Formulation Development and Comparative Study of Clopidogrel Bisulfate Matrix Formulations

 

Lankesh P. Shewale¹*, Sheetal B. Gondkar¹, Ravindra B. Saudagar², Avinash B. Dareker³

¹Department of Pharmaceutics, Ravindra Gambhirrao Sapkal College of  Pharmacy, Anjaneri, Nashik, Maharashtra, India.

 

ABSTRACT:

The objective of this study was to design matrix tablets for oral sustained release of clopidogrel bisulfate and to investigate the sustained release behavior of the matrix tablets. Matrices were prepared by direct compression technique, melt method and microencapsulation using sodium carboxymethylcellulose, carnuba wax and ethyl cellulose as a release retardant. The FT-IR analysis indicated the stability and compatibility of drug with excipients. The formulation was optimized on the basis of acceptable tablet properties and invitro drug release. The resulting formulations produced tablets with optimum hardness, uniform thickness, consistent weight uniformity and low friability. The results of dissolution studies indicated that formulations F2 batch exhibited good drug release pattern to provide sufficient concentration for achieving satisfactory therapeutic value for extended period of time. The drug release from F2 formulation was sustained upto 12 hrs. Tablet Fitting in-vitro drug release data from optimized matrix formulation to Korsmeyer Pappas model equation indicated that diffusion and erosion could be mechanism of drug release. Matrix tablet F2 showed no change in physical appearance, drug content after storage 40⁰C, 75% RH for 3 months.

 

 

 

SUSTAINED RELEASE CONCEPT:

One of the first commercially available products to provide sustained release of a drug was Dexedrine Spansules, made by Smith Kline and French. After this many more sustained-release products came to the market, some successful, others potentially lethal. Each delivery system was aimed at eliminating the cyclical changes in plasma drug concentration seen after the administration of a conventional delivery system.

 

Sustained release systems include any drug delivery system that achieves slow release of drug over an extended period of time. If the system is successful in maintaining constant drug levels in the blood or target tissue, it is considered as a controlled-release system. If it is unsuccessful at this but nevertheless extends the duration of action over that achieved by conventional delivery, it is considered as a prolonged release system. The oral route of administration for sustained release systems has received greater attention because of more flexibility in dosage form design. The design of oral sustained release delivery systems is subjected to several interrelated variables of considerable importance such as the type of delivery system, the disease being treated, the patient, the length of therapy and the properties of the drug.

Sustained release, sustained action, prolonged action, controlled release, extended action, timed release, depot and repository dosage forms are terms used to identify drug delivery systems that are designed to achieve prolonged therapeutic effects by continuously releasing medication over an extended period of time after administration of single dose.

 

Sustained release and controlled release will represent separate delivery processes; sustained release constitutes any dosage from that provides medication over an extended period of time. Controlled release however, denotes that, system is able to provide same actual therapeutic control, whether this is temporal nature, spatial nature, or both. In other words, the system attempts to control drug concentration in target tissue. This correctly suggests that there are sustained-release systems that cannot be considered as controlled release.

 

The following are the rationale of developing SR:

·        To extend the duration of action of the drug

·        To reduce the frequency of dosing

·        To minimize the fluctuations in plasma level

·        Improved drug utilization

·        Less adverse effects

·        Limitations of SR products are as follows:

·        Increase of drug cost.

·        Variation in the drug level profile with food intake and from one subject to another.

 

Advantages of SR Matrix DDS:

1.   The frequency of drug administration is reduced.

2.   Patient compliance can be improved.

3.   Drug administration can be made more convenient as well.

4.   The blood level oscillation characteristic of multiple dosing of conventional dosage forms is reduced.

5.   Better control of drug absorption can be attained, since the high blood level peaks that may be observed after administration of a dose of a high availability drug can be reduced.

6.   The characteristic blood level variations due to multiple dosing of conventional dosage forms can be reduced.

7.   The total amount of drug administered can be reduced, thus: Maximizing availability with minimum dose. Minimize or eliminate local side effects · Minimize or eliminate systemic side effects Minimize drug accumulation with chronic dosing

8.   Safety margins of high potency drugs can be increased and the incidence of both local and systemic adverse side effects can be reduced in sensitive patients.

9.   Improve efficiency in treatment, cure or control condition more promptly, improve control of condition · Improve bioavailability of some drugs, Make use of special effects; e.g. sustain release aspirin for morning relief of arthritis by dosing before bed-time.

