, control batch and cocrystals was observed under optical

microscope as described in section 4.2.5.3.

The optical photomicrographs of pure drug (as received), control batch

and cocrystals are shown in Figure 9. The pure drug crystals were irregular in

shape and clubbed together. Control batch crystals were was elongated and

flattened blade shaped (needle like) with sharp edges. The morphology of

cocrystals was more or less equidimensional which was an indication of its

good flow property.(51)

The shape of control batch crystals and pure drug was responsible for

its poor flow property and stickiness due to electrostatic charge generated on

its surface.(40, 50)

The distinct crystal morphology also indicated the formation of a new

solid form (phase).(78)



Figure 9: Photomicrographs of A) Metformin HCl (as received),

B) Metformin HCl crystallized from ethanol, C) Cocrystals

4.3.2.4 Drug loading efficiency and % yield of cocrystals(48)

Accurately weighed 100 mg of cocrystals were dissolved in phosphate

buffer pH 6.8 solution (50 ml). Drug content and % yield were measured as

per the procedure described in section 4.2.5.4 at 233 nm using same pH

solution as a blank.

The percentage yield of cocrystals was 83.33%. The drug content

(loading) in cocrystals was 64.12 ± 0.25 mg Metformin HCl in 100 mg of

cocrystals (96.17%). The results indicated good loading efficiency and %yield.

The rest of the part was made up of lactose anhydrous (35.88 mg).

Hence, the cocrystal stoichiometry was shown to be 1: 0.78 since the

theoretical percentages of the Metformin HCl and lactose anhydrous are

66.67% and 33.33%, respectively.



4.3.2.5 Micromeritic study of Metformin HCl cocrystals

Geometric mean diameter (dg) and aspect ratio (AR) determination for

cocrystals was performed using optical microscopy method as per the

procedure described in section 4.2.5.5.

The geometric mean diameter of prepared cocrystals was 0.78 mm.

The AR was measured for the crystals of control batch (10.39 ± 5.23) and

cocrystals (1.88 ± 0.63). This modified habit of cocrystals with least AR was

an indication of better flow property.(51)

4.3.2.6 Heckel plot study for Metformin HCl cocrystals

Accurately weighed quantity of prepared cocrystals (800 ± 5 mg) was

compressed using 8-mm flat-faced punch at the constant compression at

different pressures ranging from 3 to 9 tons by keeping 1 min. dwell time. (18)

Heckel parameters were calculated as per the procedure described in section

4.2.5.8.

True density was considered as the density of compacts when the

highest pressure applied on the powder (here, 9 tons).(79, 80)

Cocrystals showed remarkable improvement in the packability

compared to pure drug and crystals from control batch (Figure 10). The true

density of cocrystals (2.26 mg/cm3), pure drug (2.17 mg/cm3) and control

batch (2.76 mg/cm3) indicated that, cocrystals were improved in its

compaction properties compared to pure drug (Figure 10).

The constants of heckel plot of pure drug and cocrystals evaluated are

displaced in Table 18.

The slop of heckel plot ‘K’ is an indicative of plastic behavior of the

material. (81) Larger the value of ‘K’, greater is the plasticity in material. The

linearity in the graph (Figure 10) was an indication of plastic deformation.

Table 18 below shows parameters of heckel plot. ‘A’ value of cocrystals was

less than pure drug. This finding suggested that, low compression pressure

was required to obtain closest packing, fracturing its texture and densifying

the fractured particles in case of cocrystals.(82)



0 2 4 6 80

2

4

6

8

Pure Drug

Control batch

Cocrystals

Pressure, ton

ln(1

/1-D

)

Figure 10: Heckel plot of pure drug, control batch and cocrystals

Yield strength (σ0) is an indication of tendency of the materials to

deform either by plastic flow or fragmentation.(83) Low value of yield strength

(σ0) and yield pressure (Py) was again an indication of low resistance to

pressure, good densification and easy compaction.(47)

Thus, heckel plot data suggested that, cocrystals were fractured easily

and new surface of crystals produced might contributed to promote plastic

deformation under applied compression pressure.(81)

Table 18: Heckel plot parameters for cocrystals

Batch Yield

Pressure (Py)

Constant

(A)

Slope

(K)

Yield

Strength (σ0) R2

Pure Drug 7.292 1.1913 0.137 2.433 0.7984

Control batch 2.618 0.7819 0.382 0.873 0.937

Cocrystals 2.11 0.8101 0.474 0.703 0.6665



4.3.2.7 Tensile strength measurement of pellets prepared from

cocrystals of Metformin HCl

The tensile strength of pellets prepared in heckel study was measured

at 9 ton as per the procedure described in section 4.2.5.9.

Tensile strength of cocrystals was increased with pressure, which

indicated improved mechanical properties of cocrystals (Table 19). The

maximum tensile strength was obtained at compression pressure 9 ton. The

high tensile strength of compacts was an indication of strong interparticulate

bonding between the particles.(62)

Figure 11 shows the tensile strength of the compact compressed at

different compaction pressures. Cocrystals possessed superior strength. In

particular, cocrystals compressed into compacts showed considerable

hardness without capping even at high compaction pressure, where as in pure

drug as well as control batch showed lamination after 6 tons.

Table 19: Pressure – tensile strength relationship

Batch Slope R2 Tensile strength at 9 tons

(kg/cm2)

Pure drug 0.532 0.9145 4.83 ± 0.56

(After 6 tons)

Control batch 0.9006 0.9039 7.11 ± 0.67

(After 6 tons)

Cocrystals 1.2503 0.9604 13.53 ± 1.21

(After 9 ton)

*Results are Mean ± S.D. of five observations.

There was an increase in tensile strength of compacts as the pressure

was increased. The relation can be depicted in the following Figure 11.



0 2 4 6 8 100

5

10

15

20

Pure Drug

Drug recrystallized

Cocrystals

Pressure, ton

Ten

sile

Str

en

gth

, K

g/c

m2

Figure 11: Pressure – tensile strength relation

4.3.2.8 Elastic recovery study of pellets of Metformin HCl cocrystals

The elastic recovery of pellets prepared in heckel study was measured

as per the procedure described in section 4.2.5.10.

The result of elastic recovery for cocrystals is given in the following

Table 20. Elastic recovery of cocrystals was very small. At the same time, the

elastic recovery of pure drug and drug recrystallized without excipient was

very high with a behavior of lamination. These findings suggested that

cocrystals were easily fractured, and the new surface of crystals produced

might contributed to promote plastic deformation under compression.(81)

Table 20: Elastic recoveries (ER) of pellets

Pellets prepared from % Elastic recovery ± S.D.*

Pure drug 5.73 ± 0.49

Control batch 4.21 ± 0.22

Cocrystals 1.06 ± 0.38




4.3.2.9 Sphericity determination of Metformin HCl cocrystals

Shape factor (SF) and circularity factor (CF) for control batch and

prepared cocrystals were measured as per the procedure described in section

4.2.5.6.

Shape factor (SF) and circularity factor (CF) of cocrystals were

calculated using area and perimeter of cocrystals and the average was

considered. Area (A) and perimeter (P’) of cocrystals was calculated using

traced photomicrographs. The results revealed in the shape factor (1.2 ± 0.91)

and circularity factor (0.99 ± 0.02), were near to unity (1). Encouraging results

of sphericity determinations indicated the shape obtained of cocrystals was

towards sphericity and it also participated in packing ability of the powder

mass in comparison to the pure drug. (18) Thus, presence of suitable excipient

was required to produce cocrystals with the shape near to spherical and to

provide excellent flow and compaction.(84)

4.3.2.10 Aqueous solubility study of cocrystals

The solubility of cocrystals was determined in different solvents such

as distilled water, 0.1N HCl, pH 1.2 buffer, pH 4.6 buffer and phosphate buffer

pH 6.8 (59) as per the described procedure in section 4.2.5.11. The

absorbance of the solutions was than measured at 233 nm by diluting with

phosphate buffer pH 6.8 using same media as blank.(1) All the determinations

were performed in triplicate.

Solubility data of Metformin HCl and cocrystals are shown in the Table

21 and represented graphically in Figure 12. The solubility of cocrystals was

found to be high in distilled water, pH 4.6 buffer and pH 6.8 buffer solutions,

where as low in 0.1N HCl and pH 1.2 buffer solutions. The recrystallized drug

also behaved in the similar manner. The extent of effect of excipients on

solubility of Metformin HCl was found to be greater in cocrystals over the

solubility of pure drug as well as control batch too.



Table 21: Solubility data of Metformin HCl from pure drug and cocrystals

in different solvents

Solvents

Metformin HCl solubility (mg/ml)

Mean ± S.D.*

% Metformin HCl

solubility

Pure drug Control

batch Cocrystals

Control

batch Cocrystals

Distilled

water

225.12 ±

0.06

339.28 ±

0.12

379.3 ±

0.22 150.71 168.49

0.1 N HCl 184.53 ±

1.05

310 ±

0.61

355.06 ±

1.03 167.99 192.41

pH 1.2

buffer

180.07 ±

0.52

314.31 ±

1.02

351.29 ±

0.02 174.55 195.09

pH 4.6

buffer

217.43 ±

0.01

335.41 ±

0.1

369.8 ±

0.003 154.26 170.08

pH 6.8

buffer

218.21 ±

1.03

338.53 ±

0.17

382.4 ±

0.003 155.14 172.49

* indicates the results are the average of three determinations (n=3)

Figure 12: Solubility of Metformin HCl from pure drug, control batch and

cocrystals in distilled water, 0.1 N HCl and buffer solution of pH 1.2, 4.6

and 6.8 (Mean ± S.D.; n=3)



4.3.2.11 Differential scanning calorimetry (DSC) of Metformin HCl

cocrystals

Thermograms of Metformin HCl, lactose and prepared cocrystals were

recorded as described in section 4.2.5.12.

Figure 13: DSC Thermograms of A) Metformin HCl, B) Co-crystals and C)

Lactose anhydrous

DSC thermograms for Metformin HCl (A), lactose anhydrous (B) and

Metformin HCl-lactose cocrystals (C) are presented in above Figure 13. The

onset values for Metformin HCl-lactose cocrystals and the individual

components agreed with the measured melting points. Metformin HCl showed

a single sharp endothermic melting peak with onset at 244.54 °C (Hf =

324.020 J/gm) (Figure 13-A). Lactose anhydrous demonstrated a steep

endothermic melting transition at 242.72 °C (Hf = 130.924 J/gm) (Figure 13-

B), which is in agreement with reported thermal behavior.(85)

The DSC thermogram for Metformin HCl-lactose anhydrous cocrystals

showed a single endothermic transition attributed to the melting transition

(202.12 °C (Hf = 65.741 J/gm)) (Figure 13-C). The DSC thermographs of

cocrystals showed slight downward shift in the endothermic peak of drug also



indicated the interaction of drug with lactose.(86) It might possible that, drug

and lactose physically behaved like a two phase system.(78)

The thermal behavior of the cocrystal was distinct and unique from the

individual components; this suggests the formation of a new Metformin HCl-

lactose anhydrous cocrystal phase.(87) A single endothermic transition for the

Metformin HCl-lactose anhydrous cocrystals demonstrates the stability of the

phase until the melting point and indicates the absence of any unbound or

absorbed solvent.

4.3.2.12 Fourier transform infra-red (FT-IR) spectroscopy of Metformin

HCl cocrystals (61)

FT-IR spectra of Metformin HCl, lactose and prepared cocrystals were

recorded as described in section 4.2.5.13.

Figure 14: FT-IR Spectra of A) Metformin HCl, B) Lactose anhydrous and

C) Cocrystals



FT-IR spectra of Metformin HCl, lactose anhydrous and cocrystals are

given in Figure 13. The spectrum of Metformin HCl (A) showed characteristic

peaks at 3383.26 cm-1 and 3294 cm-1(-NH2 primary Stretching), 2945.40 cm-1

(-CH3 Stretching), 1630.87 cm-1 (C=N Bending), 1418.69 cm-1 (-NH Bending)

and 1061.85 cm-1 (C-N Bending), respectively. The Spectrum of lactose

anhydrous (B) presented characteristic peaks from 3205.80 cm-1 to 3525.99

cm-1 (Broad, -OH stretching), 2899.11 cm-1 and 1419.66 cm-1 (Strong

stretching of –CH2), 1259.56 cm-1 and 1035.80 cm-1 (Strong Bending of C-O-

C, ether linkage). Broadness of –OH groups depends on no. of hydroxyl

groups and internal H-H boding.

The Spectrum of cocrystals (Figure 14-C) also showed all the

characteristic peaks of drug as well as lactose anhydrous. Furthermore,

broadening of region between 3600 cm-1 to 2800 cm-1 was due to formation of

weak hydrogen bond as well as lower stretching frequencies of primary –NH2

group.(86) This might be due to the weak hydrogen bonding among -NH (NH2

groups of drug) and -OH group of lactose. These findings indicated that,

Metformin HCl and lactose anhydrous did not show interaction by absence of

any additional peak.

4.3.2.13 Powder x-ray diffractometry (pXRD) of cocrystals(50, 62-64)

Powder X-ray diffraction pattern of Metformin HCl and prepared

cocrystals were recorded as described in section 4.2.5.14.

The drug was characterized by distinct 2 values at 28.4156, 22.375,

24.7267, 17.7119, 31.4119, 26.4339, 23.4093 and 37.22 2 (Figure 15). A

shift in peaks was observed in case of crystals generated in presence of

lactose anhydrous. Moreover, as per the XRD spectra, overall peak intensities

are also less in cocrystal spectra compared to pure drug. This was an

indication of decrease in crystallinity.(88) It was assumed that lattice distortions

might had caused deformation of crystals, which had affected peak positions

in powder XRD pattern.(50, 63) Thus, the presence of lactose anhydrous in

crystals might either changed dhkl spacing or loss in periodicity in crystals,

lead to peak shift.(50)



Figure 15: pXRD pattern of A) pure drug and B) crystals generated in

presence of lactose anhydrous

4.3.2.14 Scanning electron microscopy (SEM) of cocrystals

The scanning electron microscopy of Metformin HCl, lactose

anhydrous and cocrystals was performed as per the procedure described in

section 4.2.5.15. It is depicted from Figure 16 that Metformin HCl as well as

lactose anhydrous are crystalline in nature.



Figure 16: Scanning electron microscope of A1 and A2) Metformin HCl,

B1) lactose anhydrous, C1) physical mixture, D1 and D2) drug

recrystallized from ethanol and E1, E2 and E3) cocrystals

The shape of Metformin HCl crystals is small as well as irregular. But

the particles are agglomerated with each other. This aggregation

(cohesiveness) might have become hurdle in its flow.(40)

Crystals from control batch were needle shaped which might again be

a reason of its poor flow property.(89) But the equidimensional crystal habit

may improve the flow as compared to needle shaped crystals. The crystals in

the presence of lactose anhydrous were smaller in size compared to the



recrystallized drug from ethanol. These crystals were near to equidimensional

in shape, which might be the reason in flow property improvement.(65)

Moreover, lactose has tendency to reduce elongation ratio and increase width

of the crystals.(90) The crystals were not cohesive in nature. Thus, the flow

property was improved.

4.3.3 PREPARATION OF DOSAGE FORM OF METFORMIN HCl

AND ITS EVALUATION

4.3.3.1 Preparation of directly compressible tablets of Metformin HCl and

its cocrystals

Tablets containing 250 mg Metformin HCl as well as cocrystals

equivalent to 250 mg Metformin HCl (64.12% drug content in 100 mg of

cocrystals) were prepared by direct compression using different formulation

excipients shown in Table 22. Crystals were ground using a mortar and pestle

to achieve a similar particle size distribution (>250 µm) for each batch and

other formulation excipients were added in it. The material for each tablet was

weighed (250 mg Metformin HCl equivalent), introduced manually into the die

and compressed in tablet machine using 12 mm flat faced punches. The

tablets were prepared and evaluated as per the procedure described in

section 4.2.6.1.

Here, in the preparation of tablets from pure Metformin as well as

control batch, tablets undergone lamination and capping during compaction.

At the same time, tablets prepared from cocrystals, showed no such type of

problem, which was an indication of improvement of compression properties.

Tablets prepared from cocrystals were made similarly but using very

less amount of MCC (Table 22) which was a considerable improvement in the

properties of drug for making directly compressible form. The formulations for

tablet and its evaluations are given in Table 22.

Evaluation of prepared tablets was studied as per the procedure

described in sections from 4.2.6.2.1 to 4.2.6.2.5 and reported in Table 22.



