Journal of Scientific & Industrial Research Vol.58, September 1999, pp 717-722

Design and Evaluation of An Oral Controlled Release Microparticulate Drug Delivery System of Nimesulide by Ionotropic Gelation Technique

and Statistical Optimization by Factorial Analysis

A Manna, I Ghosh, N Goswami, L K Ghosh and B K Gupta* Division of Pharmaceutics, Biopharmaceutics and Clinical Pharmacokinetics,Department of Pharmaceutical Technology, Jadavpur

Universi ty,_Calcutta 700 032, India

Received: 31 March 1999; accepted: 22 June 1999

An attempt was made to prepare aqueous solvent based mi cropelletization of nimesulide by ionotropic gelation technique, with a view to deliver the drug at sustained manner in the gastro-intes tinal tract and consequently into the systemic circulation. Present method being aqueous solvent based, it eliminates the problems and hazards associated with the organi c solvent. Two types of micropell ets were prepared ; one batch was prepared with sodium alginate and other batches were prepared with sod ium alginate and hydroxypropyl methylcellulose (HPMC) using calCium chloride as counter ion soluti on. Prepared micropellets were spherical and free fl owing. These micropell ets were subjected to different physico-chemical evaluation, dissolution and continuous pH dissolution study, which gave sati sfa~tory results . Micropellets prepared with sodium alginate were capable of sustai ning the ac tion for 5-6 h and those prepared with both sodium alginate and HPMC were capable of sustaining action for 8 h. Finally statistical optimization was done with two-way

analysis of variance (ANOVA) and linear regression analysis.

Introduction

Micropelletization 1-3 has become a common technique in the production of controlled release dosage form s. A great deal of work has been done by the scientists about the current application and future possibility for altering the drug activity and stability by packing them in micropellets . The problems associated with organic so l­vent-based micropelletization procedure (cost, safety and environmental pollution)

Materials and Methods Nimesulide; Sodium Alginate (Lamina ria hyperqoria );

HPMC (Methocel K-15M) of Dow Chemical ; Calcium chloride, dihydrate (Analytical grade, E. Merck , Germany); Potass ium dihydrogen phosphate (E. Merck) . All other re­agents are of analytical grades and used without further

purification .

I Preparation of Micropellets Two sets of micropellets were prepared. In the first set

four batches of micropellet s were prepared (A I ,A2,A3,A4 ) using sodium alginate as the coating poly-

* Author for correspondence

mer. To 50 ml of sodium alginate 2 - 4 per cent (w/v) mu­cilage in distilled water, 500 mg of nimesulide was added and thoroughly mixed in an electric stirrer at 500 rpm . For bead formation , 50 ml of aqueous solution was introduced dropwise from a needle into 100 ml of aqueous calc ium chloride 4 - 6 per cent (w/v) being stirred at 100 rpm . Af­ter addition of last drop to the counter ion solution, it was harvested for 10minutes, the beads were washed with di s­tilled water, and dried at 70°C for 6 h. in an oven. and the advantages of aqueous systems have long been known . There is a tendency in industry to switch from organic coat­ing to aqueous coating.

Nimesulide4 , chemically, 4-nitro- 2- phenoxy methane

sulphonamide, is a relatively new non-steroidal anti-in­fl ammatory analgesic drug. It is widely used for the treat­ment of inflammatory condition associated with rheuma­toid arthritis, respiratory tract infection, soft tissue and oral cavity inflammation. The drug appears to be parti cularly useful for patients having allergic hypersensitivity to aspi­rin and other non-steroidal anti-inflammatory drugs 5.