10.Economy.

 

Disadvantages of SR matrix DDS:

1.   Probability of dose dumping.

2.   Reduced potential for dose adjustment.

3.   Cost of single unit higher than conventional dosage forms.

4.   Increase potential for first pass metabolism.

5.   Requirement for additional patient education for proper medication.

6.   Decreased systemic availability in comparison to immediate release conventional dosage forms.

7.   Poor in vitro and in vivo correlations.

 

MATERIALS AND METHOD:

Materials:

Clopidogrel bisulfate was obtained as gift sample from Macleods Pharmaceuticals Mumbai, Sodium carboxymethylcellulose, Ethyl cellulose, Carnuba wax and Cyclohexanewere purchased from Research-lab Fine Chem. Industry- Mumbai.

 

Methods:^[6-14]

UV-Visible Spectroscopy:

Determination of λmax in phosphate buffer solution pH 6.8:

The UV spectrum of Clopidogrel bisulfate was obtained using UV Jasco V630. Accurately weighed 100 mg of the drug was dissolved in sufficient quantity of methanol and volume made up with pH 6.8 PBS. The stock solution was diluted to obtain a concentration of 1000 µg/ml. 1.5 ml of aliquot was withdrawn and  volume was made upto 10 ml using  respective solvent to obtain the concentration of 150 µg/ml. The resultant solution was scanned from 400 to 200 nm and the spectrum was recorded to obtain the value of maximum Wavelength in respective solvent.

 

Infra-Red Spectrum:

The infrared absorption spectrum of Clopidogrel bisulfate was recorded with  the wave number 4000 to 400 cm^-1 by using Fourier transform infrared spectrophotometer .(Brukar)

 

Formulation of Clopidogrel bisulfate matrix tablet:

Different polymers were employed in order to formulate matrix tablet of drug. Different drug: polymers ratios were employed as 1:0.5, 1:1,and 1:1.5 were prepared by two methods as direct compression method and melt method. Polymers employed were Sodium CMC and Carnuba Wax. Compositions of different formulations are shown in Table no.1.

 

Direct Compression method:^[15]

Drug, polymers and other excipients were weighed separately for each formulation. The tablets were prepared by direct compression method. Active ingredient (Clopidogrel bisufate) and polymer Na- CMC were passed through #85sieve and placed in a poly bag. Then these ingredients were mixed in apoly bag for 5 minutes. After mixing, MCC, Aerosil and Magnesium Stearate were passed through #85 sieve and placed in the same polybag and were mixed for 3 minutes. Blend were discharged into the double polythene bags and closed properly.Blend was then compressed using Rotary tablet minipress-I (Rimek, Karnavati Engineering Ltd., Mehsana, Gujarat) equipped with 6.0 mm round biconvex punch and dieset. After compression, the prepared tablets were stored in an airtight container for further evaluation.

 

Melt method:^[16]

Drug, polymers and other excipients were weighed separately for each formulation. The tablets were prepared by direct compression method. Carnuba wax was heated at above melting point on a water bath to obtain melted wax mass. In melted wax mass drug was dispersed with continuous stirring to obtain a homogenous melt. Then that molten mass was allowed to cool at room temperature to obtain a blend. To that blend MCC was added and then aerosil, mg. sterate. Blend was then compressed using Rotary tablet minipress-I (Rimek, Karnavati Engineering Ltd., Mehsana, Gujarat)equipped with 6.0 mm round biconvex punch and dieset. After compression, the prepared tablets were stored in an airtight container for further evaluation.

 

 

Table No.1: Formulation of Clopidogrel bisufate matrix tablet

Ingredients	F1 (1:0.5)	F2 (1:1)	F3  (1:1.5)	F7 (1:0.5)	F8 (1:1)	F9 (1:1.5)
Clopidogrel bisulfate	75	75	75	75	75	75
Sodium CMC	12.5	25	37.5	_	_	_
Carnuba Wax	_	_	_	12.5	25	37.5
MCC	85.5	73	60.5	85.5	73	60.5
Aerosil	1	1	1	1	1	1
Mg.stearate	1	1	1	1	1	1
Total	175	175	175	175	175	175

(All quantities were in mg)

 

Formulation of Clopidogrel bisulfate capsule:

Different polymers were employed in order to formulate capsule of drug. Different drug: polymers ratios were employed as 1:0.5, 1:1, 1:1.5 and 1:2.5 were prepared by three methods as capsule filling, microencapsulation method, and melt method. Polymers employed were Sodium CMC, Ethyl Cellulose, and Carnuba wax. Compositions of different formulations are shown in Table no.2.