Table 22: Formulation and evaluation of tablets of Metformin HCl

Formulation

and Evaluation

Tablets prepared from

Pure drug Control batch Cocrystals

Metformin HCl, mg 250 250 390 mg

PVP K-30, mg 37.5 37.5 45

Kyron T-314, mg 50 50 60

Magnesium

stearate, mg

5 5 6

Talc, mg 10 10 12

Aerosil, mg 2.25 2.25 3

MCC, mg 145.25 145.25 84

Total wt. of tablet, mg 500 500 600

Hardness*, Kg/cm2 5.7 ± 0.36 6.0 ± 0.51 6.8 ± 0.29

Friability, % 0.17 0.23 0.019

D.T.*, sec. 38.17 ± 5.64 52.5 ± 3.51 193 ± 5.47

Diameter*, mm 12.08 ± 0.007 12.06 ± 0.007 12.09 ± 0.0093

Thickness*, mm 3.89 ± 0.026 3.86 ± 0.047 5.07 ± 0.046

Wt. variation*, mg 506.43 ± 3.93 504.93 ± 4.071 601.81 ± 6.379

* Indicates average of triplicate

4.3.4 DISSOLUTION AND KINETIC STUDY OF METFORMIN

HCL COCRYSTALS AND DOSAGE FORM

4.3.4.1 In vitro dissolution of prepared cocrystals and its dosage form

As per the procedure of dissolution study explained in section 4.2.7.1,

dissolution profiles of pure drug and cocrystals (Type – II) as well as dosage

forms (containing equivalent amount of API) (Type - I) were studied. The

dissolution medium was 900 ml phosphate buffer (pH 6.8) equilibrated to 37 ±

0.5 °C. Peddles /baskets were rotated at 50 RPM. The concentrations of

Metformin HCl in the solutions were determined by UV spectrophotometer at

233 nm by diluting with phosphate buffer pH 6.8 using same media as blank.

All the determinations were performed in triplicate.



Though the drug Metformin HCl is a salt form, dissolution was not a

rate limiting step due to its higher aqueous solubility. All the crystals showed

more than 95% drug release within 20 min (Figure 17). Cocrystals showed

highest rate of dissolution. All the dosage forms also showed very rich

dissolution profiles. In all the cases, drug release was more than 90% within

one hour (Figure 17).

Table 23: Data of dissolution profiles of cocrystals (Powder)

Powder dissolution from (CPR ± S.D.*)

Time (min.) Pure drug Control batch Cocrystals

0 0.00 ± 0.00 0.00 ± 0.00 0.00 ± 0.00

5 91.69 ± 2.33 88.26 ± 2.68 98.44 ± 0.67

10 94.77 ± 2.21 94.59 ± 0.96 97.84 ± 1.32

15 98.45 ± 1.37 98.70 ± 0.47 99.27 ± 2.02

20 100.10 ± 0.75 100.00 ± 0.80 100.70 ± 0.43

* Indicates the results are the average of three determinations (n=3)

Table 24 below shows drug release from dosage form prepared from

pure drug and cocrystals.

Table 24: Data of dissolution profiles of cocrystals (Tablets)

Tablet dissolution from (CPR ± S.D.*)

Time (min) Pure drug Control batch Cocrystals

0 0.00 ± 0.00 0.00 ± 0.00 0.00 ± 0.00

5 75.58 ± 1.15 72.26 ± 3.58 72.5 ± 2.17

10 90.4 ± 1.95 88.21 ± 1.43 97.93 ± 0.51

15 93.38 ± 2.16 88.21 ± 0.87 95.11 ± 1.53

20 98.05 ± 0.59 88.91 ± 4.17 95.26 ± 1.16

30 101.6 ± 2.38 89.66 ± 4.64 94.15 ± 2.41

40 100.7 ± 1.22 92.3 ± 5.42 94.75 ± 1.05

50 101 ± 1.34 93.97 ± 3.45 94.6 ± 0.79

60 99.88 ± 0.8 96.9 ± 5.47 94.88 ± 3.44

* Indicates the results are the average of three determinations (n=3)



Figure 17: Powder and dosage form dissolution profile of pure drug,

control batch and cocrystals

4.3.4.2 Dissolution parameter study of cocrystals and dosage form of

Metformin HCl

Dissolution parameters such as dissolution percent (DP5 min),

dissolution efficiency (%DE10) and time to release 50% of the drug (t50%)

were calculated by taking pH 6.8 (phosphate buffer) using equations

described in section 4.2.7.2.

Table 25: Value of %DE10, DP5 min and t50 for powder as well as formulation

%DE10 DP5 min, % t50, min

Sample P T P T P T

Pure Drug 70.82 64.45 98.75 76.2 2.4 3.25

Cocrystal 68.72 65.55 88.75 78.7 2.5 3.25

Control batch 67.47 63.45 88.75 75 2.6 3.40

P – Powder dissolution, T – Tablet dissolution

The above results showed that, there was a negligible difference in the

dissolution parameters of pure drug and cocrystals as the drug was highly

water soluble.



4.3.4.3 Statistical analysis of the dissolution profiles of cocrystals and

formulation of Metformin HCl(61)

Similarity factor (f2) and mean dissolution time (MDT) were calculated

for the comparison of dissolution profiles of cocrystals with pure Metformin

HCl and control batch studied in pH 6.8 (phosphate buffer) as per the

equations mentioned in section 4.2.7.3.

The values are shown in Table 26. From the results of Table 26, it was

seen that there was similarity (f2 > 50) in dissolution profiles of cocrystals with

pure drug or drug recrystallized. Though, the drug was freely soluble in

aqueous media, dissolution rate was also very high. All the results of

dissolution parameters also showed similar results.

Table 26: Value of f2 and MDT for powder as well as formulation

f2 MDT, min.

Sample P T P T

Pure Drug -- -- 4.13 6.57

Cocrystal 81.2* 67.2* 5.16 9.39

Control batch 74.4* 68.2* 3.57 6.82

* Similarity between dissolution profiles

MDT showed higher results for formulation in all the samples. It was so

because the powder was compressed in tablet form which took some time for

drug release from the formulation.(91)

4.3.5 STABILITY STUDY OF COCRYSTALS AND DOSAGE

FORM OF METFORMIN HCl

Stability study of prepared cocrystals was done as per the procedure

described in section 4.2.8.

The amount of Metformin HCl in the cocrystals was found 63.47 ± 0.13

mg after the storage. The reduction in drug content was very negligible

(1.02%). The dissolution profile of stored of cocrystals (Figure 18) was also



similar compared to cocrystals soon after the preparation. The statistical

analysis also proved sameness in dissolution profile (f2=94.86).

The dissolution profile (Figure 18) of prepared dosage form in case of

cocrystals was similar to that of the dosage form prepared immediately. The

statistical analysis of dosage form dissolution profile of cocrystals after

stability study also proved sameness (f2=89.35) with their respective dosage

form before stability study.

Figure 18: Dissolution profiles of cocrystals and dosage form before and

after stability testing FTIR analysis

Figure 19: FT-IR study for A) Cocrystals before stability study, B)

Cocrystals after stability study



The FT-IR analysis (Figure 19) showed no change in the peak

positions, which confirmed the stable nature of cocrystals. Thus, the

cocrystals of Metformin HCl: lactose anhydrous (1:0.5) weight ratio was found

to be stable.

DSC spectra

Figure 20: DSC study for A) Cocrystals before stability study,

B) Cocrystals after stability study

From the above figure, the DSC spectra of cocrystals, which was kept

for stability study for 3 months at 40 °C showed no extra endothermic peak

appearance or disappearance. Thus, the DSC spectra confirmed that no

physical and chemical interaction occurred and the cocrystals of drug were

found to be stable.



2) CHLORZOXAZONE

Chlorzoxazone showed poor water solubility, poor flow property and

problems of compressibility in the manufacturing of solid dosage form.

Various techniques of conventional cocrystallization as described in section

4.2.1.1 were adopted using solvent system as alone or in combination with

wide range of polarity in presence of excipient(s). Among various solvents

used for crystallization of drug, only few solvents like methanol, ethanol and

acetone gave encouraging results. The solvents such as hexane, chloroform

and other low polarity solvents did not yield crystals, might be due to very

poor solubility of either drug or excipients or both. Various excipients like

span-20, tween-80, SLS, PEG 400, PVP K30 (PVP), HPC, ethyl cellulose,

HPMC 50LV (HPMC), eudragit RS100 (eudragit), NaCl, lactose anhydrous

(lactose), mannitol, talc, etc were tried, but all resulted in poor yield and poor

flow properties with needle shaped cocrystals.

The probable reason was blocking of some faces by polymers in order

to cease its growth and produced elongated crystals.(73) Moreover, if the

solvent was strongly bonded to drug at specific crystal face by interacting with

specific functional groups, crystal growth was rate limited by the removal of

solvent from that face. As a result, the bonded surface grew slowly leading to

a more elongated crystal.(92) Here, crystallizing solvent might had higher

affinity for the functional groups of Chlorzoxazone and resulted in elongated

crystals.(93) As the supersaturation increased, the rate of nuclei formation was

greater than crystal growth and growth occurred mainly in one direction by

producing elongated crystals.(89)

Cocrystals of Chlorzoxazone: tween-80 (2:1% w/w) by deep freezing

technique and Chlorzoxazone: lactose anhydrous (2:1% w/w) by solvent

evaporation using ethanol as a solvent in both the cases, showed higher

solubility of 0.366 ± 0.02 mg/ml and 0.209 ± 0.12 mg/ml, respectively

compared to pure drug (0.196 ± 0.04 mg/ml). But in both the cases, because

of needle shaped crystals with sticky nature, poor flow property and

compressibility, it was omitted from the further study.



Pelletization, CCA and cogrinding were found effective techniques

which not only improved the solubility and dissolution, but also improved

physico-mechanical properties of Chlorzoxazone. Hence, these techniques

were applied in order to get directly compressible material with a good flow

property.

4.3.6 PREPARATION OF PELLETS OF CHLORZOXAZONE

The pellets of Chlorzoxazone were prepared as per the procedure

described in section 4.2.2.1. Here, liquid paraffin (light) was utilized as an

external phase. Drug and excipient(s) like PEG 400, PVP K30 (PVP), HPC,

ethyl cellulose (18 to 22 cps), HPMC E50LV, eudragit RS100, NaCl, talc, etc

were co dissolved (total polymer was 10% w/w of the drug) with drug (1 gm)

either alone or in combination in 20 ml internal phase (acetone). Moreover,

there was a lump formation below around 400 RPM and above which the

pellets were breaking. So, 400 RPM was kept constant for all the further

studies. There was no pellet formation in absence of excipient(s).

The pellets obtained in preliminary trials were subjected to the

evaluation of angle of repose, carr’s index, hausner’s ratio and crushing

strength. On the basis of these parameters, types and concentrations of

various excipients were optimized. Some batches were rejected during

preliminary trials due to poor crushing strength.

During preliminary trials, ethyl cellulose improved crushing strength

with poor flow. Hence, ethyl cellulose was fixed as one polymer by changing

another type of polymers in various concentration ratios in order to improve

shape of pellets. Out of all the above mentioned excipients, only HPMC

E50LV proved to give good flow and strength to pellets. Hence, it was

concluded that HPMC E50LV was the key polymer which could alter the

crystal habit and provided a spherical shape to the pellets. It might be

because of adsorption of HPMC at the growing surface and controlling or

blocking the rate/growth of crystal formation.(94-96)

One more observation was made that, only gummy or rubbery

polymers alone could not be effective in pellet formation. But only the



combination of rubbery long chain polymer like HPMC and a rigid polymer like

ethyl cellulose formed pellets of drug.

Further trials were continued by keeping the ethyl cellulose: HPMC

(K4M, K15M and K100M) as a polymer in various weight ratios (0:100 to

100:0) by keeping total quantity of polymer as fixed (10% w/w of drug) to

study the effect of various grades of HPMC on pellet formation, but it was

observed that pellets formation was possible only in the following weight

combinations as shown in Figure 21 below. The results showed that in many

cases, a lump mass was sticking at the bottom of container and hence, HPMC

E50LV was finally decided as a polymer in combination with ethyl cellulose

(18-22 cps).

Following figure shows effect of various viscosity grades of HPMC on

shape of pellets.

Figure 21: Shape of pellets prepared from various grades of HPMC



Figure 22: Pellets of Chlorzoxazone using combination of ethyl

cellulose: HPMC E50LV (50: 50)

Figure 22 reveals the formation of pellets prepared from the

combination of ethyl cellulose and HPMC in 50:50 ratio.

In this technique of pellet formation, acetone uniformly diffused out of

the droplet and got miscible with light liquid paraffin. Hence, the dissolved

substances in suspended droplet (drug and excipient) got recrystallized

equally by giving a spherical shape to the particle.(97)

In case of higher grade HPMC, diffusion of acetone into liquid paraffin

could not remain equal from all the directions due to highly viscous drop of

internal phase, resulted in irregular shape of pellet.

After confirming HPMC E50LV, five different combinations of ethyl

cellulose: HPMC in mg (from 50:50 to 90:10) were selected for pellet

formation and evaluated. Based on these evaluation parameters like angle of

repose (20.3 0.03 to 26.6 0.83), percentage carr’s index (16.67 0.45 to

21.34 0.05), hausner’s ratio (1.12 0.21 to 1.26 0.24) and crushing

strength in gram (22.53 0.88 to 41.39 0.47), three levels were selected

from each polymer and applied for 32 full factorial design as shown in Table

27.

4.3.6.1 32 full factorial design for preparing pellets of Chlorzoxazone

After conducting various evaluation studies of pellets by combining

both the polymers, 32 full factorial design was selected. Finally, HPMC E50LV



and ethyl cellulose (in different ratios) as per the 32 full factorial design were

co-dissolved in 10 ml acetone and drug (1.0 gm) was dissolved in this

solution. The resulting solution was emulsified within the oil phase, comprising

of light liquid paraffin (500 ml) and continuously agitated using remi magnetic

stirrer at 400 RPM for 25 min. The prepared pellets were separated from

liquid paraffin by keeping the filter paper on a sieve and poured the liquid

containing pellet on it. The collected pellets were washed three to four times

with n-hexane to remove residual organic liquid or liquid paraffin. Finally,

pellets were dried (air dried) for 24 h and stored in desiccators containing self

indicating silica crystals for 1-2 weeks and stored in air tight screw cap glass

bottle. The Table 28 for factorial design containing variables and their levels is

shown.

The design generated by keeping ethyl cellulose (X1) and HPMC

E50LV (X2) as factors and then further levels were also selected. Selection of

linear co-relation with two levels were somewhat confusing, hence three

levels were chosen in order to get linear co-relations. Thus, as per the 32

design, total 9 batches were prepared. The three levels (-1, 0, +1) were

selected for both the factors [EC (X1) and HPMC E50 LV (X2)] by keeping their

concentration different. The levels and design is in following table.

Table 27: Final batches of 32 full factorial design

Batch No. X1 X2 X1 (mg) X2 (mg)

1 -1 -1 50 10

2 -1 0 50 30

3 -1 1 50 50

4 0 -1 70 10

5 0 0 70 30

6 0 1 70 50

7 1 -1 90 10

8 1 0 90 30

9 1 1 90 50



Table 28: Factors and levels of 32 full factorial design

Variables/Levels -1 (Low) 0 (Medium) 1 (High)

X1 (in mg of Ethyl Cellulose) 50 70 90

X2 (in mg of HPMC E50LV) 10 30 50

For each batch of factorial design, dependent variables selected were

Shape factor, Carr’s index and particle Size. The design was formulated to

expect i) CI: carr’s Index between 15 to 18%, ii) SF: Shape factor between

0.950 to 1.0, iii) MD: mean diameter between 0.5 to 0.8 mm.

4.3.7 PREPARATION OF CCA OF CHLORZOXAZONE

4.3.7.1 Selection of good and poor solvent for Chlorzoxazone

Solubility study of Chlorzoxazone was done as per the procedure

described in section 4.2.3.1 in order to obtain good and poor solvent for the

preparation of CCA of Chlorzoxazone. The solubility results are shown in

Table 29 below.

Table 29: Solubility values of Chlorzoxazone in various solvents.

Sr.

No. Solvent

Solubility

(mg/ml)

Mean ± S.D.*

Sr.

No. Solvent

Solubility

(mg/ml)

Mean ± S.D.*

1 Ethanol 257.88 ± 0.031 9 Cyclohexane 59.88 ± 4.61

2 Hexane 0.58 ± 0.509 10 Octanol 30.61 ± 0.012

3 Propanol 266.67 ± 0.350 11 Pet. Ether 10.58 ± 0.031

4 DMF 486.67 ± 4.140 12 Chloroform 5.75 ± 0.015

5 Methanol 351.52 ± 0.764 13 DCM 5.42 ± 0.011

6 Ethyl

Acetate 336.36 ± 0.382 14 Toluene 3.09 ± 0.052

7 Acetone 216.06 ± 2.22 15 CCl4 0.78 ± 0.041

8 n-Butanol 114.55 ± 0.127 16 Distilled

water 0.21 ± 0.063

*Each reading is mean ± S.D. of three readings.



