FORMULATION AND CHARACTERIZATION OF SR MATRIX OF ENDOTHELIN RECEPTOR ANTAGONIST OF BOSENTAN BY VARIOUS NATURAL POLYMERS

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1 Page3984 Indo American Journal of Pharmaceutical Research, 2014 ISSN NO: FORMULATION AND CHARACTERIZATION OF SR MATRIX OF ENDOTHELIN RECEPTOR ANTAGONIST OF BOSENTAN BY VARIOUS NATURAL POLYMERS Y.Ganesh Kumar* 1, J.Sreekanth 2, D.Satyavati 1 1, Sree Dattha Institute of Pharmacy, Sheriguda, Ibrahimpatnam, R.R Dist, TS, India. 2 R&D, MSN Laboratories Pvt. Ltd, Hyderabad, TS, India. ARTICLE INFO Article history Received 07/10/2014 Available online 30/10/2014 Keywords Endothelin Receptor Antagonist (ERA), Pulmonary Arterial Hypertension (PAH), Bosentan, Wet Granulation Method, Pectin, SR Matrix. ABSTRACT The Present investigation an attempt has been made to increase therapeutic efficacy, reduce frequency of administration and improve patient compliance, by developing SR Matrix tablets of Bosentan is an Endothelin Receptor Antagonist (ERA) indicated for the treatment of Pulmonary Arterial Hypertension (PAH). Bosentan Sustained Release Matrix Tablets were prepared by using different natural polymers like Xanthan gum, Guar gum, Pectin at different ratios of Drug: Polymer. The Matrix tablets were prepared by Wet granulation method. The prepared tablets were selected for DSC and FTIR studies. The tablets were selected for DSC and FTIR studies did not show any chemical interaction between drug and polymer. The prepared tablets were evaluated for various Physico chemical parameters. Invitro drug release study was carried out in simulated gastric fluid (0.1N Hcl) for the first 2 hours and in Phosphate buffer (P H 6.8) for the next 10 hours following USP Paddle method. The release kinetics was analyzed using the Zero-order, first order model equation, Higuchi s- square root equation, and Korsmeyer-Peppas model. Among the all formulations, F7 formulation containing Drug to Pectin in ratio 1:0.5 is optimized based on its ability to sustain drug release till 12 hrs of dissolution study. The Optimized formulation F7 showed zero order release with fairly linear as indicated by their high regression values (R 2 = ). Results revealed that F7 formulation follows the zero order transport mechanism. Corresponding author Y.Ganesh Kumar M.Pharm.,(Ph.D) Department of Pharmaceutics. Sree Dattha Institute of Pharmacy, Sheriguda, Ibrahimpatnam, R.R Dist, TS, India ganesh.yed@gmail.com Please cite this article in press as Y.Ganesh Kumar, et al. Formulation and Characterization of Sr Matrix of Endothelin Receptor Antagonist of Bosentan By Various Natural Polymers. Indo American Journal of Pharm Research.2014:4(10). Copy right 2014 This is an Open Access article distributed under the terms of the Indo American journal of Pharmaceutical Research, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

