269

CHAPTER -7

270

7.1 PREFORMULATION STUDIES

7.1.1 Determination of Valganciclovir solubility

Solubility assessment of Valganciclovir in various media of different pH

was carried as per the procedure described in the section 3.3.5 of Chapter 3.

7.1.2 Construction of Standard Calibration curve for Valganciclovir

Standard curve of Valganciclovir was calibrated according to the

general procedure described in the section 3.3.7 of Chapter 3.

7.1.3 Multimedia dissolution of Valganciclovir Marketed Formulations

Valganciclovir conventional marketed formulations were characterized

for drug release rate as per the method specified in the section 4.1.3 of

Chapter 4.

7.1.4 Fourier Transforms Infrared Radiation (FT-IR) Studies

The FT-IR spectrum was taken for pure Valganciclovir powder, initial

formulation and stability study samples according to the method described in

the 3.3.8 of chapter 3.

7.1.5 Differential scanning Calorimetry (DSC) Studies

Pure Valganciclovir powder, Initial formulation and stability samples

were characterized for thermal properties as per the method described in the

section 3.3.9 of chapter 3.

7.1.6 Analytical Methods

271

Ultraviolet Spectroscopy126

A novel, sensitive and precise UV spectroscopic method for

Valganciclovir was developed four different media to estimate the solubility,

dissolution and drug content in the designed formulations as per the

analytical method described in the 3.3.6 of chapter 3. Quantity of

Valganciclovir required was calculated from the relative regression equation of

the standard calibration curve.

7.1.7 Scanning Electron Microscopic (SEM) Studies

Morphological characterization of the prepared Valganciclovir

GRF Bilayered tablets was done by using Scanning electron microscope as

per the method given in the section 3.3.17 of Chapter 3. Valganciclovir GRF

Bilayered tablets prior to invitro dissolution assessment only were subjected

to SEM study.

7.2 Formulation of Non-Effervescent GRF Bilayered Tablets of

Valganciclovir

7.2.1 Characterization of Designed Formulations

In the present investigation Valganciclovir bilayered GRF tablets are

designed in order to retain in the stomach for prolonged time and release the

desired amount of Valganciclovir effectively with enhanced absorption by

maintaining effective plasma levels at the rate dictated by the needs of the

body with increased MRT.

272

Formulation and evaluation of Bilayered Valganciclovir Tablets includes

the following stages of its development.

1. Formulation and optimization of controlled release layer using various

polymers in different proportions by direct compression technique.

2. Formulation and optimization of gastric layer using various potential

polymers in different proportions by wet granulation technique.

3. Compression of Bilayered (Controlled release layer & Gastric layer) tablets

4. Evaluation of the prepared Bilayered tablet of Valganciclovir for various

properties like Drug content, Angle of repose, Bulk Density, Tapped

Density, Carr‘s Index...etc.

5. Evaluation of bilayered Valganciclovir tablets for buoyancy characteristics

like floating lag time and floating time.

6. Performance of in vitro dissolution studies of the bilayered Valganciclovir

tablet and to optimize the best formulation.

7.2.2 Moisture Uptake Studies of Lamivudine Formulations

In order to assign the desired environmental condition during the

manufacturing and storage, the designed and optimized Valganciclovir GRF

Bilayered tablets were subjected to moisture uptake study at different relative

humidity (RH) conditions100 like 33%, 54% and 90% RH as per the

methodology described in section 3.3.12 of Chapter 3.

7.2.3 Formulation of Controlled Release Layer of Valganciclovir

Various formulations (CF1-CF11) were prepared for controlled layer of

Bilayered tablet employing direct compression technique by taking

273

appropriate quantities of the ingredients as mentioned in the Table 7.5. All

ingredients are mixed intermittently by geometric dilutions and subjected to

compression using standard tabletting procedures as described in the section

3.3.4 of Chapter 3.

7.2.4 Formulation of Gastric Layer of Valganciclovir

Various formulations (GF1-GF8) were designed and prepared for the

gastric layer of Valganciclovir bilayered tablet by the standard wet

granulation technique with all the required ingredients as mentioned in the

Table 7.7. All the ingredients are mixed thoroughly by geometric dilutions and

subjected to compression using standard tabletting procedures as described

in the section 3.3.5 of Chapter 3.

7.2.5 Formulation of Non-Effervescent GRF Bilayered Tablets of

Valganciclovir

Optimized controlled release layer formulations and gastric layer

formulations were subjected to compression of bilayered tablets using

standard tabletting procedures. For distinguishing purpose opadry red dye of

low concentration was incorporated in gastric layer.

Controlled layer formulation was tabletted initially, to which the gastric

layer formulation granules were added and compressed. Caplet shaped

distinguished bilayered tablets were compressed and evaluated for the

required compendia parameters.

7.2.6 in vitro Buoyancy Studies82

in vitro buoyancy Studies were conducted for the evaluation of floating

lag time and floating duration time as per the method described in the section

3.3.13.2 of Chapter 3.

The results of in vitro Buoyancy Studies carried for Valganciclovir bilayered

GRF tablets are given in Table 7.9, 7.11, 7.13 and 7.15.