 

The entire capsules were filled in empty capsule shell (size1) by capsule filling.

 

Phase-separation/ coacervation microencapsulation method:^[17]

Drug and polymers were weighed separately for each formulation. Cyclohexane was measured about 25ml. Cyclohexane is insoluble at room temperature with ethylcellulose, but at elevated temperature it is soluble. Ethylcellulose (EC) was weight and was dispersed in cyclohexane at about 80°c to form a homogeneous polymer solution on an electric water bath; to that solution with continuous stirring the drug is added. Mixture was cooled further to room temperature for accomplishes gelation and solidification of the coating; effects phase separation/coacervation of the core material. The microencapsulated product was collected by filtration and then filled in empty capsule shell.

 

Figure 1:Coacervation process: (a) Core material dispersion in solution of shell polymer; (b) Separation of coacervate from solution; (c) Coating of core material by micro droplets of coacervate; (d) Coalescence of coacervate to form continuous shell around core particles.

 

Melt method:

Drug, polymers and other excipients were weighed separately for each formulation. Carnuba wax was heated at above melting point on a water bath to obtain melted wax mass. In melted wax mass drug was dispersed with continuous stirring to obtain a homogenous melt. Then that molten mass was allowed to cool at room temperature to obtain a blend. To that blend MCC was added and then aerosil, mg. sterate. Blended granules were then filled in empty capsule shell.

 

Table No.2: Formulation of Clopidogrelbisulfate capsules

Ingredients	F10 (1:0.5)	F11 (1:1)	F12  (1:1.5)	F4 (1:0.5)	F5 (1:1)	F6 (1:2.5)	F13 (1:0.5)	F14 (1:1)	F15 (1:1.5)
Clopidogrel bisulfate	75	75	75	75	75	75	75	75	75
Sodium CMC	12.5	25	37.5	_	_	_	_	_	_
Ethyl Cellulose	_	_	_	12.5	25	63	_	_	_
Carnuba Wax	_	_	_	_	_	_	12.5	25	37.5
MCC	85.5	73	60.5	_	_	_	85.5	73	60.5
Aerosil	1	1	1	_	_	_	1	1	1
Mg.stearate	1	1	1	_	_	_	1	1	1
Total	175	175	175	87.5	100	138	175	175	175

 (All quantities are in mg)

 

Capsule filling:

Drug, polymers and other excipients were weighed separately for each formulation. Active ingredient (Clopidogrel bisulfate) and polymer Na- CMC were passed through #85sieve and placed in a poly bag. Then these ingredients were mixed in a poly bag for 5 minutes. After mixing, MCC, Aerosil and Magnesium Stearate were passed through #85 sieve and placed in the same poly bag and were mixed for 3 minutes. Blend was discharged into the double polythene bags and closed properly. Blend was then filled in empty capsule shell.

 

Evaluation of Bulk used for tablet and capsule^[18]

Bulk density:

The bulk density was obtained by dividing the mass of powder by the bulk volume. The sample equivalent to 10 g was accurately weighed and filled in a 100 mL graduated cylinder and the powder was leveled and the unsettled volume, (V0) was noted. The bulk density was calculated by the formula

 

 

 

Where, ρ0 = Bulk density,

M = Mass of powder taken andV0 = Apparent unsettled volume.

 

Tapped density:

The tapped density was determined by mechanically tapping the measuring cylinder or by using the digital bulk density tester (Meta Lab) USP Model no. I and the tapped volume were noted (USP, 2006). The tapped density was calculated by the formula.

