CHAPTER VI FACTORIAL STUDIES ON THE EFFECTS OF CYCLODEXTRINS AND SOLUTOL HS15 ON THE SOLUBILITY AND DISSOLUTION RATE OF EFAVIRENZ AND RITONAVIR

Transcription

1 CHAPTER VI FACTORIAL STUDIES ON THE EFFECTS OF CYCLODEXTRINS AND SOLUTOL HS15 ON THE SOLUBILITY AND DISSOLUTION RATE OF EFAVIRENZ AND RITONAVIR Efavirenz and ritonavir, two widely prescribed anti retroviral drugs, are poorly soluble in water and aqueous fluids, exhibit low and variable oral bioavailability. They require enhancement in solubility and dissolution rate for increasing their oral bioavailability. In the present study two cyclodextrins (βcd and HPβCD) and a surfactant (Solutol HS15) were tried to enhance the solubility and dissolution rate of efavirenz and ritonavir. The individual main effects and combined (interaction) effects of cyclodextrins and the surfactant on the solubility and dissolution rate of efavirenz and ritonavir were evaluated in a series of 2 2 factorial experiments. β-cd and HP- β-cd were used in the study as they are non toxic and relatively less costly when compared to α-cd and γ-cd. α-cd and γ-cd are highly water soluble than β-cd and HP- β-cd and as such they are hygroscopic and likely to create problems in solid dosage form formulation and preparation. Hence α-cd and γ-cd are not included in the study. EXPERIMENTAL MATERIALS 1. Efavirenz and Ritonavir were gift samples from M/s Amoli Organics Pvt., Ltd., Mumbai, 2. β-cyclodextrin and hydroxy propyl β-cyclodextrin were gift samples from Signet Chemical Corporation Pvt., Ltd., Mumbai

2 3. Solutol HS15 was a gift sample from Dr. Reddy s Laboratories Ltd, Hyderabad. 4. Polyvinyl pyrrolidone ( PVP K-30 ). 5. Cross carmellose sodium, gift sample from M/s Natco Pharma Ltd., Hyderabad. 6. Talc, I.P. 7. Magnesium stearate, I.P. 8. Lactose, I.P. All other materials used were of pharmacopoeial grade. Methods: Determination of solubility: The solubility of ( i ) efavirenz and ( ii ) ritonavir in the following four selected fluids as per 2 2 factorial study was determined to evaluate the individual and combined effects of the cyclodextrins and the surfactant on the solubility of efavirenz and ritonavir. The two levels of CD (factor a) are 0 and 5 mm. The two levels of surfactant (factor b) are 0 and 2%. The selected f luids as per 2 2 factorial study are as follows: I. For Efavirenz- βcd-solutol HS15 system Statistical code as per Description 2 2 Factorial Design ( 1 ) Purified water ( a ) Water containing βcd (5 mm) ( b ) Water containing Solutol HS15 ( 2 % ) Water containing βcd (5 mm) and Solutol HS15 ( ab ) ( 2 % )

3 II. For Efavirenz- HPβCD-Solutol HS15 system Statistical code as per 2 2 Factorial Design Description ( 1 ) Purified water ( a ) Water containing HPβCD (5 mm) ( b ) Water containing Solutol HS15 ( 2 % ) ( ab ) Water containing HPβCD (5 mm) and Solutol HS15 ( 2 % ) III. For Ritonavir-βCD-Solutol HS15 system Statistical code as per 2 2 Factorial Design Description ( 1 ) Purified water ( a ) Water containing βcd (5 mm) ( b ) Water containing Solutol HS15 ( 2 % ) ( ab ) Water containing βcd (5mM) and Solutol HS15 ( 2 % ) IV. For Ritonavir-HPβCD-Solutol HS15 system Statistical code as per 2 2 Factorial Design Description ( 1 ) Purified water ( a ) Water containing HPβCD (5 mm) ( b ) Water containing Solutol HS15 ( 2 % ) ( ab ) Water containing HPβCD (5 mm) and Solutol HS15 ( 2 % )