274

7.2.7 in vitro Drug Release Studies

The in vitro dissolution studies were performed for the Valganciclovir

bilayered tablets up to 12 hours using USP type II dissolution apparatus

(LABINDIA, DISSO-2000, Mumbai, India) at 100 rpm. Dissolution, sampling

and analytical methodology was given in the section 3.3.13.1 of Chapter 3.

in vitro drug release profiles were shown in Tables 7.6, 7.7, 7.11, 7.13

and 7.15

7.2.8 Kinetic Analysis of Release Data

Dissolution data of Valganciclovir bilayered GRF tablets was fitted to

five popular release linear and non linear models like Zero Order, First Order,

Higuchian Models, Erosion Model and Power Law to characterize the kinetics

of drug release from dosage forms. Curve fitting was done as described in

section 3.3.15 of Chapter3.

7.2.9 Statistical Comparison of Dissolution Profiles 103

Dissolution profiles were characterized and the similarity factor (f2

factor) was calculated to compare the dissolution profiles of different

formulations with the stability samples by the method described in the

section 3.3.16 of chapter 3.

7.2.10 Compatibility Studies By IR and DSC

7.2.10.1 Drug Excipient Compatibility Studies by IR Spectroscopy

Valganciclovir, Optimized Polymer, Valganciclovir + Optimized Polymer

- Physical mixture, Valganciclovir + optimized Polymer formulation discs were

prepared for FT-IR measurement as per the procedure described in the

section 3.3.8 of Chapter 3. The FTIR Spectra were given in Fig. 7.12 to 7.18.

275

7.2.10.2 Differential Scanning Calorimetry (DSC) Studies78

DSC study was carried out for Valganciclovir bilayered GRF tablets to

check if any incompatibility which occurs between the drug and the polymer.

The study was carried out for the optimized formulation and compared with

that of the standard as per the procedure given in section 3.3.9 of Chapter 3..

The DSC Thermograms are shown in Fig 7.19 to 7.25.

7.2.11 Accelerated stability studies on the prepared formulations102

Optimized formulations of prepared Valganciclovir GRF Bilayered

tablets were filled in HDPE containers and stored at the following conditions

like 40°C/75% RH for about 3 months as per ICH guidelines. The samples

were characterized for % drug content, FTIR and DSC study.

7.3 RESULTS AND DISCUSSIONS

7.3.1 Valganciclovir Solubility Determination

In pre-formulation studies, drug solubility assessment at different pH

conditions is the prime most consideration, as it directly simulates the drug

absorption throughout the GI tract106-108.

Valganciclovir has shown highest solubility in 0.1 N HCl and in pH 6.8

Phosphate buffer. The solubility of Valganciclovir in water is 124.81 mg/ml

where as in case of acetate buffer pH 6.8 the solubility is 189.37 mg/ml.

(Table 7.1) indicating the peak solubility of the drug in the pH range of 1 to 7.

Table 7.1: Solubility data of Valganciclovir in various pH media

Media

Solubility (mg/ml)

Water 124.81

0.1 N HCl 216.06

pH 4.5 Acetate buffer 76.48

pH 6.8 phosphate buffer 189.37

276

R² = 0.997

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0 5 10 15

Ab

sorb

an

ce

Conc (mcg)

CALIBRATION CURVE OF VALGANCICLOVIR

Fig: 7.1 Comparative Solubility Profiles of Valganciclovir in

Various pH Media

7.3.2 Construction of standard calibration curves for Valganciclovir126

Standard calibration curve was constructed by scanning the 20μg/ml

of Valganciclovir in 0.1N HCl. The standard graph of Valganciclovir in 0.1N

HCl has shown a good linearity with R2 of 0.997, in the concentration range

of 2-10 μg/ml.

Table – 7.2 Standard Calibration

Values of Valganciclovir Fig 7.2 Standard plot of Valganciclovir

0

50

100

150

200

250

Water 0.1 N HCl pH 4.5 Acetate buffer

pH 6.8 phosphate

buffer

Solu

bili

ty (m

g/m

l)

Media

Conc.(mcg) Absorbance

0

2 0.092

4 0.145

6 0.206

8 0.267

10 0.317

277

0

20

40

60

80

100

120

0 10 20 30 40 50

Cu

mu

lati

ve %

Dru

g R

elea

sed

Time (Minutes)

Dissolution Profile of Valganciclovir Tablets In Various Media

Water

0.1N Hcl

pH 4.5 Acetate BufferpH 6.8 Phosphate Buffer

7.3.3 Multimedia Dissolution of Valganciclovir Marketed Formulations

Multimedia dissolution assessment of Valganciclovir marketed

conventional formulations among different pH media (Table 8.2) has shown

similar release profiles with good correlation (Fig- 8.2) by releasing more than

90 % of drug within 10 minutes, clearly indicating the availability of drug at

the specific absorption site.

Table 7.3 in vitro Dissolution Profiles of Valganciclovir Tablets 100 mg

in Various pH Media

Fig. 7.3 Drug Release Rate of Marketed Valganciclovir Tablets

in Various pH Media

Time

(min)

Water

0.1 N HCl pH 4.5

Acetate buffer

pH 6.8

Phosphate buffer

5 86 ± 2.31 88 ±2.89 92 ±2.96 87 ±2.56

10 92 ±2.12 99 ±3.15 99 ±2.56 96 ±3.15

15 100 ±3.12 100 ±1.56 100 ±2.14 100 ±2.36

30 100 ±3.56 100 ±2.36 100 ±1.24 100 ±1.16

45 100 ±1.12 100 ±1.01 100 ±0.99 100 ±0.92

278

7.3.4 Fourier Transforms Infrared Radiation measurement (FT-IR) of

Pure Valganciclovir Drug

The FT-IR spectrum was taken for pure Valganciclovir powder.

as per the method described in the section 3.3.8 of Chapter 3.

