Research Article K. Ravi Shankar et al. /BioMedRx 2013,1(3), Available online through www.jpronline.info Factorial Studies on Enhancement of Solubility and Dissolution Rate and Formulation Development of Efavirenz Tablets Employing ß Cyclodextrin and Soluplus *Corresponding author. Prof. K.P.R. Chowdary Former Principal, A. U. College of Pharmaceutical Sciences, Andhra University, Visakhapatnam 530003, Andhra Pradesh, India K. Ravi Shankar 1 and K. P. R. Chowdary* 2 1 A.KR.G College of Pharmacy, Nallajerla - 534112, Andhra Pradesh, India * 2 Former Principal, A. U. College of Pharmaceutical Sciences, Andhra University, Visakhapatnam - 530003, Andhra Pradesh, India Received on:17-01-2012; Revised on: 19-02-2013; Accepted on:27-02-2013 ABSTRACT Efavirenz, a widely prescribed anti retroviral drug belongs to class II under BCS and exhibit low and variable oral bioavailability due to its poor aqueous solubility. Its oral absorption is dissolution rate limited and it requires enhancement in the solubility and dissolution rate for increasing its oral bioavailability. The objective of the study is to enhance the solubility and dissolution rate of efavirenz by cyclodextrin complexation along with Soluplus and to evaluate the individual main effects and combined (or interaction) effects of ß cyclodextrin (ßCD) and surfactant (Soluplus) on the solubility and dissolution rate of efavirenz in a series of 2 2 factorial experiments. The solubility of efavirenz in four selected fluids containing ßCD and Soluplus as per 2 2 factorial study was determined. Solid inclusion complexes of efavirenz-ßcd were prepared with and without Soluplus by kneading method as per 2 2 -factorial design and were evaluated. The feasibility of formulating the drug- ßCD- Soluplus complexes into compressed tablets was also evaluated in a 2 2 factorial study. The individual and combined effects of ßCD and Soluplus in enhancing the solubility, dissolution rate and dissolution efficiency of efavirenz were highly significant (P < 0.01).ßCD alone gave a 2.14 fold increase in the solubility of efavirenz. Combination of ßCD with Soluplus resulted in a much higher enhancement in the solubility of efavirenz, 86.96 fold than with ßCD alone. Soluplus alone gave a much higher enhancement (289.49 folds) in the solubility of efavirenz. Combination of ßCD with Soluplus also gave significantly higher dissolution rates (K 1 ) when compared to ßCD alone. ßCD alone gave 2.00 fold increase and in combination with Soluplus, it gave 7.34 fold increase in the dissolution rate of efavirenz. Efavirenz ßCD, Efavirenz Soluplus and efavirenz ßCD Soluplus inclusion complexes could be formulated into compressed tablets by direct compression method. Efavirenz dissolution was rapid and higher from the tablets formulated employing drug- ßCD- Soluplus inclusion complexes when compared to the tablets containing efavirenz alone. The tablets formulated employing drug- ßCD- Soluplus inclusion complexes fulfilled the official (I.P 2010) dissolution rate test specification of NLT 70 % in 30 min prescribed for efavirenz tablets. The individual as well as combined effects of the two factors involved i.e., ßCD (factor A) and Soluplus (factor B) were highly significant (P< 0.01) in enhancing the dissolution ) and dissolution efficiency (DE 30 ) of efavirenz. Soluplus alone also gave a higher enhancement in the dissolution rate and dissolution efficiency of efavirenz and efavirenz tablets. Hence a combination of ßCD with Soluplus and / or Soluplus alone is recommended to enhance the solubility, dissolution rate and dissolution efficiency of efavirenz, a BCS class II drug and its tablet formulations. Key words: Efavirenz, ß Cyclodextrin, Soluplus, Solubility, Dissolution Rate, Efavirenz Tablets, Formulation development. INTRODUCTION Efavirenz, a widely prescribed HIV- 1 specific non nucleoside reverse transcriptase inhibitor drug belongs to class II under BCS and exhibit low and variable oral bioavailability due to its poor aqueous solubility. It is