2 Page3985 INTRODUCTION Oral drug delivery is the most widely utilized route of administration among all the routes that have been explored for the systemic delivery of drug via pharmaceutical products of different dosage form. Oral route is considered most natural, uncomplicated, convenient and safe due to its ease of administration, patient acceptance, and cost effective manufacturing process. The goal of a sustained release dosage form is to maintain therapeutic blood or tissue levels of the drug for an extended and specified period of time. This is generally accomplished by attempting to obtain "zero-order" release from the dosage form. Zero-order release constitutes drug release from the dosage form which is independent of the amount of drug in the delivery system (i.e. a constant release rate). Sustained-release systems generally do not attain this type of release and usually try to mimic zero-order release by providing drug in a slow first-order fashion (i.e., concentration release dependent). Systems that are designated as prolonged release can also be considered as attempts at achieving sustained-release delivery [1, 2]. There are many definitions of sustained release but the simplest definition is Any drug or dosage form or medication that prolongs the therapeutic activity of drug. The overall objective is that, once the drug-carrier material has been injected or otherwise implanted or taken orally into the body, the drug is released at a predetermined rate for some desired period of time. Bosentan is a endothelin receptor antagonist used in the treatment of Pulmonary artery hypertension (PAH).It is readily absorbed from the gastrointestinal tract with oral bioavailability of about 50% and a plasma elimination half-life is 5 hours. MATERIALS AND METHODS Materials: Bosentan was provided by MSN Laboratories Pvt.Ltd, Hyderabad, Natural polymers was procured from Yarrow chem. Products, Mumbai, PVP- K 30, Talc, Magnesium stearate, and MCC was bought from Signet Chem., Mumbai. METHODOLOGY: Preformulation Studies: Standardization of Bosentan by UV-Visible Spectrophotometry in 0.1 N Hcl Solutions: Preparation of stock solution: Stock solution 100µg/ml of Bosentan was prepared in 0.1N Hcl solution. This solution was approximately diluted with 0.1N Hcl to obtain a concentration of 10µg/ml. The resultant solution was scanned in range of nm using UV double beam spectrophotometer (Lab India UV-3000+). Standard calibration of Bosentan in 0.1N Hcl: 100mg of Bosentan was accurately weighed and dissolved in100ml of 0.1N Hcl to obtain a concentration of 1000µg/ml. From the above 10ml was withdrawn and diluted to 100ml to obtain a concentration of 100µg/ml. From this stock solution aliquots of 0.5ml, 1ml, 1.5ml, 2ml and 2.5ml were diluted in 10ml volumetric flask with phosphate buffer to give concentrations in range of 10µg/ml to 70µg/ml respectively, absorbance was measured at 242 nm. Standardization of Bosentan by UV-Visible Spectrophotometry in p H 6.8 Solutions: Preparation of stock solution: Stock solution 100µg/ml of Bosentan was prepared in phosphate buffer of ph 6.8. This solution was approximately diluted with phosphate buffer of ph 6.8 to obtain a concentration of 10µg/ml. The resultant solution was scanned in range of nm using UV double beam spectrophotometer (Lab India UV-3000+). Standard calibration of Bosentan in phosphate buffer of p H 6.8: 100mg of Bosentan was accurately weighed and dissolved in 100ml of ph 6.8 phosphate buffer to obtain a concentration of 1000µg/ml. From the above 10ml was withdrawn and diluted to 100ml to obtain a concentration of 100µg/ml. From this stock solution aliquots of 0.5ml, 1ml, 1.5ml, 2ml and 2.5ml were diluted in 10ml volumetric flask with phosphate buffer to give concentrations in range of 5µg/ml to 20µg/ml respectively, absorbance was measured at 243 nm. Drug- Excipient Compatibility by FTIR studies: In the preparation of Sustained Release tablet, drug and polymer may interact as they are in close contact with each other, which could lead to instability of drug. Preformulation studies regarding drug-polymer interactions are therefore very critical in selecting appropriate polymers. FT-IR spectroscopy (Agilent) was employed to ascertain the compatibility between bosentan and selected polymers. The individual drug and drug with excipients were scanned separately. Procedure: Potassium bromide was mixed with drug and polymer in the ratio of 100:1 and pellet was prepared using KBr pellet press and spectrum was taken using FTIR (Agilent). FT-IR spectrum of bosentan was compared with spectrum of bosentan and polymer. Disappearance of bosentan peaks or shifting of peak in any of the spectra was studied [3-6].