Fig: 7.4 IR Spectrum of Valganciclovir Pure Drug

7.3.5 DSC Studies of Pure Valganciclovir Drug

Thermal characterization of pure Valganciclovir drug was done by by

Differential Scanning Calorimetry (DSC) studies as described in the section

3.3.9 of Chapter 3. DSC Thermogram of pure Valganciclovir drug was shown

in Fig: 7.5.

279

Fig No-7.5 DSC Thermogram of Valganciclovir

7.3.6 Analytical methods

UV spectra of Valganciclovir have show different absorption maxima in

varied media (Fig-4.6). A standard concentration of Valganciclovir in different

media was prepared and stored for 24 hours to assess the stability of the

Valganciclovir. Similar absorption spectra were observed among them with

similar λmax indicating the stable nature of the drug. (Table 7.4)

Table 7.4 λmax values of Valganciclovir in different pH media

Time Water 0.1NHCl pH 4.5 acetate

buffer

pH 6.8 phosphate

buffer

Initial 253.75 254.65 254.60 251.29

24 Hours 254.08 254.47 255.43 251.18

280

7.3.7 Formulation and Optimization of Controlled Release Layer of

Valganciclovir

Bilayered tablets are specialized dosage forms where in combination of

two or more drugs in a single unit having different release profiles at a

controlled fashion, which improves patient compliance, prolongs the drug(s)

action, avoid saw tooth kinetics resulting in effective therapy along with better

control of plasma drug levels.

Bilayered tablet formulations of Valganciclovir were optimized based

upon the release characteristics of controlled release layer and gastric layer in

addition to buoyancy characteristics.

Controlled release formulations CF1 to CF11 were prepared with the

aid of various potent acrylic polymers like Eudragit RS 100, Eudragit RL100,

Eudragit EPO, PEG 1000, PEG 6000, Eudragit S 100, and Eudragit L 100. All

the formulations were prepared by direct compression methods.

Table-7.5 Compositions of Valganciclovir Controlled Release Layer

Formulations (CF1- CF11)

INGREDIENTS

(mg) CF1 CF2 CF3 CF4 CF5 CF6 CF7 CF8 CF9 CF10 CF11

Valganciclovir 225 225 225 225 225 225 225 225 225 225 225

Eudragit RS100 50 -- -- -- -- -- -- -- -- --

Eudragit RL100 -- 50 -- -- -- -- -- -- 40 -- --

Eudragit EPO -- -- 50 -- -- -- -- 40 -- -- --

PEG 1000 -- -- -- 50 -- -- -- -- -- -- --

PEG 6000 -- -- -- -- 50 -- -- -- -- -- --

Eudragit S100 -- -- -- -- -- 50 -- -- -- -- 40

Eudragit L100 -- -- -- -- -- -- 50 -- -- 40 --

HPMC K4M 18 18 18 18 18 18 18 28 28 28 28

Microcrystalline

Cellulose 152.5 152.5 152.5 152.5 152.5 152.5 152.5 152.5 152.5 152.5 152.5

Magnesium

stearate 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5

281

0

20

40

60

80

100

120

0 5 10 15

% C

DR

TIME (Hours)

COMPARATIVE DRUG RELEASE PROFILE OF FORMULATIONS CF1-CF11 F1

F2F3F4F5F6F7F8F9F10F11

Table 7.6: Drug Release Profile of Valganciclovir Controlled Layer Formulations CF1 – CF11

Time CF1 CF2 CF3 CF4 CF5 CF6 CF7 CF8 CF9 CF10 CF11

0 0 0 0 0 0 0 0 0 0 0 0

0.5 31.32±0.20 31.32±0.56 31.08±0.32 36.12±0.11 58.32±0.32 37.2±0.63 41.64±0.82 20.28±0.43 30.12±0.88 24.24±0.73 25.2±0.53

1 39.24±0.28 42.35±0.45 54.12±0.55 53.52±1.11 60±0.36 50.64±0.21 45.6±0.54 30±0.31 46.32±1.02 40.2±0.42 33.36±0.61

2 43.36±0.45 53.4±0.91 78.84±0.22 85.68±0.64 85.2±0.21 73.08±0.53 79.92±0.25 46.8±0.58 60.6±0.43 62.16±0.49 72.84±0.37

4 56.21±0.83 59.04±0.56 83.28±0.68 90±0.41 89.4±0.10 90.84±0.56 91.5±0.85 70.56±0.75 66.72±0.87 72.44±1.43 76.2±1.32

6 61.2±0.85 64.12±0.27 95.44±0.33 91.44±0.82 94.56±1.11 95.76±0.84 92.96±1.32 71.92±0.92 72.04±0.36 88.64±0.76 87.62±0.29

8 74.64±0.36 78.24±0.66 98.12±0.21 96.24±0.82 97.44±1.24 95.62±0.46 80.16±0.34 84.36±0.55 96.37±0.22 91.43±1.12

10 80.69±0.48 82.2±0.43 90.58±0.22 88.27±0.66 93.67±0.53

12 90.17±0.86 93.39±0.77 94.43±0.59 92.23±1.32

Fig: 7.6 Comparative Drug Release of Valganciclovir Controlled Layer Formulations CF1-CF11

282

All the controlled release formulations CF1 to CF11 were assessed for

invitro drug release characteristics by standard dissolution testing

procedures through USP XXIV Dissolution Apparatus-II ( Model: Disso 2000,

M/s. Lab India). 900 ml of 0.1 N Hcl was used as dissolution medium,

maintained at a temperature of 37±0.5oC and the paddle was rotated at 50

RPM.