practically insoluble in water and aqueous fluids. As such its oral absorption is dissolution rate limited and it requires enhancement in solubility and dissolution rate for increasing its oral bioavailability. Several techniques 1 such as micronization, cyclodextrin complexation, use of surfactants and solubilizers, solid dispersion in water soluble and dispersible carriers, use of salts, prodrugs and polymorphs which exhibit high solubility, micro emulsions and self emulsifying micro and nano disperse systems have been used to enhance the solubility, dissolution rate and bioavailability of poorly soluble drugs. Among the various approaches complexation with cyclodextrins has gained good acceptance in recent years in industry for enhancing the solubility and dissolution rate of poorly soluble drugs. Cyclodextrins (CDs) are cyclic torus-shaped molecules with a hydrophilic outer surface and a lipophilic central cavity which can accom-
K. Ravi Shankar et al. /BioMedRx 2013,1(3), modate a variety of lipophilic drugs. As a consequence of inclusion process many physico-chemical properties such as solubility, dissolution rate, stability and bioavailability can be favourably affected 2, 3. Cyclodextrins have been receiving increasing application in pharmaceutical formulation in recent years due to their approval by various regulatory agencies 4, 5. Soluplus is a polymeric solubiliser with an amphiphilic chemical nature, which was particularly developed for solid solutions 6. Soluplus is polyvinyl caprolactam polyvinyl acetate polyethylene glycol graft co- polymer. Soluplus increased the solubility and enhanced the bioavailability of actives in solid solutions. Itraconazole and fenofibrate showed significant increase in the bioavailability with Soluplus 6. The solubility and dissolution rate of valsartan was effectively enhanced by using Soluplus in the form of solid dispersions 7. Poly vinyl pyrrolidone (PVP K 30) is also reported 8, 9 to enhance the solubility and dissolution rate of poorly soluble drugs. Though cyclodextrin complexation and use of surfactants and PVP for enhancing the solubility and dissolution rate of poorly soluble drugs have been investigated individually, no reports are available on their combined use in enhancing the solubility and dissolution rate. In the present investigation the individual main effects and combined (or interaction) effects of ß cyclodextrin (ßCD) and surfactant (Soluplus) on the solubility and dissolution rate of efavirenz, a BCS class II drug were evaluated in a 2 2 factorial study. The feasibility of formulating the drug- ßCD- Soluplus complexes into compressed tablets was also evaluated in a 2 2 factorial study. EXPERIMENTAL Materials Efavirenz was a gift sample from M/s. Eisai Pharmatechnology and Manufacturing Pvt. Ltd., Visakhapatnam. ß Cyclodextrin was gift sample from M/s. Cerestar Inc., USA. Soluplus was a gift sample from BASF, the chemical company, Hyderabad. Methanol (Qualigens), Avicel PH 102 and poly vinyl pyrrolidone (PVP K30) were procured from commercial sources. All other materials used were of pharmacopoeial grade. Methods Estimation of Efavirenz A UV Spectrophotometric method based on the measurement of absorbance at 245 nm in water containing 2 % Sodium lauryl sulphate (SLS) was used for the estimation of efavirenz. The method was validated for linearity, accuracy, precision and interference. The method obeyed Beer s law in the concentration range of 0-10 µg/ml. When a standard drug solution was repeatedly assayed (n=6), the relative error and coefficient of variance were found to be 0.85% and 1.20 % respectively. No interference by the excipients used in the study was observed. temperature (28±1 o C) on Rotary Flask Shaker. After 24 h of shaking, 2 ml aliquots were withdrawn at 2 h interval and filtered immediately using a 0.45 µ disk filter. The filtered samples were diluted suitably and assayed for efavirenz by measuring absorbance at 245 nm. Shaking was continued until two consecutive estimations are the