3 Page3986 Angle of repose: The angle of repose of blends was determined by the funnel method. The accurately weighed blend was taken in funnel. The height of the funnel was adjusted in such a way that the tip of the funnel just touched the apex of the heap of the blend. The blend was allowed to flow from the funnel on the surface. The diameter and height of the heap formed from the blend was measured. The angle of repose was calculated using following formula [7]. Tan Ѳ= h/r Where, h is height of the heap and r is the radius of the heap of granules. Carr s compressibility index: The Carr s compressibility Index was calculated from Bulk density and tapped density of the blend. A quantity of 2g of blend from each formulation, filled into a 10ml of measuring cylinder. Initial bulk volume was measured, and cylinder was allowed to tap from the height of 2.5cm. The tapped frequency was 25±2 per min to measure the tapped volume of the blend. The bulk density and tapped density were calculated by using the bulk volume and tapped volume. Carr s compressibility index was calculated by using following formula [8,9]. Carr s compressibility index (%) = [(Tapped density-bulk density) X100]/Tapped density Bulk Density (BD): An accurately weighed powder blend from each formula was lightly shaken to break any agglomerates formed and it was introduced in to a measuring cylinder. The volume occupied by the powder was measured which gave bulk volume. The bulk densities (BD) of powder blends were determined using the following formula [10-13]. Bulk density = Total weight of powder / Total volume of powder Tapped bulk density (TBD): An accurately weighed powder blend from each formula was lightly shaken to break any agglomerates formed and it was introduced into a measuring cylinder. The measuring cylinder was tapped until no further change in volume was noted which gave the tapped volume. The tapped bulk densities (TBD) of powder blends were determined using the following formula TBD= Total weight of powder / Total volume of tapped powder Evaluation of tablets The weight of tablets was evaluated on 20 tablets using an electronic balance. Friability was determined using 6 tablets in Roche friability tester at 25rpm. Hardness of the tablets was evaluated using a Monsanto hardness tester [14-17].The hardness of all the formulation was between 4-5 kg /cm 2. Table 1: Composition of Bosentan: S.no Ingredients F1 F2 F3 F4 F5 F6 F7 F8 F9 1 Bosentan Xanthan gum Guar gum Pectin PVP-K 30 (5%) QS QS QS QS QS QS QS QS QS 6 Talc Mg.Stearate MCC Total Weight Preparation of tablets: Wet granulation method: All the powders were passed through 80 mesh. Required quantities of all ingredients were mixed thoroughly and a sufficient volume of granulating agent was added slowly. After enough cohesiveness was obtained, the mass was sieved through 22/44 mesh. The granules were dried at 40 C for 12hrs. Once, dry the granules retained on 44 mesh were mixed with 10% of fine granules that passed through 44 mesh. Talc and magnesium stearate were added as glidant and lubricant [15]. In all formulations, the amount of the active ingredient is equivalent to 62.5 mg of Bosentan (Table 1) In vitro dissolution studies: In vitro drug release studies from the prepared matrix tablets were conducted using USP type II apparatus at 37 0 C ±0.5 0 C at 50rpm. Dissolution mediums used were 900mL of 0.1N HCl and phosphate buffer of ph 6.8. The release rates from SR matrix tablets were conducted in HCl solution (ph 1.2) for 2 hrs and changed to phosphate buffer (ph 6.8) for further time periods. The samples were withdrawn at desired time periods from dissolution media and the same were replaced with fresh dissolution media of respective P H. The samples were analyzed by UV-Visible Spectrophotometer (Lab India 3000+). The amounts of drug present in the samples