 

 

 

Where, ρ₀ = tapped density,

M = weight of powder        and    

V_t= tapped volume of powder in cm³

 

 

 

 

Hausners ratio:

Hausner ratio gives an idea regarding the flow of the blend. It is the ratio of tapped density to the apparent density. Hausners ratio was calculated as

 

 

 

Compressibility index:

The compressibility index measures of the propensity of powder to be compressed. The packing ability of drug was evaluated from change in volume, which is due to rearrangement of packing occurring during tapping (USP, 2006). It is indicated as Carrs compressibility index (CI) and can be calculated as follows:

 

 

 

Angle of repose:

Angle of repose is defined as the maximum angle possible between the surface of pile of powder and horizontal plane. The angle of repose was determined by the funnel method. A glass funnel was secured with its tip at a given height (H) above a piece of graph paper placed on a horizontal surface. Powder was poured through the funnel until the apex of the conical pile touched the tip of the funnel (Lachman et al., 1991). The angle of repose was calculated with the formula.

 

OR

 

Where, θ = is the angle of repose,

h = height of the conical pile  and   r = radius of the conical pile.

 

Evaluation of Clopidogrel bisulfate matrix tablet^[19]

Thickness:

The thickness of tablet was determined using Electronic vernier caliper (Workzone, India). Tablet thickness should be controlled within a ±5% variation of the mean value.

Hardness:

Tablets require a certain amount of strength, or hardness, to withstand the mechanical shocks of handling in manufacturing, packaging as well as in shipping. The hardness of the tablets here was measured using simple Monsanto hardness tester (Cadmach, Ahmadabad, India). In this, a tablet is placed between the plungers, and was tightened from one end, and pressure required to break tablet diametrically was measured. The hardness was measured in terms of kg/cm².

 

Friability:

Tablet strength was tested by Roche friabilator. Pre weighted tablets were allowed for 100 revolutions in 4 minute and dedusted. The percentage weight loss was calculated by reweighing the tablets. The percentage weight loss should not be more than 1% of the total weight. The % friability then calculated by:

 

%

 

Uniformity of weight:

20 units were selected at random and were weighed individually, and average weight was calculated. Not more than 2 of the individual weight of tablets should deviate from the average weight by more than 5%.

 

Disintegration time:

The disintegration time for of  tablet was measured using the disintegrtion test appratus for tablets as described in the Pharmacopoeia. Six Tablets were placed in the disintegration tubes of disintegration appratus (Electrolab) and time required for complete disintegration without leaving any residues on the screen was recorded as disintegration time (Indian Pharmacopoeia, 2007).

 

Content Uniformity:

Weigh and powder 20 tablets. Weigh accurately a quantity of the powder containing about 75 mg of Clopidogrel bisulfate, add 10 ml of methanol sonicate to dissolve and add 50 ml of 6.8 PH PBS shake for 20 minutes and dilute to 100.0 ml with 6.8 PH PBS. Mix, filter, dilute 1.0 ml of the filtrate to 10.0 ml with water and measure the absorbance of the resulting solution at the maximum at about 270 nm. The tablet preparation complies with the test, only if each individual content lies between 90.00 to 110 % of the average content.

 

In –vitro Release Studies for Tablet:

In vitro drug release studies of the prepared matrix tablets were conducted for a period of 12 hours by using an USP Type II (Paddle) Dissolution apparatus (Electrolab TDT 08L, India) at 37± 0.5° C.  The agitation speed was 50 rpm.  The dissolution study was carried out in 900 ml0.1 N hydrochloric acid at 37±     0.5 ºC for first 2 hours and then in 900 ml of phosphate buffer (pH 6.8) up to 10hours. 5 ml of the sample was withdrawn at regular intervals and the same volume of fresh dissolution medium was replaced to maintain the volume constant. The samples withdrawn were filtered through a Whatman filter no.1 and the drug content in each sample was analyzed with UV spectrophotometer. The amount of drug present in the samples were calculated with the help of calibration curve constructed from reference standard.

 

In –vitro Release Studies for Capsules:

In vitro drug release studies of the prepared matrix capsule were conducted for a period of 12 hours by using an USP Type I (Basket) Dissolution apparatus (Electrolab TDT 08L, India) at 37± 0.5° C.  The agitation speed was 50 rpm.  The dissolution study was carried out in 900 ml0.1 N hydrochloric acid at 37±0.5 ºC for first 2 hours and then in 900 ml of phosphate buffer (pH 6.8) up to 10 hours. 5 ml of the sample was withdrawn at regular intervals and the same volume of fresh dissolution medium was replaced to maintain the volume constant. The samples withdrawn were filtered through a Whatman filter no.1 and the drug content in each sample was analyzed with UV spectrophotometer. The amount of drug present in the samples was calculated with the help of calibration curve constructed from reference standard.