4 Procedure: Excess drug was added to 15 ml of the selected fluid taken in a 25ml stoppered conical flask and the mixtures were shaken for 72 hours at room temperature (28 0 C) on a rotary flask shaker. After 72 hrs of shaking to achieve equilibrium, 2 ml of aliquots were withdrawn and filtered immediately using 0.45µ disc filter. The filtered samples were diluted suitably and assayed at 246 nm in the case of efavirenz and at 210 nm in the case of ritonavir. In each case the solubility determinations were replicate 4 times (n=4). Preparation of Drug -CD- Surfactant systems: To evaluate the individual and combined effects of cyclodextrins and surfactant on the dissolution rate of (i) efavirenz and (ii) ritonavir, drug -CDsurfactant systems were prepared employing the following selected combinations of CD and surfactant in each case as per a 2 2 factorial design. The two levels of CD (factor a) are 1: 0 and 1:2 ratio of drug: CD respectively. The two levels of surfactant (factor b) are 0 and 2%. The following are the selected treatments as per 2 2 factorial design in each case to evaluate the individual and combined effects. The selected treatments (products) as per 2 2 factorial study in each case are as follows. I. For Efavirenz- βcd-solutol HS15 system Statistical code as per Description 2 2 Factorial Design ( 1 ) Efavirenz pure drug ( a ) Efavirenz-βCD (1:2) binary system ( b ) Efavirenz-Solutol HS15 ( 2 % ) binary system ( ab ) Efavirenz-βCD-Solutol HS15 (1:2:0.02) ternary system

5 II. For Efavirenz- HPβCD-Solutol HS15 system Statistical code as per 2 2 Factorial Design Description ( 1 ) Efavirenz pure drug ( a ) Efavirenz-HPβCD (1:2) binary system ( b ) Efavirenz-Solutol HS15 ( 2 % ) binary system ( ab ) Efavirenz-HPβCD-Solutol HS15 (1:2:0.02) ternary system III. For Ritonavir-βCD-Solutol HS15 system Statistical code as per 2 2 Factorial Design Description ( 1 ) Ritonavir pure drug ( a ) Ritonavir-βCD (1:2) binary system ( b ) Ritonavir-Solutol HS15 ( 2 % ) binary system ( ab ) Ritonavir-βCD-Solutol HS15 (1:2:0.02) ternary system IV. For Ritonavir-HPβCD-Solutol HS15 system Statistical code as per 2 2 Factorial Design Description ( 1 ) Ritonavir pure drug ( a ) Ritonavir-HPβCD (1:2) binary system ( b ) Ritonavir-Solutol HS15 ( 2 % ) binary system ( ab ) Ritonavir-HPβCD-Solutol HS15 (1:2:0.02) ternary system The above mentioned binary and ternary systems were prepared by kneading method employing βcd, HPβCD and Solutol HS15. Preparation method: Required quantities of drug, βcd and surfactant were taken in a clean and dry mortar. Kneading fluid consisting of water: alcohol (1:1) was added and mixed to get a thick slurry. The slurry was thoroughly mixed and kneaded for 45 min. Additional quantities of kneading fluid was added to maintain the mixture as thick slurry during

6 the kneading process. After kneading for 45 min the mixture was transferred to a petridish and dried in an oven at 60 0 C. The dried powder was passed through mesh No.100. Estimation of drug content in drug-cd-surfactant complexes prepared: Drug-CD-surfactant complex powder equivalent to 50 mg of the medicament was taken into a boiling test tube and extracted with 4 x 10 ml quantities of methanol. The methanolic extracts were collected into 50 ml volumetric flask and the volume was made upto 50 ml with methanol. The solution was subsequently diluted with water containing 2%SLS in the case of efavirenz and with 0.1N hydrochloric acid in the case of ritonavir and assayed for the drug content by the UV spectrophotometric methods described in Chapter V. From each product four samples were analysed for drug content. Dissolution Rate study on Drug-CD-Surfactant Systems: The dissolution rate of medicament from the drug-cd-surfactant systems prepared was studied in water containing 2%SLS ( 900 ml ) in the case of efavirenz and in 0.1N hydrochloric acid ( 900 ml ) in the case of ritonavir using Disso 2000 (Labindia) 8-station dissolution test apparatus with a paddle stirrer at 50 rpm. A temperature of 37 C ± 1 C was maintained throughout the study. Complex system equivalent to 50 mg of drug was used in each test. Samples of dissolution media (5 ml) were withdrawn through a filter (0.45µ) at different intervals of time, suitably diluted and assayed for efavirenz at 246 nm and for ritonavir at 210 nm. The sample of dissolution fluid withdrawn at each time was replaced with fresh fluid. The dissolution experiments were replicated four times each ( n=4 )

7 RESULTS: Table -6.1 Solubility of Efavirenz in Various Fluids (N=4) as Per 2 2 Factorial Study (Efavirenz -βcd-solutol HS15) Fluid Solubility(mg/100 ml) x ± sd Increase in solubility (no. of folds) Purified water 1.20 ± Water containing βcd(5mm) 5.23 ± Water containing Solutol HS15 (2%) ± Water containing βcd (5mM) and Solutol HS15 (2%) ± Table -6.2 ANOVA of Solubility Data of Efavirenz -βcd-solutol HS15 Source of F-Ratio Significance d.f. S.S M.S.S Variation Total Treatments P< 0.01 a (β-cd) P<0.01 b (Solutol HS15) P<0.01 ab (combination) P<0.01 Error