From the above Table 29, it was observed that, the drug was having

good solubility in DMF and acetone. Distilled water as well as hexane showed

poor solubility of drug. Hence, former were selected as good solvents and

later were as poor solvents for the maximum recrystallization of drug.

4.3.7.2 Method of preparation of CCA of Chlorzoxazone

The drug was dissolved in good solvent (DMF or acetone) and added

drop wise to the bad solvent (water or hexane) which was being stirred by

using four blade mechanical stirrers. Excipients used in the preparation of

agglomerates were PVP K30, PEG 400, eudragit S100, HPC LF, EC, purified

talc etc, which were co dissolved either in good or poor solvents alone or in

combinations and CCA were prepared at 400 RPM as described in section

4.2.3.2.

The study revealed poor or negligible agglomeration in absence of

additives (control batch). Preliminary trials were conducted with various

excipients in various concentrations ranging from 0.5% to 2.0% w/v of the

saturated solution of drug in acetone or DMF. The solution of drug-excipients

in good solvent was added drop wise into poor solvent like hexane or water

with constant stirring. The combinations of various excipients were also used

where the concentration of one was kept constant (which gave good results at

that particular concentration) while varying concentration of second excipient.

The agglomerates obtained in preliminary trials were subjected to the

evaluation of angle of repose, carr’s index, hausner’s ratio and crushing

strength (Table 30 and 31). On the basis of these parameters, types and

concentrations of various additives were optimized. Some batches were

rejected during preliminary trials. Although, presence of excipient(s) improved

the flow of the co-agglomerates as compared to pure drug and control batch,

significant results were not found with all the additives. Various combinations

of the additives were also tried and not all but some of them produced co-

agglomerates with remarkable improvement in micromeritic and mechanical

properties. Various batches prepared with and without excipient(s) and their

combinations are given below in Table 30 and 31 with their inferences.



Table 30: Preliminary trials for preparation of CCA of Chlorzoxazone

Trials Good/ Poor

Solvent

Excipient (s) Inference

T1 DMF / Dist.

Water

--

Very poor

agglomeration,

not considerable

T2, T3 DMF / Dist.

Water

HPC LF (0.5 or 1.0% w/v)

T4, T5 DMF / Dist.

Water

PVP K30 (0.5/1.0% w/v)

T6 Acetone/

Hexane

-- No agglomeration

T7 to

T9

Acetone/

Hexane

PVP K30

(0.2/0.5/ 1.0% w/v)

No or partial

agglomeration with

fines in major

quantity

T10 Acetone/

Hexane

PVP K30 (2.0% w/v) Appeared as good

agglomerates

T11,

T12

Acetone/

Hexane

PVP K30 (1.0% w/v) + PEG

400

(0.5/1.0% w/v)

Slightly

agglomerating

T13 Acetone/

Hexane

PVP K30 (2.0% w/v) +

PEG 400 (1.0% w/v)

Appeared as good

agglomerates

T14 Acetone/

Hexane

PVP K30 (2.0% w/v) +

PEG 400 (2.0% w/v)

T15 Acetone/

Hexane

Eudragit S100 (1.0% w/v) Uneven particles +

Fines (In major

amount) T16 Acetone/

Hexane

PVP K30 (1.0% w/v) + HPC

LF (1.0% w/v)

On the bases of above trials, it was seen that Batch no. T-10, T-13 and

T-14 gave good agglomeration. Hence, PVP K30 (2.0% w/v) and PEG 400

(2.0% w/v) were kept constant at 400 RPM. Moreover, in all the improved



batches, acetone and hexane were kept as good and poor solvents,

respectively. Further addition of another excipient(s) was studied to get more

improved agglomerates with good flow and crushing strength. Here, few

conditions now kept constant for further study were,

Table 31: Optimization of excipients combination for CCA of

Chlorzoxazone

Trials Good/ Poor

Solvent Excipient (s) Inference

T17,

T18

Acetone /

Hexane

PVP K30 (2.0% w/v) + PEG

400 (2.0% w/v) +

EC (0.5 / 1.0% w/v)

Fines obtained in

major proportion

which reduced with

increase in

concentration of

ethyl cellulose

T19

PVP K30 (2.0% w/v) + PEG

400 (2.0% w/v) + EC (2.0%

w/v)

Good

agglomeration

T20

PVP K30 (2.0% w/v) + PEG

400 (2.0% w/v) + Talc (0.5%

w/v)

Lump formation

T21

PVP K30 (2.0% w/v) + PEG

400 (2.0% w/v) + Talc

(1.0/2.0% w/v)

Agglomeration was

found initially. Lump

formation occurred

when stirring was

stopped. T22

PVP K30 (2.0% w/v) + PEG

400 (2.0% w/v) + Talc (2.0%

w/v)

T23,

T24

PVP K30 (2.0% w/v) + PEG

400 (2.0% w/v) + Eudragit

S100 (1.0/2.0% w/v)

Small

agglomerates +

Fines

T25

PVP K30 (2.0% w/v) + PEG

400 (2.0% w/v) + HPC LF

(1.0% w/v)

Uneven

agglomerates



On the bases of these preliminary trials, few batches (bold in above

Table 30 and 31) were selected for further evaluation.

4.3.8 PREPARATION OF CO-GROUND SAMPLES OF

CHLORZOXAZONE

In ball mill, the milling intensity i.e. the momentum or the kinetic energy

transferred by the balls to the unit mass of powder per unit time was adjusted

in order to get proper crushing of the powder and improvement in dissolution

of this coground powder might be possible by making it fully or partially

amorphous.(98)

It was found that when the rotation speed of ball mill was kept at lower

RPM, the balls were falling down before powder. Proper mixing and milling

was not observed here. When the speed was kept at higher RPM, the powder

was rotating towards the direction of the shell, causing improper mixing and

grinding. So, the RPM was quite optimized where the powder and balls were

found to fall simultaneously with proper mixing and grinding process together.

The coground samples were prepared as per the procedure described

in section 4.2.4.1. Various excipients like kaolin, HPMC E50LV, neusilin US2,

PVP K30 and PEG 4000 were tried by taking drug: excipient weight ratio 1:1

to 1:5, but the ratio below 1:3 did not show any dissolution improvement in

drug. Five small balls (Outer diameter = 19.04 mm) and five large balls (Outer

diameter = 25.37 mm) made of stainless steel were used to perform the ball

milling operation.

The grinding was done primarily for one hour at 65 RPM to allow

significant attrition with some impact in order to optimize the suitable excipient

for further studies. No increase in the temperature of the milled material was

detected at the end of the process. The cumulative percentage drug release

from pure drug and samples were studied and shown in Figure 23 below. The

pure drug was also ground (control batch) for one hour in order to study the

effect of grinding on crystallinity of drug.



0 20 40 600

20

40

60

Pure drug Drug: Kaolin (1:3) Drug: Kaolin (1:5) Drug: HPMC (1:3)

Drug: HPMC (1:5) Drug: PVP K30 (1:3) Drug: PVP K30 (1:5) Drug: Neusilin (1:3)

Drug: Neusilin (1:5) Drug: PEG 4000 (1:5)Drug: PEG 4000 (1:3) Control batch

Time, min.

CP

R

Figure 23: Dissolution profile of Chlorzoxazone after grinding for one h

with different excipients

From the above figure, it was found that the milling of drug with PEG

4000 (1:3 and 1:5 ratios) showed maximum improvement in dissolution profile

(57.55 0.51 and 64.6 0.84%, respectively) compared to pure drug (37.55

0.22%), control batch (42.58 0.53%) and all other carriers as shown in

above figure.

Thus, milling was continued with PEG 4000 by taking ratio of drug to

PEG 4000 in 1:3 for longer period of time and sampling was done at fixed

intervals (at every hour) to test the in-vitro dissolution till the dissolution rate

was improved. The milled material was sieved through sieve no. 30 (600 μm

opening). To ascertain the effect of method or excipient(s)/carrier(s) or both

on the dissolution rate, Chlorzoxazone alone was ground for extended period

of time. All samples were stored in glass vials at room temperature until used

for further analysis. One batch from optimized sample was also kept for three

months stability study in screw capped container.(99) The physical mixture of

Chlorzoxazone and excipient(s)/carrier(s) were obtained by simple blending in

a 1:3 w/w ratio (drug: carrier) in a V-cone blender to ensure the proper mixing



of powders. Coground mixture of Chlorzoxazone: PEG 4000 (1:3) was also

evaluated for other parameters to study micromeritic and mechanical

parameters.

4.3.9 EVALUATION PARAMETERS OF PELLETS, CCA AND

COGROUND SAMPLES OF CHLORZOXAZONE

4.3.9.1 Packability and flow parameter study of pellets, CCA and


The packability and flow parameters for pure drug, pellets, CCA and

coground mixtures of Chlorzoxazone were studied as per the procedure

described in section 4.2.5.1. In case of pellets, encouraging results of flow

properties and compressibility parameters attributed to the shape towards

sphericity.(84)

Table 32: Packability and flow parameter study of Chlorzoxazone pellets

Batch No.

X1 X2

Angle of Repose, degree ±

S.D.*

Hausner’s ratio ± S.D.*

Carr’s Index,% ±

S.D.*

Kawakita Constants

Kuno’s Constant

a 1/b K

Pure

drug 43.60 ± 0.45 1.43 ± 0.02

37.14

± 0.2 0.05 1.29 0.32

1 -1 -1 24.68 ± 0.33 1.22 ± 0.33 17.31 ± 2.26 0.03 0.24 0.96

2 -1 0 26.03 ± 0.51 1.25 ± 0.51 18.51 ± 3.32 0.03 0.24 0.96

3 -1 1 22.8 0.23 1.25 0.19 19.23 0.11 0.04 0.09 1.12

4 0 -1 21.84 ± 0.58 1.02 ± 0.58 15.53 ± 3.06 0.04 0.15 0.82

5 0 0 20.3 0.03 1.19 0.04 18.33 0.72 0.02 0.27 0.97

6 0 1 27.29 ± 0.55 1.28 ± 0.55 19.06 ± 2.74 0.05 0.34 0.99

7 1 -1 26.6 0.83 1.12 0.21 16.67 0.45 0.03 0.37 1.09

8 1 0 30.10 ± 1.02 1.19 ± 1.02 19.66 ± 1.43 0.03 0.61 0.99

9 1 1 29.05 ± 0.61 1.24 ± 0.61 20.73 ± 0.96 0.03 0.24 0.76




The results of flow property study for pellets in the Table 32 showed a

marked improvement in flow property in all the batches. Thus, presence of

suitable additives was required to produce pellets with spherical shape and

smooth surface to provide excellent flow and compaction. Smaller value of

parameter ‘a’ and ‘1/b’ in kawakita’s equation for the pellets indicated higher

packabilities of the pellets compared to pure drug.(46) The higher the values of

parameter ‘K’ in Kuno’s equation for pellets attributed to the much higher rate

of their packing processes than that of pure drug crystals.(22) The results

indicated remarkable improvement in flowability and packability of pellets

attributed to increased particle size and sphericity.(100, 101)

In case of CCA, some excipients, with their particular concentration,

showed remarkable reduction in carr’s index, hausner’s ratio and angle of

repose of CCA as compared to drug and control batch (Table 33). This was

due to spherical shape and smooth surface impartment to the agglomerates

during the process.(84) These batches were optimized for further study.

Table 33: Packability and flow parameter study of CCA of Chlorzoxazone

Batch Excipients

(w/v)

Angle of

Repose ±

S.D. *

Carr’s

Index (%) ±

S.D. *

Hausner’

s Ratio ±

S.D. *

Kawakita

Constants

Kuno’s

Constant

a b 1/b K

Pure drug 43.6 ±0.45 37.14 ± 0.2 1.43 ±0.02 0.49 0.10 9.9 0.32

Control

batch 38.94 ± 1.0 24.21 ± 0.35 1.39 ±0.12 0.28 0.22 4.52 0.75

T10 PVP K30

(2.0%) 21.2 ±0.31 15.33 ± 0.41 1.17 ±0.26 0.18 0.28 3.52 0.80

T13

PVP K30

(2.0%) +

PEG 400

(1.0%)

18.3 ±0.41 13.51 ± 0.36 1.12 ±0.35 0.19 0.13 7.7 0.76

T14

PVP K30

(2.0%) +

PEG 400

(2.0%)

18.4 ±0.27 15.72 ± 0.61 1.14 ±0.25 0.20 0.55 1.83 0.96

T19 PVP K30

(2.0%) + 19.01±0.63 14.56 ± 0.52 1.10 ±0.31 0.19 0.46 2.18 0.96



PEG 400

(2.0%) +

EC (2.0%)

T24

PVP K30

(2.0%) +

PEG 400

(2.0%) +

Eudragit

S100

(2.0%)

29.5 ±0.52 23.46 ± 0.22 1.29 ±0.45 0.18 0.96 1.04 1.12


Batch T-19 in the above Table 33 showed a remarkable improvement

in packability parameters. It was observed that the angle of repose in

presence of ethyl cellulose (T-19) was slightly increased, which indicated that,

presence of made the particle slightly rough from outer surface, but still the

flow property of pellets was good (T-19, = 19.01) because of sphericity. The

results also indicated that improvement in packability of co-agglomerates

attributed to the increased particle size and sphericity.(100, 101)

The following Table 34 shows flow property and packing parameters of

cogroung mixture of drug: PEG 4000 in 1:3 ratio. Here, during grinding

process, the mixture was decided to evaluate for micromeritic and mechanical

parameters. Hence, the samples after 3 h and 6 h grinding were selected for

further evaluations.

Table 34: Packability and flow parameter study of coground mixtures of

Chlorzoxazone with PEG 4000

Sample

Angle of

Repose ±

S.D. *

Carr’s

Index (%)

± S.D. *

Hausner’s

Ratio ±

S.D. *

Kawakita

Constants

Kuno’s

Constant

a b 1/b K

Pure drug 43.60 ± 0.45 37.14 ± 0.2 1.43 ± 0.02 0.49 0.10 9.9 0.32

Control

batch

After

3 h

41.28 ± 0.13

38.31 ± 1.2

1.51 ± 1.63

0.45

0.22

4.55

0.74

After

6 h 40.06 ± 1.03 38.24 ± 0.5 1.47 ± 0.85 0.47 0.28 3.57 0.74



Coground

mixture

Drug:

PEG 4000

(1:3)

weight

ratio

After

3 h 17.04 ± 1.12 13.4 ± 0.32 1.11 ± 0.22 0.26 0.41 2.43 1.08

After

6 h 19.88 ± 1.05

14.96 ±

0.72 1.21 ± 1.05 0.29 0.37 2.7 0.96


Perusal from the above table showed that the flow property and

packability of coground mixture was improved compared to pure drug and

control batch. This was due to the presence of flowable and plastically

deformation behavior of PEG 4000.(102)

4.3.9.2 Capillary melting point study of pellets, CCA and coground

samples of Chlorzoxazone

The melting range of pure drug, pellets, CCA and coground mixture

were determined as described in section 4.2.5.2.

Preliminary characterization of pellets, CCA and coground mixture of

Chlorzoxazone was performed with capillary melting point observation. A

melting range of Chlorzoxazone (197 to 204 C), pellets (196 to 199 C) and

CCA (197 to 200 C) showed almost similar results, which was an indication

of absence of any formation of new phase. The melting range of all the

samples of coground mixtures was observed between 51 to 54 C. This was

due to presence of large proportion of PEG 4000, which might dissolve the

drug in it during heating.(103, 104)

4.3.9.3 Microscopic determination and surface topography of pellets,

CCA and coground samples of Chlorzoxazone

The crystal morphology of pure drug, pellets, CCA, its control batch

and coground mixture was observed under optical microscope as described in

section 4.2.5.3. As shown in Figure 24 below, shape of pure drug crystals was

like needle, plates and rods with more quantity of fines resulting in more

electrostatic charges which ultimately lead to very poor flow.(50)



Photomicrographs of various batches of pellets and CCA showed

marked improvement in the surface morphology and sphericity compared to

pure drug. Here, the polymers improved sphericity as well as surface

smoothness. These improvements lead to improved flow of pellets due to

reduced interparticulate friction.(105)

Figure 24: Photomicrograph of all the factorial batches of pellets

CCA prepared without use of additives showed poor aggregation and

more amounts of fines (needles) with fluffy nature (Figure 25) resulted in

hindered flow and poor handling properties.



Figure 25: Photomicrographs of optimized batches of CCA and control

batch

The coground mixture of drug: PEG 4000 (1:3 in weight ratio) showed

reduction in particle size compared to pure drug (Figure 26) which might help

the drug to dissolve faster due to larger surface area. At the same time,

sample after grinding for 6 h showed slight aggregation.