4 Page3987 were calculated with the help of appropriate calibration curves constructed from reference standards. Drug dissolved at specified time periods was plotted as percent release versus time curve [16]. Dependent-model method (Data analysis): In order to describe the Bosentan release kinetics from individual tablet formulations, the corresponding dissolution data were fitted in various kinetic dissolution models: zero order, first order, Higuchi, Korsmeyer Peppas. When these models are used and analyzed in the preparation, the rate constant obtained from these models is an apparent rate constant. The release of drugs from the matrix tablets can be analysed by release kinetic theories. To study the kinetics of drug release from matrix system, the release data were fitted into Zero order as cumulative amount of drug release vs. time (Eqn.3), first order as log cumulative percentage of drug remaining vs. time (Eqn.4), Higuchi model as cumulative percent drug release vs. square root of time (Eqn.5). To describe the release behavior from the polymeric systems, data were fitted according to well known exponential Korsmeyer Peppas equation as log cumulative percent drug release Vs log of time equation [17-19]. (Eqn.6). (i) Zero order kinetics: Qt=K0t Eqn.(3) Where, Q= Amount of drug release in time t K0 = Zero order rate constant expressed in unit of concentration /time t = Release time (ii) First order kinetics: Log Q=Log Q0-kt/2.303 Eqn.(4) Where, Q0= is the initial concentration of drug k= is the first order rate constant t =release time (iii) Higuchi kinetics: Q=kt1/2 Eqn.(5) Where, k= Release rate constant t=release time, Hence the release rate is proportional to the reciprocal of the square root of time. (iv) Korsmeyer-Peppas: First 60% in vitro release data was fitted in equation of Korsmeyer et al. to determine the release behavior from controlled release polymer matrix system. The equation is also called as power law, Mt /M =Kt n Eqn.(6) Where, Mt = amount of drug released at time t M = amount of drug released after infinite time Mt /M = fraction solute release t = release time K = kinetic constant incorporating structural and geometric characteristics of the polymer system n = diffusional exponent that characterizes the mechanism of the release of traces. The magnitude of the release exponent n indicates the release mechanism (i.e. Fickian diffusion, Non Fickian, supercase II release). For matrix tablets, values of n of near 0.5 indicates Fickian diffusion controlled drug release, and an n value of near 1.0 indicates erosion or relaxational control (case II relaxational release transport, non Fickian, zero order release). Values of n between 0.5 and 1 regarded as an indicator of both diffusion and erosion as overall release mechanism commonly called as anomalous release mechanism. RESULTS AND DISCUSSION Preformulation characteristics: [20-23] The drug Bosentan was standardized by UV method in 0.1N Hcl and ph 6.8 Buffer separately. The lambda max were 242 nm and 243 nm in 0.1N Hcl and ph 6.8 buffer respectively and the linearity range was 5-70 mcg/ml in both the media.

5 Page3988 Figure 1: λ max of Bosentan in 0.1 N HCl (242 nm). Table 2: Absorbences of Bosentan in 0.1N HCL. S.No Concentration(mcg/ml) Absorbance(nm) Figure 2: Calibration curve of Bosentan in 0.1N HCL Figure 3: λ max of Bosentan in ph 6.8 Buffer (243nm).

6 Page3989 Table 3: Absorbences of Bosentan in 6.8 ph Phosphate buffer. S.No Concentration(mcg/ml) Absorbance (nm) Figure 4: Calibration curve of Bosentan in 6.8 ph Phosphate buffer. Drug Excipient Compatibility Studies- FTIR: Drug-Excipient compatibility studies by FTIR revealed no interaction between drug and the polymers used in the formulation thus showing compatibility. Figure 5: FTIR spectra of Bosentan pure Drug. Figure 6: FTIR spectra of Bosentan pure Drug + Pectin.

7 Page3990 Figure 7: FTIR spectra of Optimized Formulation (Bosentan+Pectin+PVP-K 30+Talc+Mg.Stearate+MCC). Differential Scanning Calorimetry (DSC): The compatibility and interactions between drugs and polymer were checked using differential scanning calorimetry (DSC). Any possible drug polymer interaction can be studied by thermal analysis. The DSC study was performed on pure drug (Bosentan) and Optimized Formulations (drug + Pectin+ pvp k 30 + talc + Mg.Stearate + Mcc). The study was carried out using Hitachi The 2 mg of sample were heated in a hermetically sealed aluminum pans in the temperature range of ºc at heating rate of 10ºc /min under nitrogen flow of 40ml/min. Finally hence their no interaction was found between drug and the polymers. Figure.8 Differential Scanning Calorimetry analysis of Bosentan Pure Drug. Figure.9 Differential Scanning Calorimetry analysis of Optimized Formulation (Drug+Pectin+pvp k 30+talc+Mg.Stearate+Mcc). Physical characteristics of blends and tablets:

