International Journal of Innovative Pharmaceutical Sciences and Research

Transcription

1 International Journal of Innovative Pharmaceutical Sciences and Research ENHANCEMENT OF SOLUBILITY OF RITONAVIR BY USING SOLID DISPERSION TECHNIQUE 1 K.Sai Saran*, 2 M.Srujan Kumar, 3 Dr.K.V.Subrahmanyam 1 M.Pharmacy Scholar, Samskruti College of Pharmacy, Hyderabad, INDIA. 2 Faculty, Samskruti College of Pharmacy, Hyderabad, INDIA. 3 Principal, Samskruti College of Pharmacy, Hyderabad, INDIA. Abstract Ritonavir is an antiretroviral drug characterized by low solubility and high permeability which corresponds to BCS class II drug. The purpose of the study was to develop solid dispersion by different methods and investigate them for in vitro and in vivo performance for enhancing dissolution and solubility. The solid dispersion was prepared using PEG 6000, Crosspovidone, sorbitol, mannitol as carriers in different ratios by different methods and was characterized for FT-IR. In vitro dissolution studies were performed in 0.1 N HCl and biorelevant media showed enhanced dissolution rate as compared to marketed formulation. The dissolution of prepared formulation (F10) was relatively higher (96%) than marketed formulation. On the basis of the result obtained, it was concluded that solid dispersion is a good approach to enhance solubility of poorly water-soluble ritonavir. Key words: Ritonavir, solid dispersion, PEG 6000, crospovidone, sorbitol. Corresponding Author: K. Sai Saran /10/1/A,B1,first floor Mahesh nagar colony, gudimalkapur Mehdipatnam saisaran.karnaty@gmail.com Available online: October Issue 266

2 INTRODUCTION The solubility of drug remains one of the most challenging aspects in formulation and development. From literature survey it can be revealed that almost 40 % of all new chemical entities suffer from poor aqueous solubility and hence suffer from poor absorption and bioavailability problems. It is generally recognized that low solubility or poor dissolution often become a rate limiting step in absorption of poorly water soluble drug from gastro intestinal tract and compromise oral bioavailability. Of the several approaches to improve solubility of poorly water soluble drug, solid dispersion technique is widely used to improve the water solubility and in turn dissolution of poorly water soluble drug. Aqueous solubility of any therapeutically active substance is a key property; it governs dissolution, absorption and thus the even in vivo efficacy. To improve the dissolution and bioavailability of poorly water-soluble drugs, researchers have employed various techniques Chio and Serajuadin used the solid-dispersion technique for dissolution enhancement of poorly water-soluble drugs. Being a BCS Class II drug, it often shows dissolution rate-limited oral absorption and high variability in pharmacological effects. The half life of ritonavir is 3-5 hrs. Therefore improvement in its solubility and dissolution rate may lead to enhancement in bioavailability. The aim of the present study was to improve the solubility and dissolution rate of a poorly water soluble drug, ritonavir by solid dispersion technique. The term solid dispersion refers to a group of solid products consisting of at least two different components generally a hydrophilic matrix and a hydrophobic drug. The matrix can be either crystalline or amorphous. The drug can be dispersed molecularly, in amorphous particles (clusters) or in crystalline particles. Chiou and Riegelman defined solid dispersions as the dispersion of one or more active ingredients in an inert excipient or matrix, where the active ingredients could exist in finely crystalline, solubilized, or amorphous states [1]. Sekiguchi and Obi in 1961 first developed the concept of solid dispersion to enhance absorption of poorly water-soluble drugs. It involved the formation of eutectic mixtures of drugs with water-soluble carriers by melting of their physical mixtures, and once the carriers dissolved, the drug precipitated in a finely divided state in water. Later, Goldberg et al. demonstrated that a certain Available online: October Issue 267

3 fraction of the drug might also be molecularly dispersed in the matrix, forming solid solutions, while other investigators reported that the drug might be embedded in the matrix as amorphous materials [2]. Classification of Solid dispersions [2] Solid dispersions have been classified as follows depending on the type of carrier used for their preparation (Figure.1) Fig 1: The Classification of Solid Dispersions Solubility Enhancement Strategies in Solid Dispersions Melting and solvent evaporation methods have been the two major processes of preparing solid dispersions melting on lab scale [3]. Industrially relevant and applicable methods for solid dispersion manufacturing are explained in Figure (2) Fig 2: Manufacturing processes used to produce solid dispersions The objective of the study is to prepare Ritonavir solid dispersion by direct compression technology using different polymers to achieve the enhanced solubility and to determine the Kinetic Modeling of Drug Release. Available online: October Issue 268