The objective of the study was to prepare a oral con­trolled delivery of nimesulide for the better management of arthritis and algesia and reduce gastric irritation and ul­ceration. In the present study an attempt was made to pre­pare alginate micropellets of nimesulide by ionotropic

718 J SCI IND RES VOL.58 SEPTEMBER 1999

Table I - Formulation design and physicochemical characteristics of nimesulide micropellets

Batch no. .Sodium Calcium chloride HPMC Drug load (mg) Entrapment LSC TSO alginate

Al SOO

A2 + SOO

A3 + SOO

A4 + + SOO

BI + SOO

B2 + + SOO

B3 + + SOO

84· + + + SOO

Level Sodium alginate HPMC

+ 4 per cent (w/v) 2 per cent (w/v) 2 per cent (w/v) I per cent (w/v)

gelation technique 6. 7. Nimesulide was incorporated into beads by two polymers. In the first phase drug was coated with alginate polymer and in the second phase drug was coated both with alginate and hydroxyl propyl methyl cell u 10se(HPMC) (ref. 8) by reacting sodium alginate in presence of polyvalent cation calcium(Ca+2) in situ. The effect of each polymer and counter ion solution on the re­lease profile and drug entrapment efficiency was investi­gated and other desired physico chemical properties were also investigated. Finally statistical optimization was car­ried out by two-way analysis of variance (ANOVA).

In the second set also four batches of micropellets were prepared (B I,B2,B3 ,B4 ) using coating polymer sodium alginate and HPMC. To 50 ml of distilled water, HPMC I - 2 per cent (w/v) were added and stirred with the electric stirrer unti l it forms mucilage. Then sodium alginate 4 per cent was added to form uniform mucilage. Then finally 500 mg of the drug was added and the fi nal mixture was subjected to bead formation as described earlier. The for­mulation design of the micropellets is given in Table 1.

2 Physico Chemical Properties The micropellets prepared were subjected to various

physico chemical studies to assess different physico chemi­cal properties of interest. These studies included :

(i) Granulometric Study As the particle size is a very significant effect on the

release profile of micropellets , granulometric study was conducted to determine the particle size distribution pat-

Efficiency Per cent Per cent Per cent

73 .432 9.4 3. 11

71.841 8.0 3.SI

81.IS2 6.3 3.79

79.S80 4.9 4.2 1

79.62 4. 1 S.18

78 .07 3.8 5.39

88.12 2.2 6.07

84.69 2.2 5.77

Calcium chloride 6 per cent (w/v) 4 per cent (w/v)

tern. For this study, sieve analysis was carried out us.ing a mechanical sieve, using different meshes ( #12, #16, #20, #30) of American Society of Testing Materials (ASTM). The size distribution of the micropellets is reported in Table 2. (ii) Drug Entrapment Efficiency (DEE)

Accurately weighed 25 mg micropellets of (#16 sieve size) was suspended in 100 ml of Nil 00 of NaOH (pH- I 2) and it was kept for 24 h. Next day it was stirred for 15 min, after filtration and proper dilution nimesulide content in the filtrate was analyzed spectrophotometrically at 394 nm wavelength in Beckman DU 64 spectrophotometer. The results obtained are reported in Table 1.

(iii) Loose Surface Crystal Study (LSC Study) In this study9 accurately weighed 25 mg of micropellets

(# 16) was suspended in the phosphate buffer pH 7.2 and was shaken vigorously for 5 min. The drug leached out from the surface of the micropellets was analyzed at 394 nm wavelength spectrophotometrically. Results are reported in Table I .

(iv) Surface Study This study was done on the micropellets using SEM

Hitachi- S 4 I 5A at the foll owing condition (a) thickness of the gold coating was 200 AO (b) potential applied 25 KV (c) tilt was 0°, (d) working di stance was kept at 15 nm.

(v) Flow Property Angle of repose lO method was employed to assess the

flow ability. Micropellets were allowed to fall freely through

MANNA e/ al.: MICROPARTICULATE DRUG DELIVERY SYSTEM OF NIMESULIDE 719

100 ~Al

90 - -1'.2 ____ A3

80 -D-A4

1 70 -Bl

i 60 --.-82.

I -0-83

so -84

1 40 -Ir- B3(COnI

1 30 ___ ~'i\conl pH)

20

10

0 0 2 10

Tore (H')

Fig I - In-vitro dissolut ion profile of Nimesulide from various batches of micropellets

a funnel fixed at I em above the horizontal flat surface, until the apex of the conical pile just touched the tip of the funnel. The angle of repose (a) was determined by the formula :

a = arctan(H/R); H = Cone height of micropellets; R = /'

Radius of the circultr base formed by the micropellels on the ground.