8 Page3991 The blends of different formulations were evaluated for angle of repose, Carr s compressibility index etc., The results of Carr s compressibility Index (%) and Angle of repose ranged from and respectively which showed that blends from all the formulations having good flow property. The hardness and percentage friability ranged from 4-5kg/cm 2 and % respectively. Table 4: Pre compression parameters: Formulation Bulk density Tapped density Hausner s Carr s Compressibility Angle of repose (Ө) code (gr/cm 3 ) (gr/cm 3 ) ratio Index (%) F ± ± ' F ± ± ' F ± ± ' F ± ± ' F ± ± '33 F ± ± ' F ± ± ' F ± ± ' F ± ± ' All the values are expressed as mean ± S.D. (n = 3) Table 5: Post compression parameters: Formulation code Hardness Friability Weight variation Thickness Drug Content Ӝ (%) (kg/cm 2 ) (%) (mg) (mm) F1 4.3± ± ± ± ±0.76 F2 4.7± ± ± ± ±0.57 F3 4.1± ± ± ± ±0.98 F4 4.9± ± ± ± ±0.35 F5 4.4± ± ± ± ±0.55 F6 4.6± ± ± ± ±0.63 F7 4.7± ± ± ± ±0.44 F8 4.9± ± ± ± ±0.78 F9 4.9± ± ± ± ±0.33 All the values are expressed as mean ± S.D. n = 6, n =10, n = 20, n = 6, Ӝ n = 2. In vitro dissolution studies: Bosentan sustained release tablets were prepared by using different natural polymers. The release profiles of Bosentan sustained release tablets were plotted as Fig The release rate of Bosentan mainly controlled by the hydration and swelling properties of natural polymers which forms a gel layer that controls the water penetration and drug diffusion. The effect of polymer concentration on drug release could be clearly seen from the variation of the dissolution profiles. Among all the formulations (F-1 to F-9) Contained Bosentan and Xanthan gum, Guar gum and Pectin Polymers in different ratios. It was found that drug release of among all the formulations, F-7 containing Pectin in ratio of 1: 0.5 could retard drug for relatively 12 hrs compared to all other formulations. So Formulation F7 has showed maximum amount of drug released with drug release of 98.4±0.18 % in 12 hours, so it will be Optimized formulation. Table 6: Dissolution release profiles of Formulations (F1-F5). % CUMULATIVE DRUG RELEASE S.no Time(hours) F1 F2 F3 F4 F ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±0.51

9 Page ± ± ± ± ±0.21 The data are presented as mean value ± S.D. (n = 3) Table 7: Dissolution release profiles of Formulations (F6-F9). % CUMULATIVE DRUG RELEASE S.no Time(hours) F6 F7 F8 F ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±0.17 The data are presented as mean value ± S.D. (n = 3) Figure.10: Dissolution profiles of Formulations F1-F3 (Using Xanthan gum). Figure.11: Dissolution profiles of Formulations F4-F6 (Using Guar gum).