 

Comparison of drug release of marketed formulation with Clopidogrel bisulfate tablet:

Clopidogrel bisulfate tablets prepared by direct compression method with the polymer Na-CMC, and Carnuba Wax and were compared with the marketed formulation CLOPITAB-75tablet.

 

Comparison of drug release of marketed formulation with Clopidogrl bisulfate capsule:

Clopidogrel bisulfate capsule prepared with the polymer, Na-CMC, Carnuba Wax and Ethyl cellulose were compared with the marketed formulation Clopitab-75 tablet.

 

Stability Study:^[20]

During stability studies the product is exposed to conditions of temperature and humidity. However the studies will take a longer period of time and hence it would be convenient to carry out accelerated stability studies where the product is stored under extreme condition of temperature and humidity. In the present work, stability studies were carried out on formulation under the following condition for period of 6 month as prescribed by ICH guidelines for accelerated study at 40^oC±2⁰C and relative humidity (RH) of 75%±5%. The formulation were withdrawn after completion of 6 month and analyzed for physical characterization, content uniformity and drug release.

 

RESULT AND DISCUSSION:

Determination of λ_max of Clopidogrel bisulfate in PBS pH 6.8:

Solutions of Clopidogrel bisulfate was prepared in PBS pH 6.8and scanned between 400-200 nm using UV spectrophotometer showed peak at wavelength 270 nm. However, keeping in mind the probable concentrations likely to be encountered while carrying out In-vitro release studies and considering the predicted theoretical λ_max involved, the working λ_max was decided as 270nm as shown in Figure 2.

 

 

Figure 2.UV-Visible spectrum of Clopidogrel bisulfate in PBS pH 6.8

 

Infra-Red Spectrum:

Infra-red spectrum of Clopidogrel bisulfate is shown in Figure 3. The major peaks observed and corresponding functional groups are present. Infra-red spectrum shows peak characteristic of structure of Clopidogrel bisulfate.

 

Figure: 3.FTIR spectrum of Clopidogrel bisulfate

 

 

Evaluation of blend containing Clopidogrel bisulfate and Na-CMC:

Table No.3: Results of pre-compression evaluation of formulation

Sr.No.	Precompression parameters	F1 (1:0.5)	F2  (1:1)	F3  (1:1.5)
1	Bulk density (gm/ml) ±S.D.	0.4532±0.008	0.3954±0.007	0.4167±0.002
2	Tapped density   (gm/ml) ± S.D.	0.4923±0.005	0.4276±0.004	0.4954±0.002
3	Compressibility index % ± S.D.	13.72±0.825	12.08±1.278	11.45±0.305
4	Hausner’s ratio ± S.D.	1.1492±0.012	1.137±0.017	1.123±0.004
5	Angle of repose ( 0 )± S.D.	27.72±0.02	26.85±0.03	26.19±0.01

 

Evaluation of blend containing Clopidogrel bisulfate and Ethyl Cellulose

Table No.4: Results of precompression evaluation of formulation

Sr.No.	Precompression parameters	F4 (1:0.5)	F5  (1:1)	F6  (1:2.5)
1	Bulk density (gm/ml) ±S.D.	0.4176±0.007	0.4232±0.003	0.4005±0.003
2	Tapped density   (gm/ml) ± S.D.	0.4723±0.006	0.4516±0.045	0.4731±0.005
3	Compressibility index % ± S.D.	14.64±1.360	13.5±2.501	14.45±0.140
4	Hausner’s ratio ± S.D.	1.14±0.02	1.15±0.03	1.17±0.003
5	Angle of repose( 0 ) ± S.D.	29.05±0.03	30.31±0.01	28.72±0.02

 

Evaluation of blend containing Clopidogrel bisulfate and Carnuba Wax:

Table No.5: Results of precompression evaluation of formulation

Sr.No.	Precompression parameters	F7 (1:0.5)	F8 (1:1)	F9  (1:1.5)
1	Bulk density (gm/ml) ±S.D.	0.4197±0.004	0.4299±0.004	0.4808±0.003
2	Tapped density   (gm/ml) ± S.D.	0.4808±0.004	0.5021±0.004	0.5126±0.004
3	Compressibility index % ± S.D.	14.75±0.2	14.49±0.195	13.99±0.270
4	Hausner’s ratio ± S.D.	1.171±0.002	1.161±0.004	1.158±0.003
5	Angle of repose( 0 ) ± S.D.	28.07±0.02	26.45±0.03	26.85±0.01