4 MATERIALS AND METHOD Ritonavir Supplied by Pharma Train., Hyderabad. Polymers like PEG6000, Crosspovidone, Sorbitol, Mannitol, Microcrystalline cellulose, Aerosil, Magnesium Stearate supplied by Pharma Train Research Lab, Hyderabad. Characterization of the formulation Pre formulation study Preformulation stability studies are usually the first quantitative assessment of chemical stability of a drug as well as stability in presence of other excipients. The primary objectives of this investigation are identification of stable storage conditions for drug in the solid state and identification of compatible excipients for a formulation. Preformulation studies were performed on the drug, which include melting point determination, solubility and compatibility studies. Melting point: Melting point of Ritonavir was determined by capillary method. Solubility: Solubility of Ritonavir was determined in water, methanol, methylene chloride, ethyl ether and buffers. Preparation of standard curve of ritonavir Reagents: Methanol, 0.1N Hcl Standard solution of ritonavir 100mg of drug is dissolved in 100ml of methanol. This is first stock solution.10ml of 1 st stock solution is diluted with 100ml of buffer. This is 2 nd stock solution. Now from 2 nd stock, various concentrations of 10ug/ml, 15ug/ml, 30ug/ml, and 45ug/ml were prepared by using buffer. Blank was also prepared with same buffer composition except the drug. UV scanning was done for pure drug nm in methanol. The lambda max was found at 239nm. Compatibility studies Compatibility with excipients was confirmed by FTIR studies. The pure drug and its formulation along with excipients were subjected to FTIR studies. In the present study, the potassium bromide disc (pellet) method was employed. Available online: October Issue 269

5 Fourier Transform Infrared Spectroscopy (FTIR) Interpretation: The infrared spectra of pure Ritonavir samples were recorded by SHIMADZU FTIR spectrometer, equipped with an Inferometer detector. Samples were prepared by KBr disc method (2 mg sample in 100 mg KBr) and examined in the transmission mode. Each spectrum was measured over a frequency range of cm 1.The software used for the data analysis was Perkin-Elmer Spectrum The peaks obtained in the spectra were then compared with corresponding functional groups in the structures of Ritonavir. Formulation Development Table 1: Composition of solid dispersion tablets Ingredients F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 (mg) (mg) (mg) (mg) (mg) (mg) (mg) (mg) (mg) (mg) Ritonavir PEG Copovidone 50 Sorbitol Mannitol 100 Extragranular exicipents MCC Cross povidone Aerosil Magnesium stearate Total Preparation of Tablets: Method 1 Sorbitol was melted in crucible china dish at º.For batches with PEG add it along with sorbitol and heat around 50-70º as the T g of sorbitol is lowered because of PEG. Sift all the Available online: October Issue 270

6 extra granular excipients through mesh no 40 and add these to granules obtained in step 2 and blend. Compress using suitable punch. Method 2 Dissolve the drug in ethanol and transfer this solution to carry to make slurry. And with batches containing copovidone/peg add these to drug solution. Dry the slurry at 50-60º to evaporate ethanol completely. Pass the dried granules through mesh no 40. Sift all the extra granular excipients through mesh no 40 and add these to granules obtained in step 2 and blend. Compress using suitable punch. Pre compression studies Pre compression studies like Bulk density, Tap density, Angle of repose, Compressibility index, Hausner s ratio was carried out for the formulation. Post compression studies Post compression studies like Hardness, Friability, Content uniformity, Weight variation, In vitro drug release studies and Release Kinetics was carried out for the prepared formulations. In-vitro release studies [4-8] In-Vitro drug release studies were carried out using Tablet dissolution test apparatus USPXXIII at 50 rpm. The dissolution medium consisted of 900 ml Standard buffer 0.1N HCL. The temperature was maintained at 37 0 C 1 º C.The sample of 5ml was withdrawn at predetermined time intervals and an equivalent amount of fresh dissolution fluid equilibrated at the same temperature was replaced. The samples withdrawn were filtered through Whattman filter paper (No.1) and drug content in each sample was analyzed by UV-visible spectrophotometer at 239nm. Release kinetics [9-11] The results of in vitro release profile obtained for all the formulations were plotted in modes of data treatment as follows. Cumulative percent drug release versus time (zero order kinetic model) Log cumulative percent drug remaining versus time (first order kinetic model) Available online: October Issue 271