Controlled Formulations CF1 and CF2 comprising Eudragit RS 100

and Eudragit RL 100 had exhibited potential retardation by releasing

88.17% and 93.39% of drug respectively at the end of 12 hours.

CF3 formulation designed by Eudragit EPO has shown 95% of the

drug release 6 hours itself, which may not be desirable in view of the

objective to control the drug release up to 12 hours.

Controlled layer formulations CF4 to CF7 prepared by PEG 1000, PEG

6000, Eudragit S100, and Eudragit L100 has shown drug release of more

than 95%, but the polymers had retarded the release of drug only up to 8

hours, which is not desirable according to the objective of study to prolong

the drug release up to 12 hours.

Concentrations of Eudragit RL100, Eudragit EPO, Eudragit S100, and

Eudragit L100 were decreased and HPMC K4M concentration was slightly

increased in CF8, CF9, CF10 and CF11 respectively and subjected to

dissolution testing. Drug release was found to be increased in all the

formulations compared with that of high concentrations. Formulation CF8

and CF9 had retarded more than 90% of drug successfully upto 12 hours,

but the drug release was found to be highly inconsistent w.r.t dissolution

profiles, which may not meet the objective of the study that drug to be

released at a rate controlled and efficient manner.

By comparing the drug release profiles of all controlled layer

formulations CF 1 to CF11, formulation CF2 designed employing Eudragit

RL 100 was finally optimized as the best formulation for the controlled layer

283

of the bilayered tablet, as it had shown superior characteristics with respect

to drug release and rate retarding ability too.

7.3.8 Formulation and Optimization of Gastric Layer of Valganciclovir

Apart from controlled release layer optimization, suitable polymers

and their desired proportions are to be optimized towards gastric release

layer, since gastric layer plays predominant role in maintaining the required

buoyancy characteristics for the bilayered tablet of Valganciclovir. Various

formulations (GF1-GF8) were prepared for gastric layer of bilayered tablet

employing standard wet granulation technique and compressed as per the

standard tabletting procedures.

Various potential rate controlling polymers like HPMC K4M, HPMC

K100M, HPMC K15M, Eudragit RS100, Eudragit RL 100, Eudragit S100,

Eudragit L 100 and Eudragit EPO in equal proportions were employed along

with Carbopol 934 and Sodium alginate for Gastric formulations GF1 to

GF8.

Table7.7 Compositions of Valganciclovir Gastric Release Layer

Formulations (GF1- GF8)

INGREDIENTS (mg) GF1 GF2 GF3 GF4 GF5 GF6 GF7 GF8

Valganciclovir 225 225 225 225 225 225 225 225

HPMC K4M 30 -- -- -- -- -- -- --

HPMC K100M -- 30 -- -- -- -- -- --

HPMC K15M -- -- 30 -- -- -- -- --

Eudragit RS100 -- -- -- 30 -- -- -- --

Eudragit RL100 -- -- -- -- 30 -- -- --

Eudragit S100 -- -- -- -- -- 30 -- --

Eudragit L100 -- -- -- -- -- -- 30 --

Eudragit EPO -- -- -- -- -- -- -- 30

Carbopol 934 20 20 20 20 20 20 20 20

Sodium Alginate 15 15 15 15 15 15 15 15

Microcrystalline

Cellulose

155.5 155.5 155.5 150.5 155.5 155.5 155.5 155.5

Magnesium Stearate 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5

284

0

20

40

60

80

100

120

0 2 4 6 8 10 12 14

% C

DR

TIME ( Hours)

COMPARATIVE DRUG RELEASE PROFILE OF FORMULATIONS GF1-GF 8

F1

F2

F3

F4

F5

F6

F7

F8

Table 7.8 Cumulative % Drug Release Profile of Valganciclovir Gastric Layer

Formulations GF1-GF8

Time GF1 GF2 GF3 GF4 GF5 GF6 GF7 GF8

0 0 0 0 0 0 0 0 0

0.5 9.32±0.65 11.21±0.53 10.37±0.36 21.96±0.37 14.95±0.94 13.86±0.52 14.68±1.26 13.35±0.21

1 14.66±0.58 18.36±0.21 13.59±0.12 27.84±0.21 21.38±0.63 23.28±0.36 22.69±0.63 21.52±0.45

2 26.32±1.10 29.85±0.83 23.75±0.64 41.49±0.73 36.28±0.26 43.31±0.72 35.77±0.28 32.95±0.68

4 41.25±0.93 38.29±0.63 28.16±0.35 52.4±0.86 47.76±0.44 54.27±0.53 46.2±1.27 43.22±0.98

6 52.21±0.64 47.32±0.25 34.43±0.43 61.96±1.32 58.92±0.26 59.42±0.84 59.98±0.62 58.64±0.433

8 59.73±0.41 56.13±0.96 48.74±0.53 74.24±0.39 66.35±1.52 61.39±0.47 63.36±1.46 61.37±1.21

10 66.38±0.27 62.35±0.77 53.38±0.40 83.29±1.05 70.38±0.94 77.81±0.82 71.12±0.53 69.34±0.87

12 79.27±0.85 72.11±0.28 67.71±0.68 95.41±0.47 89.44±0.24 88.22±1.42 82.06±0.37 78.28±0.94s

Fig: 7.7 Comparative Drug Release Profiles of Valganciclovir Gastric Layer

Formulations GF1-GF8

285

All the respective polymers in the gastric layer formulations GF1 to

GF8 in association with Carbopol934 and Sodium alginate had successfully

retarded the drug up to 12 hours. Among all the formulations that were

subjected to dissolution characterization, GF4 designed by employing

Eudragit RS100 had shown good release characteristics of about 95% in 12

hours, which provides the basis for its optimization as the best gastric layer

formulation apart from its buoyancy characters.