same. The solubility experiments were replicated for three times each (n=3). Preparation of Efavirenz - ßCD Complexes Solid inclusion complexes of efavirenz ßCD - Soluplus were prepared as per 2 2 factorial study by kneading method. Efavirenz, ßCD and Soluplus were triturated in a mortar with a small volume of solvent consisting of a blend of dichloromethane: methanol (1:1). The thick slurry formed was kneaded for 45 min and then dried at 55 o C until dry. The dried mass was powdered and sieved to mesh No. 120. Preparation of Efavirenz- ßCD Soluplus tablets Compressed tablets each containing 50 mg of efavirenz were prepared as per 2 2 factorial study by direct compression method employing efavirenz- ßCD - Soluplus inclusion complexes as per the formulae given in Table 3. All ingredients as per the formula were blended in a closed polyethylene bag and were compressed into tablets on a 16- station tablet punching machine (M/s Cadmach machineries Pvt. Ltd., Ahmedabad) to a hardness of 5-6 kg/cm 2 using 9 mm flat punches. In each case 100 tablets were compressed. Evaluation of tablets: Hardness of the tablets was tested using a Monsanto hardness tester. Friability of the tablets was determined in a Roche friabilator. Disintegration time of the tablets prepared was determined using a Thermonic tablet disintegration test machine using water as test fluid. Dissolution rate study: The dissolution rate of efavirenz from the ßCD - Soluplus inclusion complexes and tablets prepared was studied in 900 ml water containing 1 % Sodium lauryl sulphate (SLS) using Disso 2000 (Labindia) 8- station dissolution test apparatus with a paddle stirrer at 50 rpm. A temperature 37±1 o C was maintained throughout the study. Inclusion complex equivalent to 50 mg of efavirenz or one tablet containing 50 mg of efavirenz was used in each test. Samples of dissolution media (5 ml) were withdrawn through a filter (0.45 µ) at different intervals of time, suitable diluted and assayed for efavirenz at 245 nm. The sample of dissolution fluid withdrawn at each time was replaced with fresh fluid. The dissolution experiments were replicated three times each (n=3). Analysis of results: Dissolution data were subjected to analysis as per zero order and first order kinetics and the corresponding dissolution rates were calculated. Dissolution efficiency (DE 30 ) values were calculated as suggested by Khan 10. Solubility and dissolution data were also analyzed by Analysis of Variance (ANOVA) as per 2 2 factorial study. Solubility Determination Excess drug (50 mg) was added to 15 ml of each fluid taken in a 25 ml stoppered conical flask and the mixtures were shaken for 24 h at room RESULTS AND DISCUSSION The objective of the study is to enhance the solubility and dissolution rate of efavirenz by cyclodextrin complexation along with Soluplus
K. Ravi Shankar et al. /BioMedRx 2013,1(3), and to evaluate the individual main effects and combined (or interaction) effects of ß cyclodextrin (ßCD), and surfactant (Soluplus) on the solubility and dissolution rate of efavirenz in a series of 2 2 factorial experiments. The feasibility of formulating the drug- ßCD- Soluplus complexes into compressed tablets was also evaluated in a 2 2 factorial study. The individual main effects and combined (interaction) effects of ßCD (Factor A), and Soluplus (Factor B) on the aqueous solubility of efavirenz were evaluated in a series of 2 2 -factorial experiments. For this purpose, two levels of ßCD (0, 5 mm), and two levels of Soluplus (0, 1%) were selected in each case and the corresponding four treatments involved in the 2 2 - factorial study were purified water (1); water containing 5 mm ßCD (a); water containing 1% Soluplus (b); and water containing 5 mm ßCD and 1% Soluplus (ab). The solubility of efavirenz in the above mentioned fluids was determined (n=3) and the results are given in Table-1. The solubility data were subjected to Analysis of variance (ANOVA) to find out the significance of main and combined effects of ßCD and Soluplus