3 In- Vitro Dissolution Study

In -vitro drug release profi Ie of the micropellets were evaluated using USP XXIII rotating basket dissolution ap­paratus with the basket covered with 100 mesh nylon cloth to prevent escaping of the micropellets. Dissolution fluid was 900 ml of phosphate buffer pH 7.2, maintained at 37 ± 10 C and the basket was rotated at 100 ± 2 rpm. Accu­rately weighed amount of micropellets was placed in the

Figure 2a - SEM photographs of sodium alginate

haskets. At 30 min intervals 10 ml of the aliquots were removed and replaced by same volume of phosphate buffer of pH 7.2. Amount of nimesulide released was assayed spectrophotometrically at 394 nm wavelength. TheT50 per cent release ofnimesu lide from micropellets (Table 2). The continuous pH study I I was also carried out for batch A I and B3 to determine the effect of pH on the drug release profile. The release profile of the drug is shown in Figure 1.

Results and Discussion The micropellets formed by th; ionotropic gelation of

sodi um alginate and calcium ch loride, are sufficiently hard and spherical in shape. Stirring speed and the harvesting time of the feed has significant effect on the bead size and entrapment efficiency of the drug. From the preliminary studies it is observed that with the increase in stirring speed

Table 2 - Size di stribution of the sodium alginate micropellets and the sodium alginate­HPMC micropellets of nimesulide

Batch Per cent weight retained on various sieve size* no.

# 12 (1.68 mm) # 16 (1.19 mm) # 20 (0.84 mm) # 30 (0.59 mm)

A l 18.6 69 .68 8.48 3.24 A2 10.22 79.22 7.37 3.19 A3 14.43 73 .04 10.11 2.42 A4 13.62 74.61 6.86 4.91 B1 19.63 73.99 5.12 1.26 B2 17.53 75.62 4.96 1.89 B3 18.47 71 .35 7.46 2.72 B4 25.18 67 .82 6. 11 0.89

* United States Sieve Series

720 J SCI IND RES VOL.58 SEPTEMBER 1999

Figure 2b- SEM photographs of sodium alginate micropellets before dissolution HPMCmicropellets before disso­lution

Figure 2c - SEM photographs of sodium alginate­HPMC micropellets after dissolution

Hydration starts slowly

011 the surface, and forms

'a gel layer.

CORE Drug depleted swollen gel

Dry pellet 1- 1-- /J~ //'. ---"-" // ""

--(~ 'I \ ' \ -------1~ I \

'II ) , , Ii \ / Dissolution \ / '~ ___ // Completed \"', //

Swollen 1 Layer ~ MedIUm .... -.... ./ (PH==7.2)

(1) HPMC prevent rapid swelling of the interior (2) Drug diffuses through gel layer.

Figure 3 - Hypothesis of the swelling controlled release mechanism of Nimesulide Micropellets in dissolution medium.

of the calcium chloride (counter ion solution) , the bead size is decreased. Also it is found that with the increase in harvesting time, the beads formed in calcium ch loride so­lution in tum decrease the drug entrapment efficiency.

In the granulometric study it is observed from the Table 2 that about 67 to 79 per cent of the micropellets were of 16 mesh size, which proves the flexibility of the method i.e. particle size can easily be controlled by adjusting bore of the needle. It is observed that with the increase in the percentage of sodium alginate, maximum amount of the pellets of desired size is obtained. on the other hand with the increase in HPMC percentage, the distribution of the particle size shifts to the higher sieve size due to increase

in the internal viscosity of the medium .

The loose surface crystal study is an important param­eter by which, the bursting effect of micropellets can be known when it comes in contact with the GI fluid . The percentage LSC (Table 1) in case of sodium alginate micropellets is slightly higher than the sodium alginate HPMC micropellets , which gives an indication of com­paratively rapid bursting of the micropellets prepared from the sodium alginate alone.