All the gastric layer formulations GF1 to GF8 were subjected to invitro

buoyancy studies at agitation conditions for evaluation of buoyancy lag time

and duration of floating characteristics. Results of buoyancy studies were

tabulated as Table 7.9

Table 7.9: Buoyant Characteristics of Valganciclovir Gastric Layer

Formulations GF1 –GF8

GASTRIC

FORMULATION

BUYOYANCY

LAG TIME

(Minutes)

DURATION OF

FLOATING

GF 1 40 >12 Hours

GF 2 50 4.5 Hours

GF 3 40 > 8 Hours

GF 4 22 >12 Hours

GF 5 34 >12 Hours

GF 6 -- --

GF 7 42 6-7 Hours

GF 8 -- --

GF1, GF4 and GF5 formulations had exhibited excellent buoyancy

characteristics by maintaining their integrity for more than 12 hours, which

shows the consistent floating ability of the respective polymers by hydrogel

formation upon wetting.

GF2 and GF3 formulations had shown poor floating characteristics by

being buoyant only up to 4.5 hours and 8 hours respectively.

GF6 and GF8 formulations failed to exhibit their buoyancy ability, as

they failed to float even after a long lag of observation.

286

Since no effervescent or gas generating agents were used, all the

gastric formulations has shown buoyancy lag time from minimum of 22

minutes to maximum of 50 min, as the study pertains to the development of

non-effervescent dosages forms basing on the hydrogel forming ability of the

potential polymers selected.

7.3.9 Formulation and Optimization of Non-Effervescent Bilayered

Tablets of Valganciclovir

Among the controlled release formulations [CF1 – CF11] prepared,

Formulation CF2 with the aid of Eudragit RL 100 polymer is selected as

optimized formulation basing on its controlled release retarding ability.

Among the Gastric release formulations [GF1 – GF11] prepared,

formulation GF4 with the Eudragit RS 100 is selected as optimized

formulation basing on its controlled release retarding ability and better

buoyancy characteristics.

Bilayered tablets were prepared by direct compression procedure

employing the standard tabletting methods.

Table-7.10 Composition of Valganciclovir Bilayered Formulation (BLF)

CONTROLLED LAYER GASTRIC LAYER

INGREDIENTS

(mg)

COMPOSITION

(mg)

INGREDIENTS

(mg)

COMPOSITION

(mg)

Valganciclovir 225 Valganciclovir 225

Eudragit RL 100 50 Eudragit RS 100 30

HPMC K4M 18 Carbopol 934 20

Microcrystalline

Cellulose 152.5 Sodium Alginate 15

Magnesium Stearate 4.5 Microcrystalline

Cellulose 155.5

Magnesium Stearate 4.5

287

Table 7.11 Drug Release Data, Buoyant Characteristics of

Valganciclovir Bilayered Formulation (BLF)

TIME %DRUG

RELEASE

BUOYANCY

LAG TIME

DURATION OF

FLOATING

0 0

Not Floating --

30 20.28±0.31

1 31.13±0.56

2 46.87±0.84

4 54.62±1.22

6 71.92±0.32

8 81.16±0.88

10 86.24±1.59

12 92.66±0.63

Bilayered Formulation (BLF) compressed employing CF2 Formulation

of controlled release layer and GF5 Formulation of Gastric layer were

subjected to invitro dissolution studies and invitro buoyancy studies. BLF

had shown good release characteristics of more than 92% at the end of 12

hours but the buoyancy characteristics were found to be totally poor

without any floating behavior, which claims the necessity to optimize the

Bilayered formulation for its floating characteristics.

Optimization of Bilayered Formulation

Table – 7.12 Composition of Valganciclovir Bilayered Formulation (BLF 1)

CONTROLLED LAYER GASTRIC LAYER

INGREDIENTS

(mg)

COMPOSITION

(mg)

INGREDIENTS

(mg)

COMPOSITION

(mg)

Valganciclovir 225 Valganciclovir 225

Eudragit RL 100 50 Eudragit RS 100 30

HPMC K4M 18 Carbopol 934 22

Microcrystalline

Cellulose 152.5 Sodium Alginate 18

Magnesium Stearate 4.5 Microcrystalline

Cellulose 150.5

Magnesium Stearate 4.5

288

Table-7.13 Drug Release Data, Buoyant Characteristics of

Valganciclovir Bilayered Formulation (BLF1)

TIME %DRUG

RELEASE

BUOYANCY

LAG TIME

DURATION

OF

FLOATING

0 0

38

Minutes

More than

12 Hours

30 24.24±0.74

1 28.92±0.83

2 30.12±0.32

4 46.32±1.05

6 60.6±0.63

8 80.04±0.49

10 84.36±0.39

12 89.96±1.16

Carbopol and Sodium alginate concentrations were slightly increased

in BLF and designed as BLF1 formulation and subjected to invitro

dissolution studies and invitro buoyancy studies. BLF 1 had shown around

89% of drug release at the end of 12 hours, which is slightly less than that

of BLF. Buoyancy characteristics were found to be better with a buoyancy

floating lag time of 38 min and duration of floating being more than 12

hours, which might be due to the gelling ability of Carbopol and Sodium

alginate in addition to the hydrogel formed by Eudragit RL 100 and Eudragit

RS 100.