 

Evaluation of post compression parameters:

Evaluation for tablets containing Clopidogrel bisulfate and Na-CMC:

Table No.6: Evaluation of Tablet for F1, F2 and F3

Sr. No.	Parameter	Observation
		F1 (1:0.5)	F2 (1:1)	F3  (1:1.5)
1	Average Weight (mg)±S.D.	169.7±0.4582	172.4±0.5033	175.8±0.4041
2	Weight variation (%)±S.D.	1.616±0.0055	1.25 ±0.0280	1.330±0.020
3	Thickness (mm)±S.D.	4.4±0.5507	4.5±0.2886	4.4±0.4041
4	Hardness (kg/cm2)±S.D.	3±0.2886	3.5±0.5773	4±0.2886
5	Friability (%)±S.D.	1.04±0.0702	0.35±0.07637	0.39±0.0503
6	Content Uniformity (%)±S.D.	92.13±0.8310	93.12±0.2761	91.67 ±0.7261
7	Disintegration Time (Min)±S.D.	10.5±0.2081	11.2±0.2516	10.6±0.2516

 

 

 

Evaluation for Tablets containing Clopidogrel bisulfate and Carnuba Wax:

Table No.7:  Evaluation of Tablet F7, F8 and F9

Sr. No.	Parameter	Observation
		F7 (1:0.5)	F8 (1:1)	F9 (1:1.5)
1	Average Weight (mg)±S.D.	174.30±0.3055	175.69±0.2463	173.88±0.3250
2	Weight variation (%)±S.D.	1.29 ±0.004	1.26±0.0251	1.36±0.0064
3	Thickness (mm)±S.D.	4.5±.2886	3.5±0.7637	4.5±0.5773
4	Hardness (kg/cm2)±S.D.	3.5±0.2886	4±.5	4.5±0.2845
5	Friability (%)±S.D.	0.74±0.0450	0.92±0.0351	0.79±0.2645
6	Content Uniformity (%)±S.D.	88.76 ±0.4570	87.46±0.4118	86.37 ±0.1193
7	Disintegration Time  (Min)±S.D.	7±0.2516	7.5±0.1732	8.5±0.3605

 

 

In Vitro Drug Release Study:

Comparison of drug release of marketed tablet with Clopidogrel bisulfate formulation

Table No.8: Comparison of drug release of marketed formulation with Clopidogrel bisulfate formulation.

Time (hrs)	F1 1:0.5	F2 1:1	F3 1:1.5	F4 1:0.5	F5 1:1	F6 1:1.5	F7 1:0.5	F8 1:1	F9 1:1.5	CLOPI TAB -75
1	7.34	6.09	7.52	7.52	6.09	7.52	7.34	6.09	7.52	35.34
2	15.72	12.26	15.91	15.91	12.26	15.91	12.72	12.26	15.91	43.48
3	28.46	19.49	23.74	23.74	19.49	23.74	24.46	19.49	23.74	54.29
4	36.77	25.98	29.81	29.81	25.98	29.81	36.77	25.98	29.81	70.82
5	42.82	31.54	35.56	35.56	31.54	35.56	42.82	31.54	35.56	83.63
6	51.90	43.89	46.19	46.19	43.89	46.19	49.90	43.89	46.19	92.03
7	59.43	49.31	55.97	55.97	49.31	55.97	55.43	49.31	55.97	92.07
8	65.74	57.34	67.76	67.76	56.34	59.76	62.74	56.34	59.76	92.09
9	72.36	68.75	71.12	71.12	63.75	68.12	66.36	63.75	68.12	92.11
10	83.53	74.87	77.39	77.39	70.87	73.39	72.36	70.87	73.39	92.13
11	87.17	87.47	85.93	85.93	78.47	77.93	79.79	79.47	79.93	92.13
12	91.69	92.59	90.18	90.18	88.59	87.17	86.69	85.59	84.18	92.15

The release pattern for F1, F2, F3, F4, F5, F6, F7, F8 and F9 formulation compared with marketed formulation are shown in Figure 4.

 

 

 

Figure 4:Comparative drug release of Clopidogrel bisulfate formulations with marketed formulation.