Figure 26: Photomicrograph of coground mixture of drug: PEG 4000

4.3.9.4 Drug loading efficiency and % yield of pellets, CCA and coground

samples of Chlorzoxazone(48)

The drug loading efficiency and % yield were measured as per the




The average percentage yield of pellets, CCA and coground mixture

(1:3) obtained was in the range of 93.94%, 91% and 86% (after 6 h),

respectively. The average drug content (loading) in pellets, CCA and

coground mixture (1:3) was 95.26%, 90.84% and 24.43% (after 6 h),

respectively. The results indicated good loading efficiency and %yield.

4.3.9.5 Micromeritic study

Micromeritic parameters study like geometric mean diameter (dg) and

aspect ratio (AR) were performed using optical microscopy method as per the


Pellets and CCA of Chlorzoxazone showed mean diameter for all the

batches in the range of 0.304 to 0.81 mm and 0.6 to 1.04 mm, respectively. It

showed around 05 to 20 folds increment in the size compared to pure drug

(0.06 mm). It indicated that the original crystals of the drug were uniformly

agglomerated. The aspect ratio (AR) of pellets and CCA was obtained in the

range of 1.15 to 1.35 and 1.14 to 1.9, respectively. This modified habit of

pellets and CCA with least AR was an indication of better flow property.(51)

4.3.9.6 Sphericity determination of Chlorzoxazone pellets and CCA

Shape factor (SF) and circularity factor (CF) for control batch and

prepared samples (Table 35) were measured as per the procedure described

in section 4.2.5.6. It was observed from the shape and circulatory factors that,

in the case of pellets, as the amount of HPMC increased, roundness was also

increased. At the same time, in CCA, presence of ethyl cellulose and eudragit

polymers lowered the value of shape factor and circulatory factors.(17) Overall,

the shape and circularity factors were near to unity (equal to 01). This was an

indication of smooth and spherical surface, which imparted good flow and

compressibility.(51)



Table 35: Shape and circularity factors of pellets and CCA

Sr.

No. Sample

Shape factor

(SF)* ± S.D.

Circulatory factor

(CF)* ± S.D.

Pellets

EC HPMC

1 -1 -1 0.978 ± 0.0104 1.032 0.02

2 -1 0 0.989 ± 0.0252 1.035 0.51

3 -1 1 0.993 ± 0.0258 1.041 0.33

4 0 -1 0.963 ± 0.0202 0.997 1.52

5 0 0 0.97 ± 0.0120 1.013 0.06

6 0 1 0.988 ± 0.0328 1.021 0.12

7 1 -1 0.955 ± 0.0365 0.996 0.05

8 1 0 0.972 ± 0.0160 0.998 0.18

9 1 1 0.981 ± 1.5 1.041 0.37

CCA

Control batch 0.786 ± 0.112 0.815 ± 0.0308

T10 PVP K30 (2.0% w/v) 1.013 ± 0.0234 0.997 ±0.0578

T13 PVP K30 (2.0% w/v) +

PEG 400 (1.0% w/v)

0.9722 ± 0.0130 1.020 ± 0.0873

T14 PVP K30 (2.0% w/v) +

PEG 400 (2.0% w/v)

0.9844 ± 0.03612 1.033 ± 0.0551

T19 PVP K30 (2.0% w/v) +

PEG 400 (2.0% w/v) +

EC (2.0% w/v)

0.9571 ± 0.0205 0.995 ± 0.0491

T24 PVP K30 (2.0% w/v) +

PEG 400 (2.0% w/v) +

Eudragit S100 (2.0% w/v)

0.897 ± 0.0494 0.853 ± 0.0629




4.3.9.7 Crushing strength of Chlorzoxazone pellets and CCA

The crushing strength of pellets and CCA of Chlorzoxazone was

measured as per the procedure described in section 4.5.6.7. The value of

crushing strength is given in Table 36.

Table 36: Crushing strength of pellets and CCA

Sr. No. Sample Crushing strength ± S.D.*

(gm)

Pellets

EC HPMC

1 -1 -1 39.55 ± 1.5

2 -1 0 36.26 ± 0.49

3 -1 1 39.17 1.05

4 0 -1 43.27 ± 2.33

5 0 0 27.23 0.55

6 0 1 39.39 ± 0.75

7 1 -1 22.53 0.88

8 1 0 38.88 ± 0.87

9 1 1 39.71 ± 0.61

CCA

T10 PVP K30 (2.0% w/v) 51.283 ± 1.833

T13 PVP K30 (2.0% w/v) +

PEG 400 (1.0% w/v)

52.540 ± 1.680

T14 PVP K30 (2.0% w/v) +

PEG 400 (2.0% w/v)

50.312 ± 2.114

T19 PVP K30 (2.0% w/v) +

PEG 400 (2.0% w/v) + EC (2.0% w/v)

55.781 ± 0.943

T24 PVP K30 (2.0% w/v) +

PEG 400 (2.0% w/v) +

Eudragit S100 (2.0% w/v)

40.013 ± 1.199




As shown in the above Table 36, the crushing strength of batch no. 4

and T-19 was maximum among all the other batches of pellets and CCA,

respectively. This could be attributed to the increased agglomeration of

crystals with good bridging due to presence of suitable polymers.(106)

Improved crushing strength of the particles revealed the improvement in

mechanical and handling properties.(79) This was due to increased cohesive

interaction between particles caused better binding and close packing

between crystals.(106)

Selection of optimized batch

Here, in case of pellets and CCA, all the batches showed good flow

properties as well as shape parameters. But T-19 in case of CCA showed

excellent crushing strength. It was an indication of good handling property.

Hence, batch T-19 for CCA was selected for the further analysis.

In case of coground sample of drug: PEG 4000 (1:3), mixture after 3 h

grinding showed good flow, packability parameters and morphological

behavior compared to ground sample after 6 h. Hence, drug: PEG 4000 (1:3)

mixture after 3 h grinding was optimized for further evaluations.

Optimization for pellets with desired responses was done using surface

response methodology(107-109) where, amount of ethyl cellulose and HPMC

were chosen as independent variable, where as shape factor, mean diameter

and carr’s index were selected as dependent variables. Data for factorial

batches are shown in Table 37 below.



Table 37: Responses of factorial batches of Chlorzoxazone pellets

Batch

No.

Amt. of

ethyl

cellulose,

mg

X1

Amt. of

HPMC

E50LV,

mg

X2

Shape factor,

SF ± S.D.*

Carr’s

Index,

CI ± S.D.*

(%)

Mean

diameter,

mm ± S.D.*

1 -1 (50) -1 (10) 0.978 ± 0.0104 17.31 ± 2.26 0.959 0.12

2 -1 (50) 0 (10) 0.989 ± 0.0252 18.51 ± 3.32 0.987 0.36

3 -1 (50) 1 (10) 0.993 ± 0.0258 19.23 0.11 1.2 0.03

4 0 (70) -1 (30) 0.963 ± 0.0202 15.53 ± 3.06 0.751 0.51

5 0 (70) 0 (30) 0.97 ± 0.0120 18.33 0.72 0.774 0.43

6 0 (70) 1 (30) 0.988 ± 0.0328 19.06 ± 2.74 0.87 0.11

7 1 (90) -1 (50) 0.955 ± 0.0365 16.67 0.45 0.633 0.32

8 1 (90) 0 (50) 0.972 ± 0.0160 19.66 ± 1.43 0.705 0.06

9 1 (90) 1 (50) 0.981 ± 1.5 20.73 ± 0.96 0.785 0.27


A stepwise multivariate linear regression was performed to evaluate

the observations. The statistical evaluation of the results was carried out by

analysis of variance (ANOVA) using Microsoft Excel Version 2007.

The equations representing the quantitative effect of the formulation

variables on the measured responses are shown below:

1. Shape Factor, SF =

0.9741-0.00867X1+0.011X2+0.00433X12-0.0006X2

2+0.0028X1X2

2. Carr’s Index, CI =

18.1367+0.335X1+1.585X2+1.045X12-0.745X2

2+0.535X1X2

3. Mean Diameter, mm =

0.7688-0.1705X1+0.0853X2+0.0798X12+0.0443X2

2-0.022X1X2



Coefficients with one factor (X1 or X2) represent the effect of that

particular factor, while the coefficients with more than one factor (X1X2) and

those with second-order terms (X12 or X2

2) represent the interaction between

those factors and the quadratic nature of the phenomena, respectively. A

positive sign in front of the terms indicates a positive effect, while a negative

sign indicates a negative effect of the factors.

The fitted polynomial equations (full and reduced model) relating the

responses to the transformed factors are shown in the following Table 38. The

polynomial equations could be used to draw conclusions after considering the

magnitude of coefficient and the mathematical sign it carried, i.e., positive or

negative. The significant factors in the equations were selected using a

stepwise forward and backward elimination for the calculation of regression

analysis. The terms of full model having non-significant p value (p>0.05)

showed negligible contribution in obtaining dependent variables and thus are

neglected.(110)

Table 38: Results of regression analysis of factorial batch of

Chlorzoxazone pellets

Response, SF b0 b1 b2 b12 b2

2 b12 R2

FM 0.9741 -0.0087 0.011 0.0043 -0.0006 0.0028 0.9652

RM 0.9766 -0.0087 0.011 -- -- -- 0.9119

P 5.7E-08a 0.0118a 0.0060a 0.2111 0.8231 0.2500 --

Response, CI b0 b1 b2 b12 b2

2 b12 R2

FM 18.14 0.335 1.585 1.045 -0.745 0.535 0.9828

RM 17.64 0.335 1.585 1.045 -- -- 0.8729

P 6.2E-06a 0.0968 0.0014a 0.0231a 0.0547 0.0526 --

Response, mm b0 b1 b2 b12 b2

2 b12 R2

FM 0.7688 -0.171 0.085 0.079 0.044 -0.022 0.9806

RM 0.8516 -0.1705 0.0853 -- -- -- 0.9034

P 0.0001a 0.0018a 0.0131a 0.0645 0.2104 0.3416 --

FM: Full model, RM: Reduced model, a Regression coefficients, statistically significant (P<0.05)



Table 39: The results of ANOVA*

Response, SF df(3,3) SS MS F R2

Regression

FM 5 0.0012 0.0002 16.66 0.9652 Fcal = 1.53

RM 2 0.0012 0.0006 31.09 0.9119 Ftab = 9.28

Error

FM 3 4.49 E-05 1.5 E-05

RM 6 0.0001 1.89 E-05

Response, CI df(2,3) SS MS F R2

Regression

FM 5 20.19 4.04 34.20 0.9828 Fcal = 9.12

RM 3 17.94 5.98 11.45 0.8729 Ftab = 9.55

Error

FM 3 0.35 0.12

RM 5 2.61 0.52

Response, mm df(3,3) SS MS F R2

Regression

FM 5 0.24 0.05 30.39 0.9806 Fcal = 3.99

RM 2 0.22 0.11 28.04 0.9034 Ftab = 9.28

Error

FM 3 0.01 0.001

RM 6 0.02 0.004

*ANOVA indicates analysis of variance, df: degrees of freedom, SS: sum of

squares, MS: mean of squares, F: Fischer’s ratio, R: regression coefficient,

FM: full model, RM: reduced model.

Above Table 39 shows the results of analysis of variance (ANOVA),

performed to identify insignificant factors. The critical value (Tabulated) of F

for = 0.05 and the calculated value is shown here where, Ftab is more than

Fcal. This was a conclusion of validation of reduced model.(111) It was

concluded that the interaction terms where P>0.05, did not contribute

significantly to the prediction of desired responses and hence could be

omitted from the full model.



After carrying out the ANOVA and finding out the significant factors

which could affect the responses from prepared pellets, the equations

representing quantitative effect of the formulation variables on the measured

responses are shown below:

1. Shape Factor, SF = 0.9766-0.0087X1+0.011X2 (RM)

2. Carr’s Index, CI = 17.64+0.335X1+1.585X2+1.045X12 (RM)

3. Mean Diameter, mm = 0.8516-0.1705X1+0.085X2 (RM)

The change in responses as a function of X1 and X2 is depicted in the

form of contour and response surface plot based on full factorial design. The

data of all the 9 batches of factorial design were used for generating

interpolated values using Design Expert® Software 8.0.5.2 Trial Program

(Stat-Ease, Inc., Minneapolis, MN). Low level of X1 and high level of X2 were

found to be favorable conditions for obtaining good spherical shape, whereas,

High level of X1 and Low level of X2 was favorable for obtaining low particle

size. For Carr’s index (which should be low), X1 was not much effective in

getting low Carr’s index than X2 because of smaller coefficient of X1 (0.335).



Shape factor

Figure 27 (a): Contour plot for shape factor of pellets

Figure 27 (b): Surface plot for shape factor of pellets



It may be concluded from above Figure 27 (a) and (b) that, by

increasing the amount of HPMC and decreasing the amount of ethyl cellulose

could give good spheres. This might be because, HPMC was the key polymer

which could alter crystal habit and the manner in which drug got recrystallized

by giving a spherical shape. It might be because of adsorption of HPMC at the

growing surface and controlling or blocking the rate/growth of crystal

formation.(94-96)

Carr’s index

Figure 28 (a): Contour plot for carr’s index of pellets



Figure 28 (b): Surface plot for carr’s index of pellets

It can be concluded from the above Figure 28 (a) and (b) that, when

both the polymers were at low level, carr’s index was higher. This might be

because the pellets could not become much spherical as HPMC was the key

polymer which could alter the crystal habit and imparted spherical shape by

adsorbing at the growing surface and controlling or blocking the rate/growth of

crystal formation.(94-96)

As the level of polymers increased, carr’s index decreased up to

certain level and afterwards increased again. Also, It might be concluded from

the above figure and equation that, X2 (HPMC) was more significant (2=1.59)

in increment of Carr’s index (ideally it should be low) than X1 (EC) (1=0.34).

Increment in carr’s index with the amount of HPMC was because of

roughness imparted by HPMC to the surface, which leads to poor flow.



Different surface roughness affected sliding of the particles against

each other, leading to difference in their packing geometry and thus, carr’s

index also. Hence, inter particle friction (due to roughness of the surface)

appeared to influence the initial particle rearrangement, which might be a

reason of increased carr’s index as X2 (HPMC) increased.(62, 112, 113)

Particle Size

Figure 29 (a): Contour plot for particle size of pellets



Figure 29 (b): Surface plot for particle size of pellets

It is depicted from the above Figure 29 (a) and (b) that, amount of

HPMC had positive effect on the size of pellets. As the amount of HPMC

increased, particle size increased. It would be expected that the viscosity of

the polymer mixture would increase (especially presence of HPMC) as

polymer concentration rose, resulted in enhanced interfacial tension and

hence, formation of larger particles.(114)

Validity of equations

From the overlay plot, Check Point Batch (Batch 10) was prepared at

X1 = -0.15 and X2 = -0.19 (Figure 30) and performed practically. It was

determined by Design expert as well as Sigma plot® 11.0 software.



Figure 30 (a): Overlay plot for desirability of responses of pellets

Figure 30 (b): Overlay plot for desirability of responses of pellets



On the basis of criteria for desired response, following batch was

formulated to assess the reliability of the evolved equations. The experimental

values and predicted values of each response are shown in Table 40. The

percentage relative error of each response was calculated using the following

equation:

Percentage Relative Error =

100aluePredictedV

alValueExperimentValue Predicted

The percentage relative errors for check point batch were in the range

of acceptance. It was concluded that the experimental values were in good

agreement with theoretical values. This proved the validity of the equations

and selected factorial design.

Table 40: Comparison between predicted and experimental results

Batch No.

Amt. of

ethyl

cellulose,

mg

X1

Amt. of

HPMC

E50LV,

mg

X2

Shape

Factor,

SF ± S.D.*

Carr’s

Index,

CI ± S.D.*

(%)

Mean

Diameter

(mm)

± S.D.*

Predicted

Value -- -- 0.976 17.56 0.861

Experimental

Value

- 0.15

(67)

- 0.19

(26.0)

0.955

1.11

17.02 ±

1.35

0.812

1.03

% Relative

Error -- -- 2.15 3.08 5.69

*Results are Mean ± S.D. of three observations.

The other micromeritic parameters for check point batch (Batch 10)

were also evaluated and are represented in below Table 41.



Table 41: Evaluation parameters for check point batch (batch 10) of


Sr.

No. Parameter Results

Sr.