38 minutes of floating lag time is too long and tedious, which may not

be considerable aspect with respect to the objective of the present study.

289

Table -7.14 Composition of Valganciclovir Bilayered Formulation BLF -02

CONTROLLED LAYER GASTRIC LAYER

INGREDIENTS

(mg) COMPOSITION(mg)

INGREDIENTS

(mg) COMPOSITION(mg)

Valganciclovir 225 Valganciclovir 225

Eudragit RL 100 50 Eudragit RS 100 30

HPMC K4M 18 Carbopol 934 25

Microcrystalline

Cellulose 152.5 Sodium Alginate 12

Magnesium

Stearate 4.5

Microcrystalline

Cellulose 153.5

Magnesium

Stearate 4.5

Table- 7.15 Drug Release Data, Buoyant Characteristics of

Valganciclovir Bilayered Formulation (BLF2)

TIME %DRUG

RELEASE

BUOYANCY

LAG TIME

DURATION

OF

FLOATING

0 0

29

Minutes

More than

12 Hours

30 21.63±0.48

1 30.12±1.28

2 48.74±0.73

4 61.92±0.21

6 69.61±1.32

8 78.76±0.11

10 86.53±0.36

12 91.38±0.51

290

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15

% C

DR

Time ( Hours)

COMPARATIVE DRUG RELEASE PROFILES OF BILAYERED FORMULATIONS

BLF

BLF1

BLF2

In BLF 2, Carbopol concentration was slightly increased and Sodium

alginate concentration was slightly decreased, subjected to invitro

dissolution studies and invitro buoyancy studies. Drug release was found to

be increased up to 94% and floating lag time was decreased to 29 minutes,

which is encouraging compared to that of previous BLF and BLF1

formulations.

29 minutes of floating lag time is bit high in floating drug delivery

systems which may result in the dosage form to get emptied from stomach

to the intestine region, but the presence of Carbopol 934 in the Bilayered

formulation due to its bio adhesive nature, it may assist the dosage form to

adhere to the gastric lining there by blocking the possibility of bilayered

tablet from getting emptied to the intestine from stomach region.

Fig: 7.8 Comparative Drug Release Profiles of Valganciclovir Bilayered

Formulations BLF, BLF1, BLF2

291

0 10 20 30 40 50

GF1

GF2

GF3

GF4

GF5

GF6

GF7

GF8

BLF

BLF1

BLF2

BUOYANCY LAG TIME

Fig- 7.9 Buoyancy Lag Time Details of Gastric Layer Formulations and

Bilayered Formulation

7.3.10 ANALYSIS OF RELEASE DATA

Dissolution data of all the designed formulations were fitted to

popular model dependent approaches viz. Zero Order, First Order,

Higuchian Model, Erosion Model and Power Law (Korsemeyer Pappas Model)

in order to assess the drug release kinetics.

Time (Min)

292

0

0.5

1

1.5

2

2.5

0 5 10 15L

OG

% U

ND

ISSO

LV

ED

TIME (Hours)

REGRESSION PLOT-FIRST ORDER (CF1 - CF11)CF1

CF2

0

50

100

150

200

0 5 10 15

CU

MU

LATI

VE

DR

UG

R

ELEA

SE (

CD

R)

TIME

REGRESSION PLOT-ZERO ORDER (CF1 - CF11)

CF1

CF2

0

50

100

150

200

0 1 2 3 4

CU

MU

LA

TIV

E D

RU

G

RELEA

SE (

CD

R)

SQRT TIME

REGRESSION PLOT-HIGUCHIAN MODEL (CF1 - CF11)

CF1

CF2

REGRESSION PLOTS OF CONTROLLED RELEASE FORMULATIONS

Fig: 7.10 Regression Plots of Valganciclovir

Controlled Release Formulations (C1-C11)

REGRESSION PLOTS –

CONTROLLED RELEASE FORMULATION

(CF1 TO CF11)

0

2

4

6

8

10

12

0 5 10 15

1-[

1-Q

]1/

3

TIME (hrs)

REGRESSION PLOT- EROSION MODEL(CF1 - CF11)

CF1

CF2

CF3

CF4

CF5

CF6

0

0.5

1

1.5

2

2.5

0 0.5 1 1.5

LO

G C

DR

LOG TIME

REGRESSION PLOT-POWER LAW (CF1 - CF11)

CF1

CF2

Table – 7.16 Relative Regression Coefficient Values of

Valganciclovir Controlled Release Formulations (CF1-CF11)

CONTROLLED

FORMULATIONS

ZERO

ORDER

(r)

FIRST

ORDER

(r)

HIGUCHI

(r)

EROSION

(r)

POWER LAW

(n)

CF1 0.913 0.854 0.969 0.405 0.635

CF2 0.924 0.825 0.953 0.387 0.729

CF3 0.841 0.632 0.931 0.414 0.590

CF4 0.955 0.604 0.872 0.407 0.556

CF5 0.826 0.603 0.811 0.489 0.661

CF6 0.932 0.711 0.929 0.305 0.596

CF7 0.881 0.807 0.890 0.386 0.702

CF8 0.939 0.876 0.977 0.280 0.568

CF9 0.948 0.864 0.935 0.375 1.635

CF10 0.952 0.722 0.979 0.455 0.626

CF11 0.943 0.897 0.911 0.421 0.723

294

REGRESSION PLOTS OF GASTRIC LAYER FORMULATIONS

Fig : 7.11 Regression Plots of Valganciclovir Gastric Layer

Formulations (GF1-GF8)