 

From the figure it shows that when Clopidogrel bisulfate formulation compared with marketed formulation, the marketed formulation shows 54.2% release in 3 Hr, and initially 35% release within 1 hrs, but when compared with Na-CMC formulation i.e. F2 formulation shows 19.19% drug release in 3 Hr and about 57.3% release in 8 Hr shows steady state release for formulation, F1 and F3 also shows same release pattern as that of F2, F2 was selected as optimum batch as F2 formulation has shown 6.09% drug release within 1hrs and 92.59.% upto 12Hr, F3 formulation has shown only drug release upto 46.19% in 6 hrs, but formulation F2 has shown 40% (Approx40%) drug release within 7 Hr and 92.59% drug release within 12 Hrs. Sustain release is attained with Na-CMC polymer as it shows better release pattern than that of marketed formulation. F7, F8 and F9 shows about 84-86 % drug release in 12 Hrs. Wax act as a retardant material for drug and it retarded the drug upto 12 Hr. For formulation F4, F5 and F6 it shows about 23.7,19.4,23.74% of drug release upto 3 Hr and about 87-90 % of drug release in 12 Hr, but the method adopted for F4, F5 and F6 was microencapsulation, there is increase in the concentration of polymer, the release decreases.

 

 

Comparison of drug release of marketed formulation with Clopidogrel bisulfate capsule:

Table No.9:Comparison of drug release of marketed formulation with Clopidogrel bisulfate capsule:

Time Hrs	F10 (1:0.5)	F11 (1:1)	F12 (1:1.5)	F13 (1:0.5)	F14 (1:1)	F15 (1:1.5)	MARKETD (CLOPITAB-75)
1	6.34	6.09	7.52	7.34	6.09	7.52	35.34
2	10.72	12.26	15.91	12.72	12.26	14.91	43.48
3	18.46	17.49	20.74	20.46	19.49	18.74	54.29
4	26.77	25.98	29.81	26.77	25.98	29.81	70.82
5	37.82	35.54	35.56	38.82	33.54	35.56	83.63
6	49.90	47.89	46.19	49.90	53.89	56.19	92.03
7	55.43	56.31	55.97	58.43	69.31	65.97	92.03
8	69.13	68.34	60.76	71.74	76.34	79.76	92.03
9	80.14	83.75	79.12	87.36	83.75	85.12	92.03
10	92.14	93.15	92.50	90.91	92.10	91.30	92.03
11	-	-	-	-	-	-	92.03
12	-	-	-	-	-	-	92.03

 

 

The release pattern for F10, F11, F12, F13, F14 and F15 formulation compared with marketed formulation are shown in Figure 5.

 

Clopidogrel bisulfate capsules containing drug with Na-CMC and Carnuba wax (F10, F11, F12, F13, F14 and F15) when compared with marketed tablet, 19-20% drug release was found within 3 hrs. For F10, F11 and F12 formulations19-20% drug release was found .Marketed formulation has shown 54.29% drug release within 3 hrs. F13, F14 and F15 formulation shows about 19-20% drug release within 3 hrs period. This indicates that Na-CMC shows sustained release in physical mixture form. Drug-physical mixture with carnuba wax does not show sustained property.

 

For capsules greater drug release was found up to 10 hrs .90-92%, as no compression force was applied to bulk material filled in it. When such bulk mass was processed for compression, the drug was in the form of matrix and causes the retardation of drug in dissolution medium.

 

Similarity Factor (f2) and Difference Factor (f1) study:

Clopidogrel bisulfate formulations were compared with the marketed formulation CLOPITAB-75 tablet. FDA and the European Agency for the Evaluation of Medicinal Product, suggest that two dissolution profiles are declared similar if f₂valueis between 50 and 100 and f₁ value is between 0 to15.Results are shown in Table No.10

 

 

Table No. 10: f 1 and f 2 values for all formulations

Sr. No.	Batch Code	Difference factor f1	Similarity factor f2
1	F1	71	36
2	F2	79	24
3	F3	69	40
4	F4	63	37
5	F5	57	42
6	F6	51	46
7	F7	38	53
8	F8	43	51
9	F9	39	54
10	F10	60	49
11	F11	65	51
12	F12	64	47
13	F13	38	53
14	F14	44	50
15	F15	41	56

 

From the above data it can concluded that formulations containing Carnauba Wax i.e. F7, F8, F9, F13, F14, and F15 show relatively similar result as that marketed tablet. They show same drug release as that of marketed drug release. But other formulations differ from marketed formulation it shows that different release profile was found as compared to marketed formulation.