In all the batches the angle repose is less than 15°, which indicates that the micropellets, hi ghly free flowing .

The Scanning Electron Microscopy of the micropellets prepared from alone with alginate(Figure 2a) are spheri -

MANNA et al. : MICROPARTICULATE DRUG DELIVERY SYSTEM OF NIMESULIDE 72 1

cal in shape and exhibils uniformity and rough surface as well. However in case sodium alginate -HPMC micropellets (Figure 2b) the sphericity is slightly destroyed due to higher internal viscosity, but uniformity is maintained. Micropellets prepared only with the sodium alginate is not subjected to SEM studies after dissolution because they converted to gel type of matrix when dissolution is over. Sodium algi­nate-HPMC micropellets after dissolution (Figure 2c) in­dicates the presence of pores of unaltered shape, which implies a diffusion controlled release mechanism.

Drug Entrapment Efficiency (DEE) shows that with in­crease in percentage in sodium alginate there is significant effect on the drug efficiency. Increase in percentage of so­dium alginate and HPMC, increase the DEE in the micropellets (Table I) . Amount of calcium chloride has less significant effect on the drug entrapment efficiency.

It is observed from the dissolution study that increase in percentage of sodium alginate offers more sustained effect of the drug (Figure I) . But the sustained effect does not last for more than 6 h. On the contrary sodium alginate­HPMC beads give a sustained release for 8 h or more and the shape of the beads remain unaltered. The batches A I -A4 give a diffusion controlled release mechanism '2 and follows Higuchi type of release kinetics '3 ( correlation co­efficient 0.995,0.989,0.977,0.980 for batch no. A I to A4 respectively) and batches B I-B4 follows zero order kinet­ics (correlation coefficients 0.993,0.991,0.995,0.996 for batch no. B I to B4 respectively). From the in-vitro release study t

50% is evaluated. Finally a high satisfactory results

are obtained in continuos pH dissolution study. It is ob­served that at pH 1-3.5, no release of drug occurs from the pellets and at pH higher than 4, the release of the drug initiates and gives a controlled release pattern for about 8 h in case of HPMC-sodium alginate micropellets. No re­lease of drug occurs from the micropellets prepared with

. alginate alone, when the pH of the medium is 1-2.7. After then release of the drug initiates and increases with the increase of pH. A hypothetical model of the swelling con­trolled release mechanism of nimesulide micropellets in dissolution medium is shown in the Figure 3.

Statistical Optimization Application of statistical design experiments to phar­

maceutical problems has appeared to be extremely useful in recent years . The effect of several factors and their in­teractions can be determined simultaneously by Factorial Design Experiments. The Factorial Design may be useful for screening purpose or an aid in identifying individual effects of complex systems. It offers a good degree of effi­cacy and possibility of detecting interactions between fac­tors. Factor effectiveness can be expressed with a math-

ematical model that explains the influence numerically. The objeclive of this work is to outline 22 Factorial Design and to study the effects of polymers and calcium chloride on the release rate of nimesulide from micropellets. The ideal micropellets were found by evaluating these findings .

Statistical analysis'2.'4. '5 based on the strong mathemati­cal model , was done for studying various effects of pro­cess variables on the dependent variables. In the first study sodium alginate and calcium chloride were fixed as pro­cess variables or independent variables and in the second study HPMC and calcium chloride were taken as process variables. These were fixed at 2 levels : high (+ I), and low (-I) The dependent variable was Higuchi permeation rate constants and drug entrapment efficiency. Statisti­cal analysis was done , by (i) Analysis of Vari ance (ANOVA)'2.'4 and (ii) Linear Regression Models 12 . In the experiment duplicate results were obtained for each com­bination of factors fitting a linear equation, which is of fi~st order polynomial.