REGRESSION PLOTS –

GASTRIC LAYER FORMULATION

(GF1 TO GF8)

Table 7.17: Relative Regression Coefficient Values of

0

20

40

60

80

100

120

0 5 10 15

CU

MU

LA

TIV

E D

RU

G

RELEA

SE(C

DR

)

TIME(Hours)

REGRESSION PLOT-ZERO ORDER (GF1 - GF8)

GF1

GF2

0

0.5

1

1.5

2

2.5

0 5 10 15

LO

G%

UN

DIS

SOLV

ED

TIME(Hours)

REGRESSION PLOT-FIRST ORDER (GF1 - GF8)

GF1

GF2

-20

0

20

40

60

80

100

120

0 1 2 3 4CU

MU

LATI

VE

DR

UG

REL

EASE

(C

DR

)

SQRT TIME

REGRESSION PLOT-HIGUCHIAN MODEL

(GF1 - GF8)GF1

GF2

GF3 0

1

2

3

4

5

6

7

0 5 10 15

1-[

1-Q

]1/

3

TIME(Hours)

REGRESSION PLOT-EROSION MODEL (GF1 - GF8)

GF1

GF2

GF3

GF4

GF5

GF6

GF7

0

0.5

1

1.5

2

2.5

0 0.5 1 1.5

LO

G %

DR

UG

RELEA

SE

LOG TIME

REGRESSION PLOT- POWER LAW(GF1 - GF8)

GF1

GF2

GF3

295

Valganciclovir Gastric Layer Formulations (GF1-GF8)

GASTRIC LAYER

FORMULATIONS

ZERO

ORDER

(r)

FIRST

ORDER

(r)

HIGUCHI

(r)

EROSION

(r)

POWER LAW

(n)

GF1 0.960 0.982 0.989 0.581 0.645

GF2 0.944 0.985 0.995 0.530 0.562

GF3 0.968 0.960 0.961 0.560 0.575

GF4 0.932 0.910 0.994 0.932 0.623

GF5 0.932 0.918 0.987 0.520 0.525

GF6 0.893 0.935 0.972 0.497 0.515

GF7 0.920 0.976 0.994 0.520 0.532

GF8 0.925 0.983 0.995 0.511 0.584

Table -7.18 Relative Regression Coefficient Values of

Valganciclovir Bilayered Formulations

BILAYERED

FORMULATION

ZERO

ORDER

(r)

FIRST

ORDER

(r)

HIGUCHI

(r)

EROSION

(r)

POWER LAW

(n)

BLF 0.901 0.766 0.990 0.380 0.532

BLF1 0.919 0.754 0.997 0.500 0.560

BLF2 0.923 0.760 0.985 0.512 0.581

All the formulations were found to have following typical Zero

order kinetics which was clearly indicated by their relatively higher ―r‖

values compared to that of First order regression co efficient values.

All the formulations were found to be accepting Higuchian

diffusion as release model, indicated by their relatively higher ―r‖

values compared to that of Erosion model regression coefficient

values.

296

The dissolution data of all formulations were fitted to the Power

law (Korsemeyer Pappas model) and the entire exponent ―n‖ values

were found to be between 0.5-1, indicating that all the formulations

were following Non-Fickian mode of drug release.

7.3.11 Drug – Excipient Compatibility Study by IR and DSC

7.3.11.1 FTIR Spectroscopic Studies of Optimized Bilayered

Tablets of Valganciclovir

Infrared spectroscopy is a successful analytical technique being

employed to check if any the chemical interactions occur between the

drug and the other excipients used in the formulations.

IR spectra of pure drug, optimized polymers, physical mixture of

optimized formulation and optimized bilayered tablet formulation were

shown in Fig: 7.12, 7.13, 7.14, 7.15, 7.16, 7.17 and 7.18 respectively

Fig: 7.12 IR Spectrum of Valganciclovir Pure Drug

297

Fig: 7.13 IR Spectrum of Eudragit RL 100

Fig: 7.14 IR Spectrum of Eudragit RS 100

298

Fig: 7.15 IR Spectrum of Carbopol 934

Fig: 7.16 IR Spectrum of HPMC K4M

299

Fig: 7.17 IR Spectrum of Drug + Polymer(S) - Physical Mixture

Fig: 7.18 IR Spectrum of Drug + Polymer(S) - Optimized Bilayered

Tablet Formulation

300

By carrying out drug and polymer compatibility studies, it was

assessed and concluded that that there was no interaction between

the drug and polymer, as the principle peaks of the drug were found

to be unaltered and the respective regions of the IR spectra .

7.3.11.2 Differential Scanning Calorimetric (DSC) Studies of

Optimized Bilayered Tablets of Valganciclovir

DSC is an advanced technique by which the heat flows to or

from a reference, which is monitored as a function of temperature or

time, while the samples are subjected to a controlled temperature

program.

Lopinavir+ Ritonavir, Optimized Polymer (Geleol Pastilles+

Myrj52), Physical mixture of Lopinavir+ Ritonavir + Optimized

Polymer( Geleol Pastilles+ Myrj52, Optimized formulation of Lopinavir+

Ritonavir + Optimized Polymer( Geleol Pastilles+ Myrj52 )formulations

were subjected to DSC studies to check the compatibility among

them.