8 Table -6.3 Solubility of Efavirenz in Various Fluids (N=4) as Per 2 2 Factorial Study (Efavirenz -HPβCD-Solutol HS15) Fluid Solubility(mg/100 ml) x ± sd Increase in solubility (no. of folds) Purified water 2.46 ± Water containing HPβCD(5mM) Water containing Solutol HS15 (2%) Water containing HPβCD (5mM) and Solutol HS15 (2%) 4.68 ± ± ± Table -6.4 ANOVA of Solubility Data of Efavirenz -HPβCD-Solutol HS15 Source of Variation d.f. S.S M.S.S F-Ratio Significance Total Treatments P< 0.01 a (HPβCD) P<0.01 b (Solutol HS15) P<0.01 ab (combination) P<0.01 Error

9 Table- 6.5 Solubility of Ritonavir in Various Fluids (N=4) as Per 2 2 Factorial Study (Ritonavir-βCD-Solutol HS15) Solubility (mg/100 ml) Increase in solubility Fluid x ± sd (no. of folds) Purified water 5.42 ± Water containing βcd (5mM) Water containing Solutol HS15 (2%) Water containing βcd (5mM) and Solutol HS15 (2%) 8.53 ± ± ± Table 6.6 ANOVA of Solubility Data of Ritonavir- βcd-solutol HS15 Source of F-Ratio Significance d.f. S.S M.S.S Variation Total Treatments P< 0.01 a (βcd) P<0.01 b (Solutol HS15) P<0.01 ab (combination) P<0.01 Error

10 Table- 6.7 Solubility of Ritonavir in Various Fluids (N=4) as Per 2 2 Factorial Study (Ritonavir-HPβCD-Solutol HS15) Solubility (mg/100 Increase in solubility Fluid ml) x ± sd (no. of folds) Purified water 5.42 ± Water containing HPβCD(5mM) Water containing Solutol HS15 (2%) Water containing HPβCD (5mM) and Solutol HS15 (2%) 6.32 ± ± ± Table 6.8 ANOVA of Solubility Data of Ritonavir-HPβCD-Solutol HS15 Source of Variation d.f. S.S M.S.S F-Ratio Significance Total Treatments P<0.01 a (HPβ-CD) P>0.01 b (Solutol HS15) P<0.01 ab (combination) P>0.01 Error

11 Table- 6.9 Percent Drug Content of Various CD-Surfactant Complex Systems Prepared CD complex system Drug content ( % ) x ( c.v ) Efavirenz -βcd (1:2) 32.8 (1.1 ) Efavirenz -HPβCD (1:2) 33.6 (1.2 ) Efavirenz -βcd-solutol HS15 (1:2 : 0.02) 33.8 (0.8 ) Efavirenz -HPβCD-Solutol HS15 (1:2 : 0.02) 34.2 (0.9 ) Ritonavir-βCD (1:2) 33.6 (1.2 ) Ritonavir-HPβCD (1:2) 33.8 (0.8 ) Ritonavir-βCD-Solutol HS15 (1:2 : 0.02) 34.6 (1.2 ) Ritonavir-HPβCD-Solutol HS15 (1:2 : 0.02) 34.6 (1.2 ) Table Dissolution Profiles of Efavirenz -βcd-solutol HS15 Systems Formulated as Per 2 2 Factorial Design Time Percent Efavirenz Dissolved ( x ± sd) (min) (1) (a) (b) (ab) ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±

12 Fig. 6.1 Dissolution Profiles of Efavirenz -βcd-solutol HS15 Systems Formulated as Per 2 2 Factorial Design log Percent Drug Remaining Time ( min ) 70 1 (a) (b) (ab) Fig. 6.2 First order Dissolution Profiles of Efavirenz -βcd-solutol HS15 Systems Formulated as Per 2 2 Factorial Design

13 Table Dissolution Profiles of Efavirenz -HPβCD-Solutol HS15 Systems Formulated as Per 2 2 Factorial Design Time Percent Efavirenz Dissolved ( x ± sd) (min) (1) (a) (b) (ab) ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± Percent Drug Dissolved Time ( min ) -1 ( a ) ( b ) ( ab ) Fig. 6.3 Dissolution Profiles of Efavirenz -HPβCD-Solutol HS15 Systems Formulated as Per 2 2 Factorial Design