No. Parameter Results

1 Melting

range, C

197 - 201 6 Drug loading

efficiency ±

S.D.*

94.53 ± 1.04

2 Angle of

repose,

± S.D.*

18.31 ± 0.52 7 % yield± S.D.* 94.06 ± 0.67

3 Hausner’s

ratio

± S.D.*

1.17 ± 0.08 8 Aspect ratio ±

S.D.*

1.12 ± 0.03

4 Kawakita

Constants

a

0.05

b

9.71

1/b

0.103

9 Circularity factor

± S.D.*

0.985 ± 1.02

5 Kuno’s

Constant, K

0.86 10 Crushing

strength

± S.D.#

42.58 ± 2.18

* and # indicates results of Mean ± S.D. for three and five observations,

respectively.

Figure 31 below shows spherical morphology of pellet prepared from

check point batch.

Figure 31: Photomicrograph of checkpoint batch (batch 10) of




4.3.9.8 Heckel plot study of optimized batch of pellets, CCA and


Accurately weighed quantity of prepared samples (800 ± 5 mg) were

compressed using 8 mm flat faced punch at the constant compression at

different pressures ranging from 3 to 9 tons by keeping 1 min dwell time.(18)

Heckel parameters were calculated as per the procedure described in section

4.2.5.8.

True density was considered as the density of compacts when the

highest pressure applied on the powder (here, 9 tons).(79, 80)

The slop of Heckel plot ‘K’ is indicative of plastic behavior of the

material.(81) Larger the value of ‘K’, greater is the plasticity in material. The

linearity in the graph (Figure 32) was an indication of plastic deformation.

Table 42 below shows parameters of Heckel plot. ‘A’ value of all the samples

was less than pure drug. This finding suggested that, low compression

pressure was required to obtain closest packing of the particle, fracturing its

texture and densifying the fractured particles.(42)

Yield strength (σ0) is an indication of tendency of the materials to

deform either by plastic flow or fragmentation.(83) Low value of yield strength

(σ0) and yield pressure (Py) was again an indication of low resistance to

pressure, good densification and easy compaction.(47) Thus, Heckel plot data

suggested that, all the particles were fractured easily and new surface of

particles produced might contributed to promote plastic deformation under

applied compression pressure.(81)



Figure 32: Heckel plot for Chlorzoxazone and its optimized samples

The table below gives heckel plot parameters for pure drug, pellets,

CCA and coground samples.

Table 42: Heckel plot parameters of Chlorzoxazone samples

Batch

Yield

Pressure

(Py)

Constant

(A)

Slope

(K)

Yield

Strengt

h (σ0)

R2

Pure Drug 26.09 0.9924 0.038 8.7719 0.9724

Pellets Batch 10 1.747 0.5543 0.573 0.582 0.979

T-19 1.23 0.028 0.8132 0.4099 0.8802

Control batch (CCA) 5.928 1.035 0.179 1.8622 0.9783

Coground mixture

after 3 h 2.082 0.6396 0.4803 0.6940 0.9817



Perusal from above Table 42 indicated that, out of all the samples,

CCA (batch T-19) showed maximum compressibility and tableting behavior. In

case of ground sample, effect of PEG 4000 addition (plastic material) on

tableting properties was observed. Densification of this polymer was probably

due to its plastic deformation.(102)

4.3.9.9 Tensile strength measurement of pellets of Chlorzoxazone

samples after heckel analysis

The tensile strength of pellets prepared in heckel study was measured


The maximum tensile strength was obtained at compression pressure

9 ton. The high tensile strength of compacts was an indication of strong

interparticulate bonding between the particles of optimized batch compared to

pure drug as well as control batch.(62)

Figure 33: Pressure – tensile strength relation between Chlorzoxazone

and its prepared samples



The values of tensile strength of pellets (prepared in KBr press)

from Chlorzoxazone pure drug and other samples at 9 ton pressure with 1 min

dwell time is given in Table 43.

Table 43: Tensile strength of Chlorzoxazone pellets after heckel study

Batch Tensile Strength (kg/cm2) ± S.D.*

at 9 ton pressure

Pure Drug 5.708 ± 0.121

Pellets Batch 10 16.498 ± 0.71

T-19 19.256 ± 0.2354

Control batch (CCA) 8.554 ± 0.243

Coground mixture after 3 h 11.689 ± 0.521


In case of coground mixture, during the compression process, surface

melting of compacts of drug containing PEG 4000 might easily occur,

resulting in greater particle bonding and tensile strength. At higher pressures,

melting of the particles and subsequent surface melting of compact became

probable the predominant mechanism for volume reduction.(102)

4.3.9.10 Elastic recovery of pellets of Chlorzoxazone samples after

heckel analysis

The elastic recovery of pellets prepared in heckel study was measured


The result for the elastic recovery for optimized batches is given in the

following Table 44. Elastic recoveries of samples were smaller than that of

original drug crystals. These findings suggest that agglomerated crystals are

easily fractured and the new surface of crystals produced might contribute to

promote plastic deformation under compression.(79)



Table 44: Elastic recoveries (ER) of Chlorzoxazone pellets after heckel

analysis

Batch % Elastic Recovery ± S.D*

for 9 ton

Pure Drug 5.48 ± 0.79

Pellets Batch 10 2.14 ± 1.03

T-19 0.87 ± 0.32

Control batch (CCA) 1.56 ± 0.52

Coground mixture after 3 h 1.08 ± 0.73


Above table showed least elastic recovery in case of CCA, which was

negligible.

4.3.9.11 Aqueous solubility study of coground samples of

Chlorzoxazone

CCA and pellets were not studied for aqueous solubility determination

as the primary goal of CCA and pellets was to enhance the flow property by

binding and/or covering the drug with the help of excipients and also

dissolution rate enhancement.(13, 70, 115)

The solubility of coground samples was done as per the described

procedure in section 4.2.5.11.

Solubility data of Chlorzoxazone and ground drug are shown in the

Table 45 and represented graphically in Figure 34. To perform an errorless

study, pure drug and control batch were premixed with PEG 4000 in the

equivalent quantity of drug loading of coground mixture (24.43% drug). The

solubility of ground drug was found to be high in distilled water and pH 6.8

buffer solutions, where as low in 0.1N HCl. pH 1.2 and pH 4.5 buffer solutions.

The control batch also behaved in the similar manner. The extent of effect of

cogrinding in presence of polymers on solubility of Chlorzoxazone was found

to be greater in coground sample over the solubility of pure drug as well as

control batch too.



Table 45: Solubility data of Chlorzoxazone from pure drug and ground

drug in different solvents

Solvents

Chlorzoxazone solubility (mg/ml)

Mean ± S.D.*

% Chlorzoxazone

solubility

pure drug control

batch

Coground

drug

control

batch

Coground

drug

Distilled

water

1.008 ± 0.05 2.06 ± 0.018 3.12 ± 0.046 204.7 309.9

0.1 N

HCl

0.542 ± 0.06 0.984 ± 0.05 1.89 ± 0.071 181.5 349.1

pH 1.2

buffer

0.55 ± 0.051 0.968 ± 0.02 1.58 ± 0.091 176.6 287.8

pH 4.6

buffer

0.72 ± 0.051 1.143 ± 0.08 2.14 ± 0.028 159.2 297.6

pH 6.8

buffer

1.018 ± 0.01 2.055 ± 0.06 3.24 ± 0.074 201.9 317.9

* indicates the results are the average of three determinations (n=3),

0

1

2

3

Pure drug

Control batch

Coground mixture

Distilled water 0.1 N HCl pH 1.2 buffer pH 4.6 buffer pH 6.8 buffer

Sol

ubili

ty o

f chl

orzo

xazo

ne, m

g/m

l

Figure 34: Solubility of Chlorzoxazone from pure drug, control batch

and coground mixture after 3 h (ratio, 1:3,%w/w) in distilled water, 0.1 N

HCl and buffer solution of pH 1.2, 4.6 and 6.8 (Mean ± S.D.; n=3)



4.3.9.12 Differential scanning calorimetry (DSC) of pellets, CCA and


Thermograms of Chlorzoxazone, excipients and prepared samples

were recorded as described in section 4.2.5.12. Thermal properties of drug

and pellets were studied using DSC (Figure 35). Melting point of drug was

observed at 196.13 oC (Hf= - 431.28 mJ). Melting point peak of drug was

slightly broadened in thermograms of physical mixture as well as pellets. This

might be due to dispersion of crystalline drug into amorphous polymer i.e. EC

and HPMC and was not a sign of pharmaceutical incompatibility.(112, 116, 117)

Partial amorphization of drug in pellets might also be a reason for such

phenomena.(118) Uniformity in crystalline structure was confirmed by

endothermic peaks of drug that remained at almost same temperature in

physical mixture (190.60 oC, Hf= -130.44 mJ) and pellets (190.95 oC, Hf=

-120.86 mJ). One more peak was obtained in pellets at 252.91 oC. This was a

degradation peak of components.

Figure 35: DSC thermogram of A) Chlorzoxazone, B) ethyl Cellulose, C)

HPMC E50LV, D) physical mixture of drug, ethyl cellulose and HPMC

E50LV and E) pellets of Batch 10.



In case of CCA, melting point of drug was observed at 196.13 oC. The

CCA from control batch also showed the same melting peak. Melting point

peak of drug was slightly broadened in thermograms of physical mixture as

well as agglomerates. This might be due to dispersion of crystalline drug into

amorphous polymer i.e. PVP K30 and was not a sign of pharmaceutical

incompatibility.(119) Partial amorphization of drug in agglomerates might also

be a reason for it. Uniformity in crystalline structure was confirmed by

endothermic peaks of drug that remained at almost same temperature in

physical mixture (190.40 oC) and agglomerates (201.02 oC).

Figure 36: DSC thermogram of A) Chlorzoxazone, B) control batch, C)

PVP K30, D) ethyl cellulose, E) physical mixture of drug, PVP K-30, ethyl

cellulose and PEG 400 and F) CCA of batch T-19.

From the Figure 36 in coground mixture of drug: PEG 4000 (1:3% w/w)

after 3 h and 6 h grinding, it was seen that there was no much difference in

the melting endotherm of pure drug Chlorzoxazone (196.13 C) and control

batches (188.4 C) ground at 3 and 6 hours. It was an indication of absence of



any polymorphic transformation. The heat of fusion in case of pure drug

(-431.28 mJ) with compared to control batch at 3 h (-190.07 mJ) and 6 h (-

162.9 mJ) was higher. This might be a reason of somewhat improved

dissolution of control batch than pure drug.(125)

The DSC curves of pure components in Figure 36 (A) and 36 (D) a

single endothermic melting peak for Chlorzoxazone (196.13 °C) and for PEG

4000 (57.26 °C) was observed. The DSC curve of the milled samples Figure

36 (F) and 36 (G) exhibits a melting endotherm of 48.8 °C and 48.95 C,

which was almost the same melting peak of PEG 4000. It was concluded that

Chlorzoxazone slowly dissolved in the PEG 4000 melt and therefore no

distinct endothermic event could be observed for the active compound in the

drug-polymer milled mixture with DSC. A similar result showed the DSC curve

of the physical mixture in Figure 36 (E) where the melting peak of

Chlorzoxazone could not be recorded either due to the slow dissolution of the

Chlorzoxazone in the melt of the carrier on heating and thereafter the

stabilization of solid drug particles in a metastable form.(103, 104)

The peak of PEG 4000 in the DSC curve of the coground samples was

broadened compared to that of pure PEG 4000, which indicated that the

carrier weakly interacted with Chlorzoxazone. Similar observations were

reported by Rodriguez et al.(103) for diclofenac / PEG 4000 systems. Also in

this system, only a broad endotherm could be observed which corresponded

to the monotectic melting (some degrees below the melting peak of the pure

PEG 4000).(103, 104)



Figure 37: DSC spectra of A) pure Chlorzoxazone, B) control batch after

3 h C) control batch after 6 h, D) PEG 4000, E) physical mixture of drug

and polymer in 1:3 ratio, F) coground mixture of drug: PEG 4000 (1:3)

after 3 h and G) coground mixture of drug: PEG 4000 (1:3) after 6 h

As such polymers are not highly ordered and always contain some

'structural voids', it is likely that the amount of the drug that dissolved in the

melt is entrapped in such areas after cooling and crystallizing of the

carrier.(104)

4.3.9.13 Fourier transform Infra-Red (FT-IR) spectroscopy of pellets, CCA

and coground samples of Chlorzoxazone

FT-IR spectra of Chlorzoxazone, excipients and prepared samples

were recorded as described in section 4.2.5.13.

In case of pellets, the FT-IR spectra are shown in Figure 38. The

spectrum of pure Chlorzoxazone in following figure showed the characteristic

peaks at 3158.3 cm-1 (N-H stretch), 3052.24 cm-1 (aromatic hydrocarbon),

1616.3 cm-1 (C=C stretch), 732.09 cm-1 (C-Cl linkage). The spectrum of

HPMC gave characteristic peaks at about 1644.5 cm-1, 1109.8 cm-1 and 1033

cm-1 vibration region.(121) The spectrum of ethyl cellulose showed important



bands at 3478.1 cm-1 (OH stretching vibrations) and the band at around

2979.2 cm-1 (CH stretching vibration).(122)

Figure 38: FT-IR spectra of A) Chlorzoxazone, B) ethyl cellulose, C)

HPMC E50LV, D) physical mixture of drug, ethyl cellulose and HPMC

E50LV and E) pellets of Batch 10

All the peaks of drug were appeared in the physical mixture as well as

pellets (Batch 10), which showed that there was no interaction between drug

and excipients used.

Infrared spectra of pure drug, physical mixture and prepared CCA were

shown in Figure 39. The spectrum of pure drug showed all the characteristic

peaks as discussed in above Figure 38. Spectra of PVP K30 showed

important bands at 2959.4 cm-1 (C-H stretch) and stretching vibration of the

carbonyl group that would typically appear around 1664.4 cm-1. Moreover, a

peak at about 3438.1 cm-1 due to O-H stretching vibrations of absorbed

moisture was seen. The spectrum of ethyl cellulose showed important bands

at 3478.1 cm-1 (-OH stretching vibrations) and the band at around



2979. 2 cm-1 (-CH stretching vibration). All the peaks of drug were appeared in

the physical mixture as well as agglomerates (T-19), which showed that there

was no interaction between drug and excipients used.

Figure 39: FT-IR spectra of Chlorzoxazone and its CCA (T-19)

In case of coground samples of Chlorzoxazone, FT-IR spectroscopy

study of pure Chlorzoxazone in following Figure 40 showed the characteristic

peaks at 3146.68 cm-1 (N-H stretch), 3052.24 cm-1 (Aromatic Hydrocarbon),

1615.69 cm-1 (C=C Stretch), 732.09 cm-1 (C-Cl linkage). FT-IR spectra of PEG

4000 showed peaks at 2950-2750 cm-1 (C-H stretch) and 1466.34 cm-1 (C-H

bending) and 1350-1000 cm-1 (C-O stretching).



Figure 40: FT-IR analysis of A) Chlorzoxazone pure drug, B) ground drug

after 3 h, C) ground drug after 6 h, D) PEG 4000, E) physical mixture of

drug: polymer in 1:3 ratio, F) coground drug with polymer in 1:3 ratio

after 3 h and G) coground drug with polymer in 1:3 ratio after 6 h.

From the above Figure 40, it was seen that all the peaks of

Chlorzoxazone were present in control batch, physical mixture and coground

drug in presence of polymer. Thus, it was concluded that there was no

chemical reaction found between drug and polymer. As well as, there was no

sign of any polymorphic changes.

4.3.9.14 Powder x-ray diffractometry (pXRD) of pellets, CCA and


Powder X-ray diffraction pattern of Chlorzoxazone and prepared

samples were recorded as described in section 4.2.5.14.