10 Page3993 Figure. 12: Dissolution profiles of Formulations F7-F9 (Using Pectin). Kinetics of In-vitro Drug Release: The drug diffusion through most type of polymeric system is often best described by Fickian diffusion (diffusion exponent, n=0.5), but other process in addition to diffusion are important. There is also a relaxation of the polymer chain, which influences the drug release mechanism. This process is described as non- fickian or anomalous diffusion (n= ). Release from initially dry, hydrophilic glassy polymer that swell when added to water and become rubbery, show anomalous diffusion as a result of the rearrangement of macromolecular chain. The thermodynamics state of the polymer and penetrate concentration are responsible for the different type of the diffusion. A third class of diffusion is case-ii diffusion (n=1), which is a special case of non- Fickian diffusion. In vitro release data were fitted into various kinetics models like First order, Zero order, Higuchi and Korsmeyer Peppas. The Results are shown in table 8 and graphs in figure 13 to16 of optimized formulation F7.The Optimized formulation F7 showed zero order release with fairly linear as indicated by their high regression values (R 2 =0.9928). Results revealed that F7 formulation follows the zero order transport mechanism. Table 8: Mechanisms of in vitro drug release kinetics studies. Model Formulations R 2 F1 F2 F3 F4 F5 F6 F7 F8 F9 Zero order First order Korsmeyer & r Peppas n Higuchi s Release Kinetics of Optimized formulation F7: Figure.13: Zero order release kinetics of optimized formulation F7.

11 Page3994 Figure.14: First order release kinetics of optimized formulation F7. Figure.15: Higuchi model release kinetics of optimized formulation F7. Figure.16: Peppas model release kinetics of optimized formulation F7.