on the solubility of efavirenz. The results of ANOVA indicated that the individual and combined effects of ßCD and Soluplus in enhancing the solubility of efavirenz were highly significant (P < 0.01). ßCD alone gave a 2.14 fold increase in the solubility of efavirenz. Combination of ßCD with Soluplus resulted in a much higher enhancement in the solubility of efavirenz (86.96 fold) than with ßCD alone. Soluplus alone gave a much higher enhancement (289.49 folds) in the solubility of efavirenz. Table1: Solubility of Efavirenz in Various Fluids as per 2 2 -Factorial Study Table 2: Dissolution Parameters of Efavirenz- ßCD-Soluplus Inclusion Complexes Prepared as per 2 2 Factorial Study. EF- ß Composition PD 10 Dissolution Increase Dissolution Increase CD (%) Rate (min -1 ) in K 1 Efficiency in DE 20 Complex (K 1 x 10 2 ) (no of (DE 20 ) (%) (no of ( x) (sd)) folds) (x) (sd) folds) E EF 47.21 6.39 (0.56) - 41.79 - (1.7) EF EF- ßCD (1:2) 66.68 12.83 2.00 62.38 1.49 a (4.5) (10.37) EF EF-Soluplus (1%) 98.40 46.96 7.34 85.74 2.05 b (1.35) (1.16) EF EF- ßCD (1:2) 92.64 28.46 4.41 82.12 1.96 ab Soluplus (1%) (0.55) (1.85) Fluid (code as per 2 3 - Solubility Increase in solubility factorial experiment) (mg/ml) (number of folds) Distilled water(1) 0.019 Water containing 5mM ßCD (a) 0.042 2.14 Water containing 1% Soluplus (b) 5.71 289.49 Water containing 5mM ßCD 1.71 86.96 And 1% Soluplus (ab) Fig.1: Dissolution Profiles of Efavirenz ßCD Inclusion Complexes Prepared by Employing ßCD and Soluplus as per 2 2 Factorial Design To evaluate the individual and combined effects of ßCD and Soluplus on the dissolution rate of efavirenz, solid inclusion complexes of efavirenz- ßCD were prepared with and without Soluplus as per 2 2 - factorial design. For this purpose two levels of ßCD (0 and 1:2 ratio of drug : ßCD) and two levels of Soluplus (0 and 1%) were selected and the corresponding four treatments involved in the 2 2 -factorial study were efavirenz pure drug (1); efavirenz- ßCD (1:2) inclusion binary complex (a); efavirenz - Soluplus (1%) binary complex (b); and efavirenz- ßCD (1:2) - Soluplus (1%) ternary complex (ab). The CD complexes were prepared by kneading method. All the solid inclusion complexes of efavirenz- ßCD - Soluplus prepared were found to be fine and free flowing powders. Low coefficient of variation (c.v.) values (< 1.2 %) in the percent drug content indicated uniformity of drug content in each batch of solid inclusion complexes prepared. The dissolution rate of efavirenz alone and from ßCD complexes was studied in water containing 1 % SLS as prescribed in IP 2010. The dissolu- tion of efavirenz followed first order kinetics with r (correlation coefficient) above 0.9150. Dissolution efficiency (DE 20 ) values were calculated as suggested by Khan 10. The dissolution parameters are given in Table-2. The dissolution of efavirenz was rapid and higher in the case of efavirenz- ßCD and efavirenz- ßCD - Soluplus complex systems prepared when compared to efavirenz pure drug as such. The dissolution profiles of various inclusion complexes prepared are given in Fig-1. The dissolution ) values were subjected to ANOVA to find out the significance of the main and combined effects of ßCD and Soluplus on the dissolution rate of efavirenz. ANOVA indicated that the individual main effects of ßCD and Soluplus and their combined effects in enhancing the dissolution )and dissolution efficiency (DE 20 ) were highly significant (P < 0.01). ßCD alone gave a 2.00 fold increase in the dissolution rate of (K 1 ) of efavirenz. When ßCD is combined with Soluplus the dissolution ) was significantly enhanced (4.41 fold). Soluplus ( )