Pure drug showed its characteristic peaks with decrease in percent

relative intensity at 2 values of 19.92, 27.489, 12.825, 13.815, 25.233,

17.766 and 25.796, respectively. In case of pellets, x-ray powder diffraction

patterns of pure drug and the optimized batch in the 2θ range of 5˚ to 90˚

showed that the characteristic diffraction peaks of Chlorzoxazone were still

detectable in the pellets (Figure 41). This suggests that the particles

crystallized in the presence of excipients did not undergo structural

modifications. Intensities of characteristic peaks of drug were also reduced in

pellets, which might be due to differences in the crystallinity of the drug and

pellets.(123)

As shown in the Figure 41, all XRD peaks of the pellets were

consistent with the pattern of pure drug crystals, indicated that there was no

polymorphic changes or detection of drug-excipients incompatibility after

recrystallization.(124)

Figure 41: X-ray powder diffraction patterns for Chlorzoxazone pellets



In CCA of Chlorzoxazone also, all XRD peaks were consistent with the

pattern of pure drug crystals, indicated that there was no polymorphic

changes or detection of drug-excipients incompatibility after

recrystallization.(124)

Figure 42: X-ray powder diffraction patterns for Chlorzoxazone CCA

In case of coground mixture of Chlorzoxazone, XRD of Chlorzoxazone

(CHLOR) revealed high intensity reflections with characteristic sharp peaks at

19.92, 27.49, 12.83, 13.82, 25.23, 17.77 and 25.79 (2). The peak at

19.92 (2) was used to compare the XRD patterns. PEG 4000 exhibited a

distinct pattern with diffraction peaks at 23.35 and 19.23 (2). The physical

mixture showed the characteristic peaks of the pure components at identical

angles, which proved that no interactions took place during mixing. All the



peaks were present in the diffractograms of control batches but with very low

intensity than the pure drug powder. Moreover, the same peaks of drug were

also appeared in the coground sample collected at 3 and 6 h, but the intensity

was again very much reduced compared to pure drug. This was almost

amorphous in nature.(125) This indication further supported that there was no

chemical interaction between drug and polymer. Moreover, it also generated

amorphization and enhanced the dissolution properties of drug.(126)

Figure 43: pXRD pattern of coground Chlorzoxazone



4.3.9.15 Scanning electron microscopy (SEM) of pellets, CCA and


The scanning electron microscopy of Chlorzoxazone and prepared

samples was performed as per the procedure described in section 4.2.5.15.

As revealed in the SEM photographs of the pure drug (Figure 44), it

has very sticky and small crystals which hindered the flow.(127)

Figure 44: SEM Photographs of pure drug powder

As shown in the Figure 45 below, pellets (Batch 10) were spherical in

shape which provided good flow. The surface appeared in the image was

rough in nature, may be due to addition of polymer (HPMC). Moreover, the

drug also crystallized on the surface, which gave hindrance in flow.(62, 112, 113)

Figure 45: SEM Photographs of pellets prepared from Batch 10



Figure 46: SEM photographs of external surface of pellets prepared from

Batch 10

The major work of the polymer was to cover the external surface of the

pellets which could be seen from the SEM images (Figure 46). Figure 47

below is showing the broken pellet where, outer surface is smooth and inner

side of the pellets, bundles of drug crystals have been deposited.

Figure 47: Bundles of crystals inside the pellet (Batch 10)



Figure 47 shows platy crystals inside the pellet, which is also

responsible for good compressibility of pellets.(89)

In case of SEM image of CCA, agglomerates from control batch

(Figure 48) showed very loose aggregation and rough surface with bundles of

needle like crystals, which also had very poor flow and compression

properties. The surfaces were comparatively smooth and aggregation was

good when additives like PVP K30, ethyl cellulose and PEG 400 were used

(Figure 49). Due to good agglomeration of crystals and smooth surface, the

CCA prepared with addition of additives had very good flow and compaction

properties as compared to pure drug as well as control batch. Also, the

agglomerates were very porous in nature, which increased an effective

surface area and exposure of inner surfaces to dissolution fluid and ultimately

improved the dissolution to a greater extent.

Figure 48: SEM photographs of control batch of Chlorzoxazone CCA

As shown in Figure 49, CCA are spherical in shape and uniformly

packed due to presence of polymers.



Figure 49: SEM Photographs of Chlorzoxazone CCA (batch T-19)

In the study of cogrinding with PEG 4000, SEM photograph showed

that drug was crystalline in nature at the initial stage. Control batch showed

aggregation of crystals resulting into somewhat bigger particle due to charge

generation.(27)

On grinding in presence of PEG 4000, the particle size was increased.

This might be due to generation of little amount of local heat on grinding,



which melted PEG 4000 to a little extent. Due to this, the polymer dissolved in

a part and adsorbed at the crystalline surface of drug resulting into bigger

particle.(102) This showed increase in amorphization of Chlorzoxazone.(104)

Figure 50: SEM analysis of A) Chlorzoxazone pure drug, B) control batch

at 3 h, C) control batch at 6 h, D) coground CHLOR: PEG 4000 (1:3) at 3

h, E) coground CHLOR: PEG 4000 (1:3) at 6 h

In the above Figure 50 (E), the size of particle was still bigger due to

more layering of PEG 4000 onto the drug crystals.



4.3.10 PREPARATION OF DOSAGE FORM OF

CHLORZOXAZONE AND THEIR EVALUATION

4.3.10.1 Preparation of directly compressible tablets of CCA and


Perusal from Table 42 to 44, it was confirmed that, CCA (batch T-19)

showed excellent tableting properties than pellets of batch 10. Moreover,

CCA showed very high crushing strength compared to pellets, which was an

indication of good handling property. Hence, out of CCA and pellets, CCA

was considered as an ideal to convert into formulation.

In case of coground mixture of drug: PEG 4000 (1:3) after 3 h grinding

also showed good tableting properties.

Hence, CCA from batch T-19 and coground mixture after 3 h were

considered for preparation of dosage form.

Tablets containing 500 mg equivalent to Chlorzoxazone (tablet for pure

drug and CCA) as well as ground mixture equivalent to 125 mg

Chlorzoxazone were prepared by direct compression using different

formulation excipients as shown in Table 45 and 46. CCA and coground

mixture were sieved to achieve similar particle size distribution (# 22 for CCA

and # 80 for coground sample) for each batch and other formulation

excipients were added into it. All the ingredients for tablets prepared from

CCA and coground mixture were weighed separately and mixed properly in

‘V’ cone blender.

The material for each tablet was weighed introduced manually into the

die and compressed in the tablet machine using round-shaped, 15 mm flat,

concave punch for CCA and 6 mm flat, round punch for coground mixture.

The tablets were prepared as per the procedure described in section 4.2.6.1.

Tablets prepared from CCA were containing very less amount of MCC

(Table 45), which was a considerable improvement in the properties of drug

for making directly compressible form. The formulations for tablets and its

evaluations are given in Table 48.



Table 46: Formulation of directly compressible tablet of Chlorzoxazone

from CCA (Batch T-19)

Ingredients Pure drug CCA (T-19 Batch)

Chlorzoxazone, mg 500 532 mg (eq. to 500 mg drug)

PVP K-30, mg 16 --

Ethyl cellulose, mg 16 --

Kyron T-314, mg, (10%) 70 65

Magnesium stearate, mg, (1%) 7.0 6.5

Talc, mg, (2%) 14 13

Aerosil, mg, (0.5%) 3.5 3.25

MCC, mg 160 30.25

Total wt. of tablet, mg 780 650

At the same time, tablets from coground mixture were prepared using

ingredients given in Table 47. Here, PEG 4000 was a directly compressible

material undergoing plastic deformation. MCC was required only as a filler. At

the same time, directly compressible tablets of pure drug required a large

quantity of MCC for good hardness without lamination.

Table 47: Formulation of directly compressible tablet of Chlorzoxazone

from coground mixture (1: 3, % w/w)

Formulation Pure drug Coground mixture

(1:3, % w/w)

Chlorzoxazone, mg 125 511.67 mg (equivalent to 125

mg Chlorzoxazone)

Kyron T-314, mg, (10%) 12 65

Magnesium stearate, mg, (1%) 1.3 6.5

Talc, mg, (2%) 2.5 13

Aerosil, mg, (0.5%) 0.6 3.25

MCC, mg 75 50.58

Lactose, anhydrous, mg 33.6 --

Total wt. of tablet, mg 250 650



4.3.10.2 Evaluation of tablets of Chlorzoxazone

Evaluation parameters were studied as per the procedure described in

sections from 4.2.6.2.1 to 4.2.6.2.5.

The evaluation parameters of prepared tablets are given in following

Table 48.

Table 48: Evaluation parameters of prepared tablets

Sr.

No. Parameters Tablets equivalent of drug from

Pure drug

(500 mg)

CCA

T-19

Pure drug

(125 mg)

Coground

mixture (1:3)

1 Hardness,

kg/cm2 ±

S.D.*

4.5 ± 0.31 7.6 ± 0.52 5.3 ± 0.67 6.8 ± 0.33

2 Friability, % 0.63 0.017 0.51 0.19

3 D.T., sec. ±

S.D.* 8.3 ± 1.23 19 ± 1.41 4.51 ± 1.33 5.26 ± 1.44

4 Diameter,

mm ± S.D.* 12.08 ± 0.004 12.05 ± 0.006 6.01 ± 0.005 6.07 ± 0.003

5 Thickness,

mm ± S.D.* 3.62 ± 0.055 3.37 ± 0.02 3.21 ± 0.01 3.19 ± 0.03

6 Wt.

variation,

mg ± S.D.*

777.2 ± 3.15 648.3 ± 2.56 248.3 ± 2.17 645.7 ± 3.51

* Indicates average of triplicate

4.3.11 DISSOLUTION AND KINETIC STUDY OF PELLETS, CCA

AND COGROUND SAMPLES OF CHLORZOXAZONE AND ITS

DOSAGE FORMS

4.3.11.1 In vitro dissolution of pellets, CCA and coground samples and

dosage forms of Chlorzoxazone

As per the procedure of dissolution study explained in section 4.2.7.1,

dissolution profiles of pure drug and prepared samples (Type – II) as well as

dosage forms (containing equivalent amount of API) (Type - I) were studied.

The dissolution medium was 900 ml buffer phosphate (pH 6.8) equilibrated to



37 ± 0.5 °C. Peddles / baskets were rotated at 50 RPM. The concentrations of

Chlorzoxazone in the solutions were determined by UV spectrophotometer at

280 nm by diluting with phosphate buffer pH 6.8 using same media as blank.

All the determinations were performed in triplicate.

Figure 49 below indicates the extent of dissolution of pellets of factorial

as well as check point batches.

Table 49: Dissolution profiles of pure drug and pellets from factorial

batches

Time,

min.

Cumulative Percentage release S.D.*

Pure

Drug

Batch

01

Batch

02

Batch

03

Batch

04

Batch

05

Batch

06

Batch

07

Batch

08

Batch

09

Check

Point

Batch

0 0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

5 11.59

0.35

24.86

0.61

11.44

2.99

20.59

1.96

22.81

0.96

23.79

0.61

23.64

0.51

23.19

1.45

23.79

1.6

14.42

2.54

15.33

1.35

10 13.13

1.23

35.95

1.73

36.78

2.32

31.68

2.28

51.13

2.07

50.37

2.63

36.64

1.62

35.11

3.05

39.00

2.79

31.67

0.85

37.54

1.65

15 18.79

3.65

48.19

3.81

45.97

3.78

46.89

1.1

59.65

4.1

58.81

2.56

51.55

3.65

51.93

2.56

48.12

4.03

45.97

3.72

54.21

2.95

20 24.07

2.54

55.42

1.44

53.42

1.53

53.19

2.12

65.06

2.01

62.77

3.51

55.12

1.56

57.33

0.84

55.42

1.4

52.04

2.55

62.96

0.96

30 26.62

3.51

85.30

2.63

74.15

1.67

76.89

3.4

86.56

3.4

72.98

1.95

63.49

2.95

80.73

1.23

80.88

3.0

73.84

0.14

85.15

1.05

40 30.31

0.11

85.55

2.22

79.57

2.8

82.63

3.32

88.03

3.78

79.77

3.41

74.85

3.33

85.24

2.96

84.63

3.57

77.12

2.56

89.67

2.11

50 34.69

0.95

86.41

1.63

89.42

1.33

90.80

1.31

90.87

2.31

87.34

0.97

85.15

1.86

85.95

2.86

85.94

1.42

81.78

0.95

90.84

0.85

60 37.55

0.84

87.54

0.96

89.62

1.5

91.46

3.86

92.35

1.46

94.37

2.66

95.34

1.92

87.16

0.87

88.29

2.53

89.33

2.12

92.28

2.63




0 20 40 600

20

40

60

80

100

Pure Drug

Batch 01

Batch 02

Batch 03

Batch 04

Batch 05

Batch 06

Batch 07

Batch 08

Batch 09

Check point batch(batch 10)

Time, min.

CP

R

Figure 51: Cumulative percentage release for all factorial batches of

pellets, pure drug and check point batch

Perusal from the above Figure 51, it was shown that, all the batches of

pellets showed more than 85% drug release within one hour where as pure

drug showed only 37.55% drug release within one h. Reduced crystallinity

might be a reason for higher dissolution rate.(126) Check point batch showed

92.28% drug release after one hour.

In vitro dissolution study for the prepared CCA and pure drug was

performed using USP type II apparatus. Dissolution profile given in Figure 52

showed large improvement in the rate of drug release. Agglomerates from

batch T-19 showed more than 85% drug release within 30 min (Table 50).

This might be due to hydrophilic polymer inclusion in the formulation. The



greater porosity of prepared CCA (as shown in SEM photos) was also

responsible for providing greater effective surface area and exposure of a

large surface to the dissolution media.(128) The solvent evaporation during

formation of CCA and attrition with the stirrer might attributed towards greater

porosity in the CCA.

The control batch of CCA could not show much improvement in

dissolution compared to pure drug.

Table 50: Dissolution profile data of Chlorzoxazone, CCA and its dosage

form

Time,

min.


Pure drug Control

batch

Batch

T-19

Tablet prepared from

(500 mg drug)

Pure drug T-19

0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

5 11.59 0.35 13.81 1.37 20.21 0.96 12.91 2.35 34.58 0.89

10 13.13 1.23 18.72 2.56 35.12 2.07 16.51 4.18 60.57 2.56

15 18.79 3.65 22.61 0.98 51.93 4.1 21.89 3.08 75.35 2.28

20 24.07 2.54 29.43 2.64 54.65 2.01 25.12 2.53 87.94 4.79

30 26.62 3.51 34.64 1.59 88.04 3.4 31.95 0.57 91.59 0.51

40 30.31 0.11 44.98 3.22 91.96 3.78 34.56 1.78 93.09 0.69

50 34.69 0.95 47.09 1.02 96.79 2.31 35.75 0.37 96.52 0.99

60 37.55 0.84 51.11 1.21 98.27 2.99 36.71 0.72 98.89 0.74




0 20 40 600

20

40

60

80

100

Pure Drug

T-19 CCA Control batch

Pure drug tablet

T-19 tablet

Time, min.

CP

R

Figure 52: Dissolution profile of Chlorzoxazone, optimized CCA and

dosage form

In case of cogrinding of drug with PEG 4000 (1:3), dissolution profile

was studied every hour while grinding till the constant rate of dissolution

achieved. From the dissolution profile, it was seen that, after 3 h grinding, an

increment in rate of dissolution was almost negligible. Hence, dissolution after

3 h and 6 h were selected for further calculations.

The results are given in following Table 51.



Table 51: Dissolution profile of CHLOR: PEG 4000 at different time

intervals and with 1:3 ratio of drug: polymer

Time,

min.

CHLOR: PEG 4000 (1:3)

CPR ± S.D.*

Chlorzoxazone

Control batch

1 h 2 h 3 h 4 h 5 h 6 h 3 h 6 h

0

0.0

±

0.0

0.0

±

0.0

0.0

±

0.0

0.0

±

0.0

0.0

±

0.0

0.0

±

0.0

0.0

±

0.0

0.0

±

0.0

5

28.81

±

1.4

36.42

±

1.13

33.31

±

2.3

36.85

±

0.67

30.89

±

2.17

31.07

±

3.85

18.61

±

1.21

19.83

±

1.63

10

49.75

±

5.77

46.02

±

1.14

42.9

±

6.41

40.44

±

1.99

39.1

±

0.74

35.05

±

2.61

20.56

±

1.05

21.48

±

2.01

15

55.00

±

5.04

45.32

±

1.83

51.24

±

3.49

47.79

±

0.61

45.85

±

0.51

47.83

±

1.83

23.53

±

2.62

23.94

±

3.21

20

55.00

±

1.83

48.1

±

0.78

53.96

±

5.18

51.5

±

1.58

50.39

±

2.16

51.36

±

1.33

24.47

±

1.35

26.00

±

2.61

30

56.8

±

2.1

52.01

±

0.93

60.85

±

5.51

55.6

±

0.54

56.19

±

2.07

59.69

±

0.83

26.03

±

0.95

28.37

±

1.0

40

61.73

±

3.14

55.4

±

0.62

67.55

±

6.2

62.99

±

0.75

63.1

±

0.58

61.13

±

0.97

31.85

±

0.65

36.23

±

3.42

50

65.3

±

3.8

57.43

±

0.67

79.77

±

3.61

71.95

±

0.33

72.94

±

2.02

76.02

±

0.27

39.31

±

1.21

39.83

±

0.98

60

62.42

±

3.09

58.09

±

0.08

87.15

±

2.59

78.01

±

0.9

81.57

±

1.18

84.9

±

0.86

42.00

±

0.77

43.23

±

0.73

70

64.56

±

3.04

58.58

±

0.05

91.99

±

1.43

85.12

±

0.86

86.86

±

0.42

86.74

±

0.01

46.22

±

1.23

47.55

±

0.33

80

64.19

±

0.92

57.04

±

1.16

92.06

±

1.55

88.69

±

0.74

86.68

±

1.02

88.24

±

0.37

49.67

±

1.04

51.22

±

0.65

90

64.06

±

0.78

57.74

±

0.54

90.9

±

1.28

89.98

±

0.64

87.38

±

1.23

88.88

±

1.09

53.18

±

1.08

54.59

±

0.53

* Values are mean of 3 observation (n=3), and values in parenthesis are

standard deviation (± SD)



0 20 40 60 800

20

40

60

80

100

Pure drug 1 hr 2 hr 3 hr 4 hr

5 hr 6 hr Control batch 3 hr Control batch 6 hr

Time, min.