DSC Thermograms of pure drug, pure optimized polymers,

optimized formulation physical mixture and optimized bilayered Tablet

formulation were shown in Fig: 7.19, 7.20, 7.21, 7.22, 7.23, 7.24 and

7.25 respectively

Fig : 7.19 DSC Thermogram of Valganciclovir Pure Drug

301

Fig: 7.20 DSC Thermogram of HPMC K4M

Fig: 7.21 DSC Thermogram of Carbapol 934

302

Fig: 7.22 DSC Thermogram of Eudragit RS-100

Fig: 7.23 DSC Thermogram of Eudragit RL-100

303

Fig: 7.24 DSC Thermogram of Optimized Valganciclovir

Formulation Physical Mixture

Fig : 7.25 DSC Thermogram of Optimized Bilayered Tablet

Formulation BF 2

304

7.3.12 Moisture uptake studies of Optimized Bilayered Tablets of

Valganciclovir

Optimized GRF Bilayered tablets of Valganciclovir which were

formulated in different combination and proportions of various polymers

were exposed to different relative humidity (RH) conditions. Comparatively

less moisture uptake was observed in both granules and tablets at 33 % RH

and higher moisture uptake was observed at above 90 % RH. The moisture

uptake by granules and tablets was proportional to that of percent relative

humidity (RH). Due to larger surface area the moisture uptake of granules

was found to be more than tablets (Table 7.19 and Fig 7.26) and later on

after certain time period equilibrium moisture was attained.

Table 7.19 Percent of moisture uptake of Valganciclovir Granules and

Bilayered Tablets Formulation BLF 2

% Humidity Moisture uptake in % w/w

Time 24 Hrs 48Hrs 72 Hrs 96 Hrs 120 Hrs

Granules

33% 0 0.027 0.033 0.045 0.046

54% 0.208 0.32 0.341 0.365 0.365

90% 1.551 1.863 1.982 2.113 2.125

Bilayered

Tablets

33% 0.009 0.012 0.023 0.031 0.039

54% 0.117 0.224 0.256 0.262 0.269

90% 1.145 1.206 1.262 1.291 1.336

305

The results of moisture uptake study reveals and give an idea

about assigning proper storage condition for granules and final

formulation during the manufacturing and further usage.

Fig. 7.26 Percent Moisture Uptake vs. Time Plots of Bilayered

Tablets of Valganciclovir

(G is granules at 33% RH, G is granules at 54% RH, G granules

at 90 % RH, T is tablets at 33 % RH , T is tablets at 54% RH and

T tablets at 90 % RH)

7.3.13 Accelerated Stability Studies of Optimized Bilayered

Tablets of Valganciclovir

Percent assay and dissolution rate of accelerated stability

studies subjected samples at 1, 2, and 3 months of optimized

Valganciclovir bilayered GRF formulation BLF2 had shown

satisfactory results. The similarity factor (f-2) was calculated (Table

7.20) and compared to initial dissolution and it was found to be more

than 77. The comparative dissolution profile plots of stability samples

0

0.5

1

1.5

2

2.5

0 50 100 150

% M

ois

ture

Up

take

Time (Hours)

Moisture Absorption Studies

G-33% RH

G-54% RH

G-90% RH

T-33% RH

T-54% RH

T-90% RH

306

have shown good correlation with initial samples. (Fig 7.27) indicating

the stable nature of the optimized Valganciclovir bilayered GRF

formulation (BLF 2).

7.20 Dissolution and Assay of Bilayered Tablets of Valganciclovir

During Stability (n=3)

Time Stavudine Multi Unit GRFDDS Formulation F-7

0 M 1 M 2 M 3M

2 48.74±0.73 47.63(±1.9) 47.20(±3.1) 47.26(±2.8)

6 69.61±1.32 69.29(±1.1) 67.25(±3.6) 68.19(±2.3)

8 78.76±0.11

79.21(±1.1) 79.41(±2.7) 78.22(±2.7)

10 86.53±0.36

85.16(±2.1) 86.12(±1.1) 85.41(±1.1)

12 91.38±0.51

92.38(±3.1) 92.73(±1.1) 93.61(±3.1)

f-2 - 78(±2.6) 80(±2.2) 79(±1.1)

Assay 99.21 99.56 99.63 100

f-2- similarity factor

Fig. 7.27 Comparative Cumulative Percent Released vs. Time

Plots of Bilayered Tablets of Valganciclovir-

Initial, 1, 2 and 3 months at 40°C/75% RH

0

20

40

60

80

100

0 5 10 15

C%

CD

R

Time (Hours)

Accelerated Stability Studies

BF2- Initial (0 Months)

"BF2- 1 Month @ 40oC / 75% RH

"BF2- 2 Month @ 40oC / 75% RH

"BF2- 3 Months @ 40oC / 75% RH

307

7.3.14 Scanning Electron Microscopy (SEM) Studies

Scanning electron microscopy studies of the present

Valganciclovir BGF tablet formulation was mainly carried out for the

examining the surface of polymeric drug delivery system which may

provide important information about the porosity and microstructure

of the device.

Fig No- 7.28 Scanning Electron Microscope Photographs of

Optimized Valganciclovir Formulation

500 X ( Dry Surface) 500 X ( 4 Hours Swelling)

500 X ( 6 Hours Swelling) 500 X ( 12 Hours Swelling)

From the SEM studies, it was observed that as the time

increases the swelling ability and the porosity of the tablet was found

to be increased, which mainly helps to drug to release from the

bilayered tablet formulation at rate effective and controlled manner.