K. Ravi Shankar et al. /BioMedRx 2013,1(3), alone also gave higher dissolution rates, 7.34 fold increase in the dissolution ) of efavirenz. DE 20 values were also much higher in the case of ßCD Soluplus solid complexes when compared to efavirenz pure drug. The feasibility of formulating efavirenz- ßCD - Soluplus solid inclusion complexes into tablets was evaluated by preparing efavirenz tablets employing the solid inclusion complexes by direct compression method. To evaluate the individual and combined effects of ßCD and Soluplus on the dissolution rate and efficiency of efavirenz tablets, tablets each containing 50 mg of efavirenz were formulated employing solid inclusion complexes of drug- ßCD - Soluplus as per 2 2 factorial design. For this purpose two levels of ßCD (0 and 1: 2 ratio of Drug : ßCD) and two levels of each of Soluplus ( 0 and 1%) were selected and the corresponding four treatments involved in the formulation of tablets as per 2 2 -factorial study were efavirenz pure drug (1); EF- ßCD (1:2) inclusion binary complex (a); EF - Soluplus (1%) binary mixture (b) and EF - ßCD (1:2) Soluplus (1%) ternary complex (ab). Table 3: Formulae of Efavirenz Tablets Prepared by Direct Compression Method Employing Drug- ßCD Soluplus Inclusion complexes Table 5.All the tablets prepared were found to contain efavirenz within 100 ± 2% of the labeled claim. Hardness of the tablets was in the range 5.0-6.5 Kg/cm 2. Percentage weight loss in the friability test was less than 0.5 % in all the cases. All the tablets formulated employing efavirenz - ßCD - Soluplus inclusion complexes disintegrated rapidly within 2 min. The dissolution rate of efavirenz from the tablets prepared was studied in 900 ml of water containing 1 % SLS as prescribed in I.P 2010. Dissolution of efavirenz from all the tablets prepared followed first order kinetics with the correlation coefficient (r) values above 0.919. Ingredient (mg / tablet) Efavirenz Tablet Formulation Efavirenz (1)** 50 - - - EF- ßCD (1:2) (a) - 150 - - EF Soluplus (1%) (b) - - 52.3 - EF - ßCD (1:2) Soluplus (1%) (ab) - - - 152.3 PVP K30 2.3 - - - Crasscarnellose sodium 9.2 9.2 9.2 9.2 Talc 2.3 2.3 2.3 2.3 Magnesium Stearate 2.3 2.3 2.3 2.3 Aerosil 1.15 1.15 1.15 1.15 Avicel PH 102 162.75 65.05 162.75 62.75 Total weight (mg) 230 230 230 230 EF: Efavirenz; ßCD: ß cyclodextrin; ** Figures in parentheses are codes as per 2 2 Factorial Design All the prepared tablets were evaluated for drug content, hardness, friability and disintegration time and dissolution rate of efavirenz. The physical properties of the tablets prepared are given in Table 4. The dissolution profiles of various tablets formulated are shown in Fig. 2.The dissolution parameters of the tablets prepared are summarized in Table 4: Physical Properties of Efavirenz Tablets Prepared Employing Drug- ßCD Soluplus by Direct Compression Method as per 2 2 Factorial Study Formulation Hardness Friability DT Drug code as per (Kg/sq. cm) (% weight (min- Content 2 2 factorial loss) sec) (mg/tablet) design 5.0 0.55 1-20 50.2 5.5 0.40 1-50 49.6 5.0 0.45 1-30 49.8 6.0 0.65 1-45 50.2 Fig.2: Dissolution Profiles of Efavirenz ßCD tablets Prepared by Employing ßCD and Soluplus as per 2 2 Factorial Design Table 5: Dissolution Parameters of Efavirenz Tablets Prepared as per 2 2 Factorial Study Employing Drug-ßCD-Soluplus Inclusion Complexes EF- ß Composition PD 10 Dissolution Increase Dissolution Increase CD (%) Rate (min -1 ) in K 1 Efficiency in DE 20 Complex (K 1 x 10 2 ) (no of (DE 20 ) (%) (no of ( x) (sd)) folds) (x) (sd) folds) EF 24.82 1.46 (0.015) - 27.88(1.24) - EF- ßCD (1:2) 58.54 13.32 (0.04) 9.21 66.49(4.67) 2.38 EF-Soluplus (1%) 45.51 9.97(0.02) 6.89 49.95(11.2) 1.79 EF- ßCD (1:2) 62.31 9.41(0.015) 6.53 65.16 (4.15) 2.33 Soluplus (1%) Efavirenz dissolution was rapid and higher from the tablets formulated employing drug- ßCD- Soluplus inclusion complexes when compared to the tablets containing efavirenz alone. Dissolution parameters, K 1 and DE 30 were subjected to ANOVA to find out the significance of the individual and combined effects of the two factors (ßCD, Soluplus) in enhancing the dissolution rate and efficiency of efavirenz tablets. The individual as well as combined effects of the two factors