CP

R

Figure 53: Comparative In-vitro drug release profile at different time

intervals of pure drug, control batch and coground sample

The above Figure 53 indicat that, dissolution rate was enhanced to

90% within an hour from the sample collected after 3 h grinding with PEG

4000. Further grinding did not increase the rate of drug dissolution, hence,

grinding of drug with PEG 4000 for 3 h was considered the best sample for

formulation as it also showed good physico-mechanical properties.



Table 52: Dissolution profile of pure drug, ground mixture (1:3) after 3 h

and its dosage form

Time,

min.


Pure drug

Physical

mixture

(1:3 ratio)

Grinding for

3 h

Tablet prepared from

(125 mg drug)

Pure drug Grinding for

3 h

0 0.0 0.0 0.0 0.0 0.0 ± 0.0 0.0 ± 0.0 0.0 0.0

5 11.59 0.35 12.36 0.45 33.31 ± 2.3 10.29 ± 0.21 26.85 ± 0.35

10 13.13 1.23 14.20 0.96 42.9 ± 6.41 11.15 ± 0.52 55.86 ± 1.23

15 18.79 3.65 19.48 3.55 51.24 ± 3.49 14.44 ± 1.25 70.87 ± 3.65

20 24.07 2.54 29.49 1.54 53.96 ± 5.18 16.13 ± 1.04 82.09 ± 2.54

30 26.62 3.51 32.27 3.75 60.85 ± 5.51 21.79 ± 0.15 86.60 ± 3.51

40 30.31 0.11 36.65 2.11 67.55 ± 6.2 24.41 ± 0.56 91.58 ± 0.11

50 34.69 0.95 39.13 1.55 79.77 ± 3.61 30.46 ± 1.06 93.36 ± 0.95

60 37.55 0.84 45.20 1.84 87.15 ± 2.59 32.25 ± 1.03 93.77 ± 0.84


The above Table 52 suggest that, tablets prepared from coground

mixture also showed more than 90% drug release within one hour. Whereas,

tablets prepared from pure drug showed only 32% drug release at the end of

one hour. Moreover, physical mixture of drug and PEG 4000 showed only

45% drug release after one hour. It indicated that, drug was influenced by

cogrinding with polymer and converted into amorphous form, which resulted in

a higher release rate.(129)



In the Figure 54, a comparison of dissolution profile of pure drug,

coground sample for 3 h, physical mixture and their dosage forms is

presented.

0 20 40 600

20

40

60

80

100

Pure drug Physical mixture (1:3) Coground mixture (1:3)

Tab - pure drug Tab. - coground mixture (1:3)

Time, min.

CP

R

Figure 54: Dissolution profiles of Chlorzoxazone, physical mixture of

drug: PEG 4000, coground mixture and dosage forms

4.3.11.2 Dissolution parameters study of pellets, CCA and coground

samples and dosage forms of Chlorzoxazone

Dissolution parameters such as dissolution percent (DP5 min),

dissolution efficiency (%DE10) and time to release 50% of the drug (t50%)

were calculated using equations described in section 4.2.7.2. The results are

given in Table 53.



Table 53: Value of %DE10, DP5 min and t50 for samples as well as

formulation

%DE10 DP5 min, % t50, min

Sample P T P T P T

Pure Drug 8.76 9.71a

and

34.10b

11.00 13.6 --- ---

Pellets

(Batch 10)

28.41 --- 22.67 --- 10.00 ---

CCA

(T-19)

18.89 32.17 20.00 30.53 14.12 7.31

Coground

mixture (1:3)

after 3 h

grinding

35.71 34.10 33.31 26.85 14.00 9.00

P – indicates powder dissolution, T – indicates tablet dissolution.

a indicates for 500 mg and b indicates for 125 mg of tablets

The above results shows that, highest %DE10min was given by

coground mixture, which was an indication of higher amorphization of drug.(67)

4.3.11.3 Statistical analysis of the dissolution profiles of Chlorzoxazone

samples and its formulations(61)

Similarity factor (f2) and mean dissolution time (MDT) were calculated

for the comparison of dissolution profiles of prepared samples with pure

Chlorzoxazone and control batch as per the equations mentioned in section

4.2.8.3. The values are shown in Table 54.



Table 54: Value of f2 and MDT for samples as well as formulation

f2 MDT, min.

Sample Sample Tablet Sample Tablet

Pure Drug -- -- 19.93

13.35 (500 mg) and

21.85 (125 mg)

Pellets (Batch 10) 20.58* --- 13.62 ---

CCA (T-19) 20.77* 18.15* 17.12 11.29

Coground mixture (1:3)

after 3 h grinding 26.59* 16.49* 3.62 11.16

* - indicates dissimilarity between dissolution profiles

The result in MDT indicates the increased dissolution rate of prepared

samples and its formulations than pure drug.(61)

4.3.12 STABILITY STUDY OF CCA, COGROUND SAMPLES

AND DOSAGE FORMS OF CHLORZOXAZONE

Stability study of prepared CCA and coground mixture as well as their

dosage forms was done as per the procedure described in section 4.2.8.

The amount of Chlorzoxazone in the CCA as well as coground mixture

was found 94.03 ± 0.21 mg and 23.92 ± 0.38 mg, respectively after the

storage. The reduction in drug content was very negligible (0.09 and 1.27%,

respectively).

The dissolution profiles of CCA and coground mixture after stability

study (Figure 55 and 56) was also similar compared to samples soon after the

preparation. The statistical analysis also proved sameness in dissolution

profile (f2=74.902 and 67.99, respectively).

The dissolution profiles (Figure 55 and 56) of prepared dosage forms

after stability study in case of CCA and coground mixture were similar to that

of the dosage forms immediately after preparation. The statistical analysis of

dosage form dissolution profiles of CCA and coground mixture after stability



study also proved sameness (f2=84.28 and 88.16, respectively) with their

respective dosage forms before stability study.

Figure 55: Dissolution profiles of batch T-19 and its formulation before

and after stability testing

Figure 56: Dissolution profiles of coground sample and its formulation

before and after stability testing

FTIR Analysis



Figure 57: FT-IR study (CCA) for stability after 3 months of storage at 40

°C/ 75% RH

From the Figure 57 and 58, it is observed that there is no significant

difference in the FT-IR spectra before and after stability study of CCA as well

as coground mixture, respectively. Thus, it is confirmed that no physical and

chemical interaction occurred during the stability study in the samples.

Figure 58: FT-IR study (coground mixture) for stability after 3 months of

storage at 40 °C/ 75% RH

DSC spectra

DSC spectra of CCA and coground mixture further proved that, there

was no interaction occurred between drug and polymers during stability

periods. Figure 59 shows DSC spectra before and after stability study of CCA.



Figure 59: DSC spectra of CCA for stability after 3 months of storage at

40 °C/ 75% RH

Figure 60 below is the comparison of DSC of coground mixture before

and after stability study.

Figure 60: DSC Spectra of Co-ground mixture before and after stability

testing after 3 months of storage at 40 °C/ 75% RH

From the above findings for CCA (Batch 19) and coground mixture of

drug: PEG 4000 (1:3, % w/w), it was suggested that, drug was in a stable

form into the prepared samples as well as dosage forms too.



4.4 BIBLIOGRAPHY

1. Patel RP, Dave BS, Amin AF, Patel MM, Patel JK, Patel JR, Patel SR.

(2005). Modeling and comparison of dissolution profiles of commercial

Metformin HCL sustained release tablets. Drug Del Tech, 5. Available

through electronic version.

2. Raval MK, Bagda AA, Patel JM, Paun JS, Chaudhari KR, Sheth NR.

(2010). Preparation and evaluation of sustained release nimesulide

microspheres using response surface methodology. J Pharm Res, 3 581-

586.

3. Zhang GZ, Zhou D. (2009). In Developing Solid Oral Dosage Forms:

Pharmaceutical Theory and Practice. Burlington: Academic Press, pp 1-

403.

4. Shan N, Zaworotko MJ. (2008). The role of cocrystals in pharmaceutical

science. Drug Discovery Today, 13, 440–446.

5. Gao Y. (2010). Pharmaceutical cocrystals. ChemProg, 22, 829–836.

6. Fleischman SG, Kuduva SS, McMahon JA, Moulton B, Walsh RDB,

Rodriguez-Hornedo N, Zaworotko MJ. (2003). Crystal engineering of the

composition of pharmaceutical phases: multiple component crystalline

solids involving carbamazepine. Cryst Growth Des, 3, 909-919.

7. Hickey MB. (2007). Performance comparison of a co-crystal of

carbamazepine with marketed product. Eur J Pharm Biopharm, 67, 112–

119.

8. Rodriguez-Hornedo N. (2007) Cocrystals: Design, Properties, and

Formation Mechanisms. Encyclopedia of Pharmaceutical Technology,

New York: Informa Healthcare, USA, pp. 615–635.

9. Ibrahim AY, Forbes RT, Blagden N. (2011). Spontaneous crystal growth

of co-crystals: the contribution of particle size reduction and convection

mixing of the co-formers. Cryst Eng Commun, 13, 1141-1152. 10. Blagden N, Matas M, Gavan PT, York P. (2007). Crystal engineering of

active pharmaceutical ingredients to improve solubility and dissolution

rates. Adv Drug Delivery Rev, 59, 617-630.



11. Elchidana PA, Deshpande SG. (1999). Microporous membrane drug

delivery system for indomethacin. J Controlled Release, 59, 279-285.

12. Chatlapalli R, Rohera BD. (1998). Physical characterization of HPMC

and HEC and investigation of their use as pelletization aids. Int J Pharm,

161, 179-193.

13. Prabakaran L, Prushothaman M, Sriganesan P. (2009). Pharmaceutical

micropellets: an overview, Pharmainfo.net, 7(4).

14. Harris MR, Sellassie IG. Formulation Variables. In: Pharmaceutical

Pelletization Technology, New York, Marcel Dekker Inc., 1989, pp 218.

15. Gupta BK, Pal R, Chakraborty M, Debnath R. (2009). Design, evaluation

and optimization of microcapsules of leflunomide with eudragit® RL100

and eudragit® RS100 by solvent evaporation technique. Asian J Pharm,

3, 309-313.

16. Pawar AP, Paradkar AR, Kadam SS, Mahadik KR. (2004a).

Agglomeration of ibuprofen with talc by novel crystallo-co-agglomeration

technique. AAPSPharmSciTech, 5, 30-35.

17. Pawar AP, Paradkar AR, Kadam SS, Mahadik KR. (2004b). Crystallo-co-

agglomeration: a novel process to obtain ibuprofen-paracetamol

agglomerates. AAPS PharmSciTech, 5, 57-64.

18. Maghsoodi M, Taghizadeh O, Martin GP, Nokhodchi A. (2008). Particle

design of naproxen-disintegrant agglomerates for direct compression by

a crystallo-co-agglomeration technique. Int J Pharm, 351, 45–54.

19. Jadhav NR. (1998). Studies on agglomerates of bromhexine

hydrochloride loaded talc prepared by crystallo-co-agglomeration

[master’s thesis], University of Pune.

20. Kale VV, Gadekar S, Ittadwar AM. (2011). Particle size enlargement:

making and understanding of the behavior of powder (particle) system.

Systematic Reviews in Pharmacy, 2, 79-85.

21. Kadam SS, Mahadik KR, Paradkar AR. (1997). A process for making

agglomerates for use as or in a drug delivery system. Indian Patent

183036.



22. Nokhodchi A, Maghsoodi M, Hassan-zadeh D, Barzegar-Jalali M. (2007).

Preparation of agglomerated crystals for improving flowability and

compactibility of poorly flowable and compactable drugs and excipients.

Powder Technol, 175, 73–81.

23. Jadhav NR, Pawar AP, Paradkar AR. (2007). Design and evaluation of

deformable talc agglomerates prepared by crystallo-co-agglomeration

technique for generating heterogenous matrix. AAPS PharmSciTech, 8,

E61-E67.

24. Dinh LQ, Van LN. (2008). Formulation of rapid-released tablets

containing paracetamol and ibuprofen. Tap Chi Duoc Hoc, 48, 10-13.

25. Muatlik S, Usha AN, Reddy MS, Ranjith AK, Pandey S. (2007). Improved

bioavailability of aceclofenac from spherical agglomerates: development,

in vitro and preclinical studies. Pak J Pharm Sci, 20, 218-226.

26. Patterson JE, James MB, Forster AH, Lancaster RW, Butler JM, Rades

T. (2007). Preparation of glass solutions of three poorly water soluble

drugs by spray drying, melt extrusion and ball milling. Int J Pharm, 336,

22–34.

27. Subrahmanyam CVS. (2010). Essentials of Physical Pharmacy. 1st Edn.,

Vallabh Prakashan, New Delhi, pp. 127.

28. Choil WS, Kwak SS, Kim HI. (2006). Improvement of bioavailability of

water insoluble drugs: potential of nano-sized grinding technique. Asian J

Pharm Sci, 1, 27-30.

29. Yamamoto K, Nakano M, Arita T, Nakai Y. (1974). Dissolution rate and

bioavailability of griseofulvin a ground mixture with microcrystalline

cellulose. J Pharmacokinet Biopharm, 2, 487-493.

30. Morita M, Nakai Y, Fukuoka E, Nakajima S. (1984). Physicochemical

properties of crystalline lactose. II. Effect of crystallinity on mechanical

and structural properties. Chem Pharm Bull, 32, 4076-4083.

31. Pirttimaki J, laine E, Ketolainen J, Paranen P. (1993). Effect of grinding

and compression on crystal structure of anhydrous caffeine. Int J Pharm,

95, 93-99.



32. Piyarom S, Yonemochi E, Oguchi T, Yamamoto K. (1997). Effect of

grinding and humidification on transformation of conglomerate to recemic

compound in optically active compounds. J Pharm Pharmcol, 49, 384-

389.

33. Friedrich H, Nada A, Bodmeier R. (2005). Solid state and dissolution rate

characterization of co-ground mixtures of nifedipine and hydrophilic

carriers. Drug Dev Ind Pharm, 31, 719–728.

34. Matsumoto T, Zografi G. (1999). Physical properties of solid molecular

dispersions of indomethacin with poly (vinylpyrrolidone) and poly(vinyl

pyrrolidone-co-vinyl-acetate) in relation to indomethacin crystallization.

Pharm Res,16, 1722–1728.

35. Vadher AM, Parikh JR, Parikh RH, Solanki AB. (2009). Preparation and

characterization of co-grinded mixtures of aceclofenac and neusilin US2

for dissolution enhancement of aceclofenac. AAPS PharmSciTech, 10,

606-614.

36. Zhang L, Chai G, Zeng X, He H, Xu H, Tang X. (2010). Preparation of

fenofibrate immediate-release tablets involving wet grinding for improved

bioavailability. Drug Dev Ind Pharm, 36, 1054–1063.

37. Basalious EB, Shawky N, Badr-Eldin SM. (2010). SNEDDS containing

bioenhancers for improvement of dissolution and oral absorption of

lacidipine. I: development and optimization. Int J Pharm, 391, 203–211.

38. Aulton’s ME. (2007). Pharmaceutics: the design and manufacture of

medicines. 3rd Edn., Churchill Livingstone, London, 13, p176.

39. Vela MT, Fernandes AM, Rabasco AM. (1990). Rheological study of

lactose coated with acrylic resins. Drug Dev Ind Pharm, 16, 295-300.

40. Lachman L, Libermann HA, Kanig JL. (1991). The Theory and Practice

of Industrial Pharmacy, 3rd Edn., Varghese Publishing House, Bombay,

480-481.

41. Martin A, Swarbrick J, Cammarata A. (1991). Physical Pharmacy:

Physical Chemical Principles in The Pharmaceutical Sciences. 3rd Edn,

Varghese Publishing House, Bombay, pp. 447-448.



42. Kawashima Y. (1984). Development of spherical crystallization technique

and its application to pharmaceutical systems. Arch Pharm Res, 7, 145-

151.