12 Page3995 CONCLUSION The present study was undertaken with an aim to formulate and evaluate the Bosentan sustained release matrix tablets by using different polymers. Preformulation study was done initially and results directed for the further course of formulation. Based on Preformulation studies different Batches of Bosentan were prepared by using selected excipients. Granules were evaluated for Bulk density, tapped density, compressibility index, Porosity, Angle of repose, Hausner s ratio before being punched as tablets. Various formulations of sustained release matrix tablets of Bosentan were formulated using various polymers viz, Xanthan gum, Guar gum, Pectin in different ratio by wet granulation technique. The tablets were evaluated for physical characterization, in vitro release study. Observation of all formulations for physical characterization had shown that, all of them comply with the Specifications of official pharmacopoeias and/or standard references. Results of in vitro release profile indicated that among all the formulations, F7 was the most promising formulation as it showed that 98.4±0.18 % drug release within 12 hrs and all the physical parameters and release profile was according to the specification, The in vitro release data was plotted for various Kinetic models. The R 2 value for Optimized formulation F7 for Zero order was found to be Finally it was concluded that formulation F7 is an ideal or optimized formulation for 12 hours release as it fulfills all the requirements for sustained release tablets. ACKNOWLEDGEMENTS: The author would like to sincerely gratitude to the MSN Laboratories Pvt. Ltd, Hyderabad, for providing all requirements for this Research work. I am also thankful to Yarrow Chem Products, Mumbai, for providing drugs and Polymers. REFERENCES 1. Chein YW. Noval Drug Delivery Systems. 2 nd edn., Marcel Dekker, New York, 1992, Bankar G.S. and Rhodes C.T. Eds. Modern Pharmaceutics. 3 rd edn., Marcel Dekker, Inc. New York, 1996, Badola Ashutosh,Chakraborthy GS., Formulation and Evaluation of Sustained Release matrix tablets of Antihypertensive drugs using Hydrophobic and Hydrophilic matrix polymers., International Journal of pharmaceutical Erudition.,2014,4(1), Siva Praveen Gutti,Mohini Kalra., Formulation and Evaluation of Sustained Release matrix tablets of Carvedilol, International Research Journal of pharmaceutical and Applied Sciences.,2012,2(4), Bhupendra G.Prajapati, Patel krunal R.,Design and invitro Evaluation of Novel Nicorandil Sustained Release matrix tablets based on combination of Hydrophilic and Hydrophobic matrix system., International Journal of pharmaceutical Sciences Review and Research.,2010,1(1), Afrasim moin,hg. Shiva kumar., Formulation of Sustained Release Diltiazem matrix tablets using Hydrophilic Gum Blends, Tropical Journal of pharmaceutical Research.,2010, 9(3), S.Shanmugam, Ramya Chakrahari, K.Sundaramoorthy, T.Ayyappan, T.Vetrichelvan, Formulation and Evaluation of Sustained Release matrix tablets of Losartan Potassium, International Journal of Pharm Tech Research., 2011, 3(1), Antesh K Jha,Bhattacharya A,Pankaj Verma., Formulation and Invitro Evaluation of Sustained Release matrix tablets of Metoprolol Succinate using Hydrophilic polymer, International Journal of Pharm Tech Research.,2009,1(4), Seppo Pohja,Eero Suihko,Mika Vidgren,Petteri paronen, Jarkko ketolainen.,starch acetate as a tablet matrix for sustained drug release.,journal of Controlled release.,2004,94, Ziad Hussein,Michael Friedman.,Effect of Simulated gastrointestinal changes on the invitro release of Theophylline from novel sustained release matrix tablets with a protein carrier., Journal of Controlled release.,1992,18, Sayed I. Abdel Rahman, Gamal M. Mahrous, Mahmoud Et-Badry., Preparation and Comparative evaluation of sustained release Metoclopramide Hcl matrix tablets., Saudi Pharmaceutical Journal.,2009,17, A. Anil Kumar, M. Sujatha kumari, K. Surekha, ChSS. Prasad and S. Suresh., Formulation and Evaluation of Sustained Release Valsartan matrix tablets by using natural polymers., international journal of pharmaceutical, chemical and biological sciences. 2012, 2(2), Ashtamkar Joel, NangudeShantaram and ChughNaresh., Formulation and Evaluation of Controlled Release Tablets of Labetalol Hydrochloride Using Hydrophobic Polymers, International Journal of Research in Pharmaceutical and Biomedical Sciences,2013,4(1), Prakash B. Mote, Pavan K. Rawat, Shailendra K Singh, Nityanand S. Zadbuke, Amarjit A. Salunke, Vivek B. Rajendra., Formulation and Evaluation of Sustained Release Matrix Tablets of Anti-Asthmatic agent using various polymers,journal of Drug Delivery & Therapeutics; 2013, 3(2), Chinam NP, Arethi BK, Hemant KP, Prakash S, Vimala DM. Design and evaluation of Sustained release bilayer tablets of propranolol hydrochloride. Acta Pharm 2007, 57, P Sivannarayana, A Prameela Rani, V Saikishore., Formulation and Evaluation of Ramipril SR Matrix Tablets by Using Tamrindus Kernal Mucilage as Release Retardent. Research Journal of Pharmaceutical, Biological and Chemical Sciences, 2013, 4(3), Paul WSH, Celine VL, Lai WC, et al. Evaluation of sodium alginate as drug release Modifier in matrix tablets. International Journal of Pharmaceutics. 2006, 309, Mura P, Carla SL, Teresa MF, Mercedes FA, et al.,development of sustained release matrix tablets of didanosine containing methacrylic and ethylcellulose polymers. International Journal of Pharmaceutics. 2002, 234, Gil EC, Colarte AI, Bernard B, et al. Development and optimization of a novel sustained-release dextran tablet Formulation for propranolol hydrochloride. International Journal of Pharmaceutics. 2006, 317,

13 Page Fassihi R, Missaghi S., Release characterization of dimenhydrinate from an eroding and swelling matrix: selection of appropriate dissolution apparatus. International Journal of Pharmaceutics. 2005, 293, Bharat W. Tekade, Yogita A. Chaudhari., Gums and Mucilages: Excipients for modified Drug Delivery System. Journal of Advanced Pharmacy Education & Research.2013, 3 (4), Tetsuo H, Hideyoshi K, Minoru O, et al. Formulation study and drug release mechanism of a new theophylline sustained-release preparation. International Journal of Pharmaceutics.2005, 304, KatzhendlerI., Azoury R., Friedman M., Crystalline properties of carbamazepine sustained Release hydrophilic matrix tablets based on hydroxypropyl methylcellulose, J. of Control Rele; 1998, 54,