K. Ravi Shankar et al. /BioMedRx 2013,1(3), involved i.e., ßCD (factor A) and Soluplus ( factor B ) were highly significant (P< 0.01) in enhancing the dissolution ) and dissolution efficiency (DE 30 ) of efavirenz. Formulation formulated with ßCD alone gave higher enhancement in the dissolution rate (9.21 fold) when compared to control formulation formulated with efavirenz alone. Formulations containing Soluplus i.e. and gave relatively low dissolution when compared to formulation. The low dissolution observed with tablet formulations containing Soluplus is due to its binding nature reported earlier 6. I.P 2010 prescribed a dissolution rate specification of NLT 70% in 30 min for efavirenz tablets. All the efavirenz tablets formulated employing with drug- ßCD ( ), drug Soluplus ( ) and drug- ßCD Soluplus ( ) inclusion complexes fulfilled the official (I.P) dissolution rate specification of efavirenz tablets. Whereas plain tablets formulated employing efavirenz alone did not fulfill the official dissolution rate specification. Hence Soluplus alone or a combination of ßCD with Soluplus is recommended to enhance the dissolution rate and dissolution efficiency of efavirenz tablets. CONCLUSIONS 1. The individual and combined effects of ßCD and Soluplus in enhancing the solubility, dissolution rate and dissolution efficiency of efavirenz were highly significant (P < 0.01). 2. ßCD alone gave a 2.14 fold increase in the solubility of efavirenz. Combination of ßCD with Soluplus resulted in a much higher enhancement in the solubility of efavirenz, 86.96 fold than with ßCD alone. 3. Soluplus alone gave a much higher enhancement (289.49 folds) in the solubility of efavirenz. 4. Combination of ßCD with Soluplus also gave significantly higher dissolution rates (K 1 ) when compared to ßCD alone. ßCD alone gave 2.00 fold increase and in combination with Soluplus, it gave 7.34 fold increase in the dissolution rate of efavirenz. 5. Efavirenz ßCD, Efavirenz Soluplus and efavirenz ßCD Soluplus inclusion complexes could be formulated into compressed tablets by direct compression method. 6. Efavirenz dissolution was rapid and higher from the tablets formulated employing drug- ßCD- Soluplus inclusion complexes when compared to the tablets containing efavirenz alone. Source of support: Nil, Conflict of interest: None Declared 7. The tablets formulated employing drug- ßCD- Soluplus inclusion complexes fulfilled the official (I.P 2010) dissolution rate test specification of NLT 70 % in 30 min prescribed for efavirenz tablets. 8. The individual as well as combined effects of the two factors involved i.e., ßCD ( factor A) and Soluplus ( factor B) were highly significant (P< 0.01) in enhancing the dissolution ) and dissolution efficiency (DE 30 ) of efavirenz. 9. Soluplus alone also gave a higher enhancement in the dissolution rate and dissolution efficiency of efavirenz and efavirenz tablets. 10. Hence a combination of ßCD with Soluplus and / or Soluplus alone is recommended to enhance the solubility, dissolution rate and dissolution efficiency of efavirenz, a BCS class II drug and its tablet formulations. REFERENCES 1. Chowdary, K. P. R and Madhavi, BLR, Novel Drug Delivery Technologies for Insoluble Drugs, Indian Drugs, 2005 42 (9), 557 562. 2. Fromming, K.H. and Szejtli, J. Cyclodextrins in Pharmacy. Kluwer Academic Publications, Dordrecghi, 1994, p 20. 3. Duchene, D., Woussidjewe, D. and Dumitriu, S. Polysaccharides in Medical Applications. Marcel Dekker, New York, 1996, 575-602. 4. Thompson, D.O. Crit Rev Therapeutic Drug Carrier System. 1997, 14 (1), 1-104. 5. Hedges, A.R. Chemical Review. 1998, 98, 2035-2044. 6. Hendrik Hardung, Dejan Djuric, Shaukat Ali, Drug Delivery Technology, 2010,10 (3), XX. 7. Raja Rajeswari.K, Abbulu. K and Sudhakhar.M, J. Chem. Pharm. Res., 2011, 3(1): 180-187. 8. Giri, T. K., Badwaik, H., Alexander, A., and Tripathi, D. K., Int. J. Applied Biology and Pharmaceutical Tech., 2010, 1 (2), 793-800. 9. Aejaz, A., Jafar, M. Dehghan, M. H. G., and Adil Shareef, S.,. Int. J. Pharm. and Pharmaceutical Sci., 2010, 2 (1), 182-190. 10. Khan, K.A., Journal of Pharmacy and Pharmacology. 1975, 27, 48-49.