43. Ueda M, Nakamura Y, Makita H, Imasato Y, Kawashima Y. (1991).

Particle design of enoxacin by spherical crystallization technique II,

characteristics of agglomerated crystals, Chem Pharm Bull, 39, 1277-

1281.

44. Denny P. (2002). Compaction equations: a comparison of the heckel and

kawakita equations. Powder Technol, 127, 162–172.

45. Kawakita K, Ludde KH. (1970). Some considerations on powder

equations. Powder Technol, 4, 61–68.

46. Chavda V, Maheshwari RK. (2008). Tailoring of ketoprofen particle

morphology via novel crystallo-co-agglomeration technique to obtain a

directly compressible material. Asian J Pharm, 2, 61-67.

47. Patra N, Singh SP, HamdP, Vimladevi M. (2007). A sysyematic study on

micromeritic properties and consolidation behavior of the terminaliya

arjuna bark powder for processing into tablet dosage from. Int J Pharma

Excip, 6, 6-7.

48. Chaulang G, Patil K, Ghodke D, Khan S. (2008). Preparation and

characterization of solid dispersion tablet of furosemide with

crospovidone. Research J Pharm Technol, 1, 386-389.

49. Brittain G. (2001). Particle size distribution, representations of particle

shape, size, and distribution. Pharm Technol, 38–45.

50. Kumar S, Chawla G, Bansal AK. (2008). Role of additives like polymers

and surfactants in the crystallization of mebendazole. Yakugaku Zasshi,

128, 281-289.

51. Banga S, Chawla G, Varandani D, Mehta BR, Bansal AK. (2007).

Modification of the crystal habit of celecoxib for improved processibility. J

Pharm Pharmcol, 59, 1-11.

52. Pawar AP. (1999). Studies on spherical crystallization of various

pharmaceuticals [doctoral thesis]. University of Pune.



53. Jarosz PJ, Parrot EJ. (1983). Comparison of granule strength and tablet

strength. J Pharm Sci, 72, 530-535.

54. Heckel RW. (1961). An analysis of powder compaction phenomena.

Trans Metall Soc. AIME, 221, 671–675.

55. Rundick A, Hunter AR, Holden FC. (1963). An analysis of the diametral

compression test. Mater Res Stand, 3, 283–289.

56. Armstrong NA, Haines-Nutt RF. (1974). Elastic recovery and surface

area changes in compacted powder systems. Powder Technol, 9, 287-

290.

57. Armstrong NA, Palfrey LP. (1989). The Effect of machine speed on the

consolidation of four directly compressible tablet diluents. J Pharm

Pharmcol, 41,149-151.

58. Gohel MC, Jogani PD. (1999). An Investigation of the direct compression

characteristics of co processed lactose microcrystalline cellulose using

statistical design. Pharm Technol, 23, 54-62.

59. Shivakumar HG, Ramalingaraju G. (1999). Influence of solvents on

crystal habit and properties of paracetamol crystals, Ind J Pharm Sci, 61,

100-104.

60. Vyazovkin S. (2008). Thermal analysis. Anal Chem, 80, 4301–4316.

61. Patel R, Bhimani D, Patel J, Patel D. (2008). Solid-state characterization

and dissolution properties of ezetimibe–cyclodextrins inclusion

complexes. J Incl Phenom Macrocyclic Chem, 60, 241–251.

62. Maghsoodi M, Hassan-Zadeh D, Barzegar-Jalali M. (2007). Improved

compaction and packing properties of naproxen agglomerated crystals

obtained by spherical crystallization technique. Drug Dev Ind Pharma,

33, 1216–1224,

63. Bandyopadhyay R, Selbo J, Amidon GE, Hawley M. (2005). Application

of powder x-ray diffraction in studying the compaction behavior of bulk

pharmaceutical powders. J Pharm Sci, 94, 2520-2530.

64. Hector NA, Anailien BR, Rolando GH, Dulce MCE, Marilo VL. (2000).

Physico-chemical and solid-state characterization of secnidazole. Il

Farmaco, 55, 700–707.



65. Mallick S. (2004). Effect of solvent and polymer additives on

crystallization. Indian J Pharm Sci, 66, 142-147.

66. United States Pharmacopoeia 29 / NF-24. (2006). United States

Pharmacopoeial Convention Inc, pp. 576.

67. Dahiya S. (2010). Studies on formulation development of a poorly water-

soluble drug through solid dispersion technique. Thai J Pharm Sci, 34,

77-87.

68. Anderson NH, Bauer M, Boussac N, Khan-Malek R, Munden P, Sardaro

M. (1998). An evaluation of fit factors and dissolution efficiency for the

comparison of in vitro dissolution profiles. J Pharm Biomed Anal, 17,

811–822.

69. Moore JW, Flanner HH. (1996). Mathematical comparison of curves with

an emphasis on in vitro dissolution profiles. Pharm Technol, 20, 64-74.

70. Paradkar AR, Pawar AP, Jadhav NR. (2010). Crystallo-co-

agglomeration: a novel particle engineering technique. Asian J Pharma,

4, 4-10.

71. Kachrimanis K, Ktistis G, Malamataris S. (1998). Crystallization

conditions and physico-mechanical properties of ibuprofen–eudragit

S100 spherical crystal agglomerates prepared by the solvent-change

technique. Int J Pharm, 173, 61–74.

72. Markmana O, Roha C, Robertsa MF, Martha MT. (1996). Designed

additives for controlled growth of crystals of phospholipid interacting

proteins: Short chain phospholipids. J Cryst Growth, 160, 382-388.

73. Raghavan SL, Trividic A, Davis AF, Hadgraft J. (2001). Crystallization of

hydrocortisone acetate: influence of polymers. Int J Pharm, 212, 213–

221.

74. Black SN, Davey RJ, Halcrow M. (1986). The kinetics of crystal growth in

the presence of tailor-made additives. J Cryst Growth, 79, 765-774.

75. Otsuka M, Matsuda Y. (1995). Polymorphism, Pharmaceutical Aspects.

Encyclopedia of Pharmaceutical Technology. New York, Marcel Dekker,

pp. 305–326.



76. Schultheiss N, Newman A. (2009). Pharmaceutical cocrystals and their

physicochemical properties. Cryst Growth Des, 9, 2950–2967.

77. Yuan G, Hui Z, Jianjun Z. (2011). Enhanced dissolution and stability of

adefovir dipivoxil by cocrystal formation. J Pharm Pharmacol, 63, 483-

490.

78. Parmar VK. (2010). Studies of physicochemical properties of active

pharmaceutical ingredient and its modification for improvement of its

functionality. [Master’s thesis], The Gujarat University.

79. Raval MK, Sorathiya KR, Chauhan NP, Patel JM, Parikh RK, Sheth NR.

(2012). Influence of polymers/excipients on development of

agglomerated crystals of secnidazole by crystallo-co-agglomeration

technique to improve processability. Drug Dev Ind Pharm, Electronic

version, March 2’ 2012, doi: 10.3109/03639045.2012.662508.

80. Barot BS, Parejiya PB, Patel TM, Parikh RK, Gohel MC. (2010).

Development of directly compressible Metformin hydrochloride by the

spray-drying technique. Acta Pharm, 60,165–175.

81. Kawashima Y, Imai M, Takeuchi H, Yamamoto H, Kamiya K, Hino T.

(2003). Improved flowability and compactibility of spherically

agglomerated crystals of ascorbic acid for direct tableting designed by

spherical crystallization process. Powder Technol, 130, 283-289.

82. Kawashima Y, Takenaka H, Okumura M, Kojma K. (1984). Direct

preparation of spherically agglomerated Salicylic acid crystals using

crystallization. J Pharm Sci, 73, 1534-1538.

83. Paroren P, Juslin M. (1983). Compressional characteristics of four

starches. J Pharm Pharmacol, 35, 627-635.

84. Joshi A, Shah SP, Misra AP. (2003). Preparation and evaluation of

directly compressible forms of rifampicin and ibuprofen. Ind J Pharm Sci,

65, 232-238.

85. Monajjemzadeh F, Hassanzadeh D, Valizadeh H, Siahi-Shadbad MR,

Mojarrad JS, Robertson TA, Roberts MS. (2009). Compatibility studies of

acyclovir and lactose in physical mixtures and commercial tablets.

Eur J Pharm Biopharm, 73, 404-413.



86. Patil SA, Kuchekar BS, Chabukswar AR, Jagdale SC. (2010).

Formulation and evaluation of extended-release solid dispersion of

Metformin Hydrochloride. J Young Pharm, 2, 121–129.

87. Gao Y, Zu H, Zhang J. (2011). Enhanced dissolution and stability of

adefovir dipivoxil by cocrystal formation. J Pharm Pharmacol, 63, 483-

490.

88. Shah PP, Mashru RC. (2008). Development and evaluation of

artemether taste masked rapid disintegrating tablets with improved

dissolution using solid dispersion technique. AAPS PharmSciTech, 9,

494-500.

89. Tiwari AK. (2001). Modification of crystal habit and its role in dosage

form performance. Drug Dev Ind Pharm, 27, 699-709.

90. Kaialy W, Larhrib H, Martin GP, Nokhodchi A. (2012). The Effect of Engineered

mannitol-lactose mixture on dry powder inhaler performance. Pharm Res,

Electronic version.

91. Subrahmanyam CVS. (2010). Textbook of Biopharmaceutics and

Pharmacokinetics. 1st Edn., Vallabh Prakashan, New Delhi, pp. 37.

92. Brittain HG. (1999). Polymorphism in Pharmaceutical Solids. Vol. 95.

New York, Marcel Dekker, pp. 227–278.

93. Sarkar M, Perumal OP, Panchagnula R. (2008). Solid-state

characterization of Nevirapine. Ind J Pharm Sci, 70, 619-630.

94. Sekikawa H, Nakano M, Arita T. (1978). Inhibitory effect of polyvinyl

pyrollidone on the crystallization of drugs, Chem Pharm Bull, 26, 118-

126.

95. Ribardiere P, Tchoreloff G, Puisieux F. (1996). Modification of ketoprofen

bead structure produced by the spherical crystallization technique with a

two-solvent system, Int J Pharm, 144, 195-207.

96. Ring TA. (1991). Kinetic effects on particle morphology and size

distribution during batch precipitation. Powder Technol, 95, 195-206.

97. Nocent M, Bertocchi L, Espitalier F, Baron M, Couarraze G. (2001).

Defination of a solvent system for spherical crystallization of salbutamol



sulfate by quasi-emulsion solvent diffusion (QESD) method. J Pharm Sci,

90, 1620-1627.

98. Willart JF, Descamps M. (2008). Solid state amorphization of

pharmaceuticals. Mol Pharmaceutics. 5, 905-920.

99. Yamashita K, Nakate T, Okimoto K, Ohike A, Tokunaga Y, Ibuki R,

Higaki K, Kimura T. (2003). Establishment of new preparation method for

solid dispersion formulation of tacrolimus. Int J Pharm, 267, 79–91.

100. Kawakita, K. (1956). Compression of powder. Kagaku, 26, 149–150.

101. Kuno H, in: G. Jimbo, et al. (Ed.), Funtai (Powder theory and

application), Maruzen, Tokyo, 1979, p 342.

102. Lin CW, Chain TM. (1995). Compression behavior and tensile strength of

heat-treated polyethylene glycols. Int J Pharm, 118, 169-179.

103. Rodriguez L, Cavallari C, Passerini N, Albertini B, Gonzalez-Rodriguez

ML, Fini A. (2002). Preparation and characterization by morphological

analysis of diclofenac/ PEG 4000 granules obtained using three different

techniques. Int J Pharm, 242, 285–289.

104. Bartsch SE, Griesser UJ. (2004). Physicochemical properties of the

binary system glibenclamide and polyethylene glycol 4000. J Therm Anal

Calorim, 77, 555–569.

105. Yadav VB, Yadav AV. (2009). Polymeric recrystallized agglomerates of

cefuroxime axetil prepared by emulsion solvent diffusion technique.

Tropical J Pharm Res, 8, 361-369.

106. Pawar AP, Paradkar AR, Kadam SS, Mahadik KR. (2007) Effect of

polymers on crystallo-co-agglomeration of Ibuprofen-Paracetamol:

factorial design. J Pharm Sci, 69, 658-664.

107. Mashru RC, Sutariya VB, Sankalia MG, Parikh PP. (2005). Development

and evaluation of fast-dissolving film of salbutamol sulphate. Drug Dev

Ind Pharm, 31, 25–34.

108. Derringer G, Suich R. (1980). Simultaneous optimization of several

responses variables. J Quality Technol, 12, 214–219.



109. Gohel MC, Amin AF. (1998). Formulation optimization of controlled

release diclofenac sodium microspheres using factorial design, J

Controlled Release, 51, 115–122.

110. Gohel MC, Panchal MK. (2002). Novel use of similarity factor f2 and Sd

for the development of diltiazem HCl modified-release tablets using a 32

factorial design. Drug Dev Ind Pharm, 28, 77–87.

111. Shah TJ, Amin AF, Parikh JR, Parikh RH. (2007). Process optimization

and characterization of poloxamer solid dispersions of a poorly water-

soluble Drug, AAPS Pharm SciTech, 8, 29, E1- E7.

112. Nighute AB, Bhise SB. (2009). Preparation and evaluation of rifabutin

loaded polymeric microspheres, Res J Pharm Tech, 2, 371-374.

113. Mahmoodi F, Alderborn G, Frenning G. (2010). Effect of lubrication on

the distribution of force between spherical agglomerates during

compression, Powder Technol, 198, 69 –74.

114. Garg R, Gupta GD. (2010). Gastro retentive floating microspheres of

Silymarin: preparation and In vitro evaluation. Tropical J Pharm Res, 9,

59-66.

115. Kibria G, Jalil R. (2007). In vitro release kinetics study of diltiazem

hydrochloride from pellets using an ethyl cellulose pseudo latex coating

system, J Pharm Sci, 6, 87-92.

116. Palanisamy M, Khanam J. (2011). Cellulose-based matrix microspheres

of prednisolone inclusion complex: preparation and characterization.

AAPS PharmSciTech, 12, 388-400.

117. Das MK, Rao KR. (2007). Microencapsulation of zidovudine by double

emulsion solvent diffusion technique using ethyl cellulose. Ind J Pharm

Sci, 69, 244-250.

118. Tayade PT, Kale RD. (2004). Encapsulation of water-insoluble drug by a

cross-linking technique: effect of process and formulation variables on

encapsulation efficiency, particle size, and In vitro dissolution rate. AAPS

PharmSciTech, 6, 112-119.

119. Modi A, Tayade P. (2005). Enhancement of dissolution profile by solid

dispersion (kneading) technique. AAPS PharmSciTech, 7, E1-E6.



120. Yoshihashi Y, Kitano H, Yonemochi E, Terada K. (2000). Quantitative

correlation between initial dissolution rate and heat of fusion of drug

substance. Int J Pharm, 204, 1-6.

121. Chandak AR, Verma PRP. (2008). Design and development of HPMC

based polymeric film of methotrexate-physicochemical and

pharmacokinetic evaluation. Yakugaku zasshi, 128, 1057-1066.

122. Bonet M, Quijada C, Cases F. (2004). Characterization of ethyl cellulose

with different degrees of substitution: a diffuse-reflectance infrared study.

Can J Anal Sci Spectros, 49, 234-239.

123. Jbilou M, Ettabia A, Guyot-Hermann A, Guyot JC. (1999). Ibuprofen

agglomerates preparation by phase separation. Drug Dev Ind Pharm, 25,

297–305.

124. Gupta VR, Mutalik S, Patel MM, Jani GK. (2007). Spherical crystals of

celecoxib to improve solubility, dissolution rate and micromeritic

properties. Acta Pharm, 57, 173–184.

125. Wang Q, Sanming Li, Che X, Fan X, Chaojie Li. (2010). Dissolution

improvement and stabilization of ibuprofen by co-grinding in a β-

cyclodextrin ground complex. Asian J Pharm Sci, 5, 188-193.

126. Bhole PG, Patil VR. (2009). Enhancement of water solubility of felodipine

by preparing solid dispersion using poly-ethylene glycol 6000 and poly-

alcohol. Asian J Pharm, 3, 240-244.

127. Lachman L, Liberman HA, Kanig JL. (1976) Theory and Practice of

Industrial Pharmacy. 2nd edn., Philadelphia, USA, pp. 338-339.

128. Vazquez D, Takagi S, Frukhtbeyn S, Chow LC. (2010). Effects of

addition of mannitol crystallization the porosity and dissolution rate of a

calcium phosphate cement. J Res Natl Inst Stand Technol, 115, 225-

232.

129. Vogt M, Kunath K, Dressman JB. (2008). Dissolution enhancement of

fenofibrate by micronisation, cogrinding and spray-drying: comparison

with commercial preparations. Eur J Pharm Biopharm, 68, 283–288.

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