7 RESULTS AND DISCUSSION In the present study 10 formulations were prepared and evaluated for pre formulation characteristics compatibility studies, pre compression characteristics, post compression characteristics, invitro release studies and release kinetics. Pre formulation studies Melting point Melting point of Ritonavir was found to be in the range of c which complied with the standard, indicating purity of the drug sample. Solubility It is freely soluble in methanol and ethanol, soluble in isopropanol and practically insoluble in water. Compatibility Study Compatibility studies were performed using FT-IR spectrophotometer. The FT-IR spectrum of pure drug (fig 3) and physical mixture of drug and polymers (fig 8) were studied. The interpretation results were summarized in table no (2) Table 2: FTIR Interpretation S No Wave number(cm -1 ) Type of stretch N-H C=O C-H &2 0 Amines Available online: October Issue 272

8 Fig 3: FTIR spectra of Ritonavir Fig 4: FTIR Spectra of Ritonavir and all excipients Fig 5: FTIR spectra of Ritonavir and PEG6000 Fig 6: FTIR Spectra of Ritonavir and crospovidone Fig 7: FTIR spectra of Ritonavir and Sorbitol Fig 8: FTIR Spectra of Ritonavir and Mannitol Available online: October Issue 273

9 Fig 9: FTIR spectra of Ritonavir and MCC Fig10: FTIR of Ritonavir & Croscaramellose sodium Standard curve of Ritonavir Standard curve of Ritonavir was determined by plotting absorbance V/s concentration at 239 nm and it follows the Beer s law. The results were shown in table no (3). The r 2 value was found to be Table 3: Standard curve of Ritonavir S.No Concentration (µg/ml) Absorbance at 239nm Figure 11: Standard curve of Ritonavir Available online: October Issue 274

10 Pre compression studies Table 4: Pre compression parameters Formulation code Bulk Density (g/cc) Tapped density (g/cc) Angle of repose (degree) Carr s index (%) Hausner ratio F F F F F F F F F F Post compression studies: Table 5: Post compression parameters S.No. Formulation Weight variation Hardness (kg/cm2) Diameter (mm) Thickness (mm) Friability (%) 1 F1 complies Available online: October Issue 275

11 2 F2 complies F3 complies F4 complies F5 complies F6 complies F7 complies F8 complies F9 complies F10 complies In-Vitro Drug Release Studies According to USP, dissolution test for ritonavir tablets was done by using 0.1N HCL for 1hr at 50rpm using USP type 2 dissolution apparatus. Table 6: In-Vitro Drug Release of formulations Time(hrs) F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 Marketed formulation Available online: October Issue 276

12 Fig 12: Dissolution profile of F1-F3 Fig 13: Dissolution profile of F4-F6 Fig 14: Dissolution profile of F7-F9 Fig 15: Dissolution profile of F10 Release kinetics Fig 16: Dissolution profile of optimized & marketed formulation R 2 value s for optimized formulations were summarized in the table no (7). Table 7: R 2 values for optimized formulation Formulation Zero order First order Optimized formulation Available online: October Issue 277

13 Fig 17: Zero order plot Fig 18: First order plot All the prepared formulations were tested for physical parameters like weight variation, thickness, hardness and friability found to be within the pharmacopoeias limits. The average percentage deviation of 20 tablets of each formulation was maintained constant; the weight variation of the tablets were within the permissible limits of 5%.Weight of the tablet was fixed at 300mg and the weight variation for every batch was tested and found within the acceptance limits. The hardness of all batches ranged from 3-4 kg/cm 2. (Table no. 5).Percentage friability was below 1%. Friability test of all the formulations was found satisfactory showing enough resistance to the mechanical shock and abrasion. (Table no 5).Drug content uniformity in all formulations was calculated and the percent of active ingredient ranged from The in vitro dissolution study of F1, F2 and F3 were performed for 1hr time period. The results indicated that F1 and F2 and F3 formulations were unable to control the release of drug over 1hr time period. The results of dissolution studies of formulations F1, F2 and F3 were shown in figure (12). The dissolution study for F4, F5 and F6 were performed for 1hr time period. The F4 formulation containing PEG6000 and sorbitol releases 92% of drug in 45 minutes time period. F5 formulation consisting of PEG6000 and mannitol controls the drug release for 1hr and 95% of drug is released in 45 minutes time period. F6 formulation containing sorbitol was unable to control the drug release over 1 hr time period. The drug release at 45 minutes was 78%. The results of dissolution studies of formulations F4, F5 and F6 were shown in figure (13). The dissolution study for F7 F8 and F9 were performed for 1hr time period. F7 formulation containing sorbitol was unable to control the drug release over 1hr time period. The drug release at 45 minutes was 87%.F8 formulation containing sorbitol higher in Available online: October Issue 278