 

Stability study:

The stability study for formulation F2 was conducted at 40±2⁰ C, 75±2% RH. The drug content and In-vitro dissolution study calculated after 6 month.

 

Figure 5: Comparative drug release of Clopidogrel bisulfate formulations with marketed formulation.

 

 

Figure 6: Comparison of dissolution profile of optimize batch during stability study

 

 

Table No.11:Comparison of % CDR for stability study

Time (hrs)	% CDR
	Before Stability Study	After 90 Days
1	6.09	5.08
2	12.26	11.25
3	19.49	19.48
4	25.98	24.98
5	31.54	30.53
6	43.89	42.89
7	49.31	48.29
8	57.34	56.32
9	68.75	67.70
10	74.87	72.46
11	87.47	86.40
12	92.5	91.55

 

Table No.12: Stability study of Clopidogrel bisulfate formulation

Time (hrs)	Drug content
	Before Stability Study	After Stability Study
1	93.12±0.27	91.47±0.72

 

Physical appearance of stored tablet and capsule were found to be stable without any colour change and appearance.

 

Results of stability studies showed that there is no significant change in content uniformity and drug release for optimized formulation after elevated temperature and humidity conditions during stability studies. Thus it can be proved from the stability studies that the prepared formulation is stable and not affected by humidity and temperature conditions.

 

Model Fitting For Batches of Clopidogrel bisulfate Formulations:

It is shown in Table No.13the model fitting for the Clopidogrel bisulfate tablet formulations. These models are done with the help of PCP Disso Software; all R²values are given in table No. 13.

Table No. 13: Model fitting for batches of Clopidogrel bisulfate formulations

Clopidogrel bisulfate  Batches	Zero Order	First Order	Higuchi	Hixson Crowell	Korsmeyer-Peppas
	R2	R2	R2	R2	R2	n-value
F1	0.88	0.82	0.94	0.81	0.98	0.98
F2	0.89	0.93	0.92	0.89	0.99	1.04
F3	0.86	0.92	0.91	0.88	0.97	1.01
F4	0.89	0.91	0.90	0.88	0.96	0.97
F5	0.87	0.90	0.89	0.87	0.97	0.98
F6	0.86	0.89	0.86	0.83	0.98	1.02
F7	0.88	0.88	0.91	0.87	0.99	0.97
F8	0.88	0.87	0.88	0.86	0.94	0.96
F9	0.82	0.89	0.81	0.79	0.97	0.98
F10	0.86	0.90	0.84	0.81	0.96	1.0
F11	0.83	0.93	0.83	0.84	0.93	0.96
F12	0.82	0.92	0.88	0.87	0.97	1.1
F13	0.84	0.91	0.89	0.88	0.96	0.97
F14	0.85	0.90	0.86	0.84	0.98	1.01
F15	0.89	0.7211	0.91	0.87	0.95	1.07

 

From the above table it is seen that the best fit model for formulation is Korsmeyer-Peppas, such type of model is

 

applicable when multiple dissolution mechanism are seen.

CONCLUSION:

In conclusion, the results of the present study indicate that the release of a hydrophilic drug from a matrix tablet formulation is primarily affected by the ratio and the type of the polymer and secondarily by the direct compression method. Clopidogrel bisulfate sustain release tablet can be formulated with the help of Na-CMC as it shows better result than that of Carnuba wax, as Na-CMC shows better sustain action of drug than Carnuba wax. Clopidogrel bisulfate formulation compared with marketed formulation, the marketed formulation shows 90% release in 6Hr, and initially 35% drug release within 1hrs, but when compared with Na-CMC formulation i.e. F2 (Drug:Na-CMC 1:1) formulation shows 25.98% drug release in 4 Hr and about 92.59% release in 12 hrs it shows steady state release for formulation.F2 was selected as optimum batch, F2 has shown about 50%  drug release within 7 Hr and 74.87% drug release within 10 Hrs.

 

For capsules greater drug release was found as no compression force was applied to bulk material filled in it. When such bulk mass was processed for compression the drug was in the form of matrix and causes the retardation of drug in dissolution medium.

 

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Received on 06.07.2016       Accepted on 19.08.2016     

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