In the first study when sodium alginate and calcium chlo­ride were variable factors:

On the drug entrapment efficiency (Y) The effect of sodium alginate is significant, p < 0.01

The effect of calcium chloride is not significant, p > 0.0 I The fitted first order polynomial model obtained by linear regression analysis is: Y

I :;:: 95.55 - 4.48(XI -3) - 1.07(X

2 -5)

XI' X2

are the percentage (w/v) of sodium alginate and calcium chloride.

On the drug release rate_ (Y2

)

The effect of sodium alginate is significant, p < 0.0 I The effect of calcium chloride is significant, p < 0.0 I

The fitted first order polynomial model obtained by lin­ear regression analysis is:

Y2

:;:: 70.237 - 4.325(X, -3) - 1.735(X2 ~5)

XI ,X2

are the percentage (w/v) of sodium alginate and calcium chloride.

In the second study when HPMC and calcium chloride were variable factors;

On the drug entrapment efficiency (>'.1)

The effect of HPMC is significant, p < 0.0 I The effect of calcium chloride is significant, p < 0.0 1

722 J SCI IND RES VOL.58 SEPTEMBER 1999

The fitted first order polynomial model obtained by lin­ear regression analysis is:

Y3 = 102.466 - 7.177 *2 (X3 -1.5) - 1 .39( X2 -5) X

3, X

2 are the percentage in (w/v) of HPMC and

calcium chloride.

On the drug release rate (Y4

)

The effect of HPMC is significant, p < 0.01 The effect of calcium chloride is not

significant , p > 0.0 I .

The fitted first order polynomial model obtained by lin­ear regression analysis is:

Y4 = 48.9225 - 5.145 *2 (Xl -1.5) Xl - 0.7075 (X2 -5)

Xl' X2

are the percentage (w/v) of HPMC and calcium chloride.

keferences

Joseph R, Robinson & Vincent H L Lee, Controlled Drug De­li Fer.\', 2nd ed (Mercel Dekker, New York) 1987, 374-421

2 Liberman H A, Lachman L & Schwart z J B, Bioavailabilit), of Tablet Technology in Phannaceutical Dosage Forms-Tablets Vol 2, 2nd ed (Mercel Dekker, New York) 1990, 394-402.

3 Lachman L, Uebennan H A & .Kanig J K, The Th eory and Practice of Industrial Pharmacy 3rd ed (Varaghese Publishing House) 199 I, 243··290

4 Kapoor A, Majumdar 0 K & Yadav M R, indian J Chern 37B ( 1998), 572-575.

5 Tripathy K 0, Essentials of Medical Pharmacology, 3rd ed (Jaypee Brothers Medical Publishers Printers Limited) 1994, 410-429 .

6 Lim.L Y, Wan Lucy S C & Thai P Y, Drug Dev Ind Pharm, 23(10) (1997) 98 I -985

7 Lim L Y & Wan Lucy S C, Drug Dev Ind Pharm , 23(10) (1997) 973-980.

8 Handbook of Pharmaceutical Excipiellts (American Pharma­ceutical Association and Pharmaceutical Society, Great Brit­ain) 138-140,257··258

9 Abu- Izza Khaw la, Garcia-Contreras Lucil a & Robert Lu 0 , J Phanna Sc, 85 (No.6) (1996), 575-576.

10 Martin Alfred, Physical Pharmacy, 4th edn (B I Waverly Pvt Ltd, Delhi) 1995,330-337,423-448.

II Das Sudip, In vito Dissolulion Profile of Theophylline Loaded Ethyl Cellulose Microspheres prepared by Emul sifi cation Sol­vent Evaporation Drug Dev Ind PhQ/m , 17 (18) (1991) 2521-2528.

12 Ozyazici M, Sevgi F & Ertan G, Drug Dev Ind Pharm, 23 (8) (1997) 761 -770.

13 Gibaldi Milo & Perrier Donald, Pharmacokinetics (Marcel Dekker, New York) 1975.

14 Montgomery Dougl as C, Design and Analysis of experiments, 4th ed (John Wi ley & Sons, USA) 1996

15 Cochran W G, Statistical Methods , 6th edn (The Iowa State Uni versity Press, USA) 1967, 135-170.