14 concentration than in F7 formulation release 91% of drug in 45 minutes time period. F9 formulation consisting of copovidone and sorbitol was able to control the drug release and releases 94% of the drug in 45 minutes time period. The results of dissolution studies of formulations F7, F8 and F9 were shown in figure (14), F10 formulation consisting of PEG6000 and sorbitol was able to control the drug release and it releases 96% of drug at 45 th minute. So it is considered as the optimized formulation as it shows better drug release than other formulations. The results of dissolution studies formulation F10 were shown in the figure (15). The dissolution profiles of optimized and marketed formulations were compared. From the results it was confirmed that the optimized formulation (F10) showed better drug release i.e. 96% than marketed formulation which showed 86% drug release at the end of 45 th minute. The results were shown in figure (16). Kinetic modeling of drug release The mechanism of release for the optimized formulation was determined by finding the R 2 value for each kinetic model viz. Zero-order and First-order. Thus from the results it can be said that the drug release follows Zero order kinetics. CONCLUSION The present work on enhancement of solubility of ritonavir tablets by solid dispersion technique utilize PEG 6000, copovidone, sorbitol and mannitol to increase the solubility of the formulation in 1hr time period. F10 formulation showed better drug release of 96% drug release at the end of 45 th minute compared to other formulations and marketed formulation. So F10 is the optimized formulation. Among the polymers used the role of PEG6000, copovidone and sorbitol is noteworthy in enhancing the solubility. Drug-excipients interaction was carried out for pure drug and optimized formulations by using FTIR study. In this analysis drug excipients compatibility interactions were not observed. From the results obtained it was concluded that the optimized formulation follows zero order release kinetics. REFERENCES 1. Leuner C, Dressman J., Improving drug solubility for oral delivery using solid dispersions. Eur. J. Pharm. Biopharm.,50: Available online: October Issue 279

15 2. Vasanthavada M, Tong W, Serajuddin ATM.,2008. Development of Solid Dispersion for Poorly Water-Soluble Drugs, in: R. Liu (Ed.), Water-Insoluble Drug Formulation, second edition., CRC Press, Taylor and Francis Group, Boca Raton, FL: Vasconcelos T, Sarmento B, Costa P., Solid dispersions as strategy to improve oral bioavailability of poor water soluble drugs, Drug Discov. Today.,12: Gong Y, Grant DJW, Brittain HG., Principles of Solubility, in: P. Augustijns, M. E. Brewster (Eds.), Solvent Systems and Their Selection in Pharmaceutics and Biopharmaceutics, Springer Science + Business Media, LLC, New York.,pp USP 28-NF 23, 2005The United States Pharmacopoeial Convention, Rockville, MD:pp Zamora I, Ridderstrom M, Ungell A, Andersson T, Afzelius L. Progress in ADME Prediction Using GRID-Molecular Interaction Fields, in: G. Cruciani (Ed.), Molecular Interaction Fields -, Wiley-VCH, Verlag, GmbH & Co. KGaA, Weinheim, Applications in Drug Discovery and ADME Prediction.:pp Mannhold R, Berellini G, Carosati E, Benedetti P. Use of MIF-based VolSurf Descriptors in Physicochemical and Pharmacokinetic Studies, in: G. Cruciani (Ed.), Molecular Interaction Fields - Applications in Drug Discovery and ADME Prediction, Wiley-VCH, Verlag, GmbH & Co. KGaA, Weinheim, 2006.: pp H. G. Brittain, Ionic Equilibria and the ph Dependence of Solubility, in: P. Augustijns, M. E. Brewster (Eds.).,2007. Solvent Systems and Their Selection in Pharmaceutics and Biopharmaceutics, Springer Science + Business Media, LLC, New York.:pp Yu L., An Integrated Model for Determining Causes for Poor Oral Drug Absorption. Pharm. Res.,16: Prentis RA, Lis Y, Walker SR., Pharmaceutical Innovation by Seven UK owned Pharmaceutical Companies. Br. J. Clin. Pharmacol.,25: J. P. F. Bai, J. Guo, Chaubal MV., Use of Nonactive Pharmaceutical Excipients in Oral Drug Formulations: Biopharmaceutical Classification System Considerations, in: A. Katdare, M. V. Chaubal (Eds.), Excipient Development for Pharmaceutical, Biotechnology, and Drug Delivery Systems, Informa Healthcare, USA: Available online: October Issue 280