14 log Percent Drug Remaining Time (min ) 1 (a) (b) (ab) Fig. 6.4: First order Dissolution Profiles of Efavirenz -HPβCD-Solutol HS15 Systems Formulated as Per 2 2 Factorial Design Table-6.12 ANOVA of K 1 x 10 2 (min -1 ) values of Efavirenz Complexes Formulated Employing βcd and Solutol HS15 as per 2 2 Factorial Design Source of Variation d.f. S.S M.S.S F-Ratio Significance Total Treatments P< 0.01 a (βcd) P< 0.01 b (SOLUTOL P< 0.01 HS15) ab (combination) P< 0.01 Error

15 Table ANOVA of K 1 x 10 2 (min -1 ) values of Efavirenz Complexes Formulated Employing HPβCD and Solutol HS15 as per 2 2 Factorial Design Source of Variation d.f. S.S M.S.S F-Ratio Significance Total Treatments P< 0.01 a (HPβCD) P< 0.01 b (SOLUTOL P< 0.01 HS15) ab (combination) P< 0.01 Error Table Dissolution Profiles of Ritonavir -βcd-solutol HS15 Systems Formulated as Per 2 2 Factorial Design Time Percent Ritonavir Dissolved ( x ± sd) (min) (1) (a) (b) (ab) ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±

16 120 Percent Drug Dissolved Time (min) 1 (a) (b) (ab) Fig. 6.5 Dissolution Profiles of Ritonavir -βcd-solutol HS15 Systems Formulated as Per 2 2 Factorial Design 2.5 log Percent of Drug Remaining Time ( min ) 1 (a) (b) (ab) Fig. 6.6 First order Dissolution Profiles of Ritonavir -βcd-solutol HS15 Systems Formulated as Per 2 2 Factorial Design

17 Table Dissolution Profiles of Ritonavir -HPβCD-Solutol HS15 Systems Formulated as Per 2 2 Factorial Design Time Percent Ritonavir Dissolved ( x ± sd) (min) (1) (a) (b) (ab) ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± Percent Drug Dissolved Time ( min ) 1 ( a ) ( b ) ( ab ) Fig. 6.7: Dissolution Profiles of Ritonavir -HPβCD-Solutol HS15 Systems Formulated as Per 2 2 Factorial Design

18 2.5 log Percent Drug Remaining Time ( min ) 1 (a) (b) (ab) Fig. 6.8 First order Dissolution Profiles of Ritonavir -HPβCD-Solutol HS15 Systems Formulated as Per 2 2 Factorial Design Table-6.16 ANOVA of K 1 x 10 2 (min -1 ) values of Ritonavir Complexes Formulated Employing βcd and Solutol HS15 as per 2 2 Factorial Design Source of Variation d.f. S.S M.S.S F-Ratio Significance Total Treatments P< 0.01 a (βcd) P< 0.01 b (SOLUTOL P< 0.01 HS15) ab (combination) P< 0.01 Error

19 Table-6.17 ANOVA of K 1 x 10 2 (min -1 ) values of Ritonavir Complexes Formulated Employing HPβCD and Solutol HS15 as per 2 2 Factorial Design Source of Variation d.f. S.S M.S.S F-Ratio Significance Total Treatments P< 0.01 a (HPβCD) P< 0.01 b (SOLUTOL P< 0.01 HS15) ab (combination) P< 0.01 Error

20 DISCUSION OF RESULTS: Efavirenz and ritonavir, two widely prescribed anti retroviral drugs, are poorly soluble in water and aqueous fluids and exhibit low and variable oral bioavailability. They requires enhancement in solubility and dissolution rate for increasing their oral bioavailability. In the present study two cyclodextrins (βcd and HPβCD) and a surfactant (Solutol HS15) were used to enhance the solubility and dissolution rate of both efavirenz and ritonavir. The individual main effects and combined (interaction) effects of cyclodextrins and the surfactant on the solubility and dissolution rate of efavirenz and ritonavir were evaluated in a series of 2 2 factorial experiments. Solubility Studies: 1. Effect of βcd and Solutol HS15 on the Solubility of Efavirenz : The results of solubility studies with βcd and Solutol HS15 are given in Table 6.1.The solubility of efavirenz was markedly enhanced by βcd and Solutol HS15. A 4.35 and fold increase in the solubility of efavirenz was observed respectively with βcd (5mM) and Solutol HS15 (2%) when used alone. A combination of βcd (5mM) and Solutol HS15 (2%) gave a fold increase in the solubility of efavirenz The solubility data were subjected to Analysis of Variance (ANOVA) to find out the significance of individual main and combined ( interaction ) effects of βcd and Solutol HS15 on the solubility of efavirenz The results of ANOVA are given in Table 6.2. ANOVA indicated that the individual main effects of βcd and Solutol HS15 as well as the combined effects are highly significant (P<0.01). A combination of βcd and Solutol HS15 has resulted in a much higher enhancement on the solubility of efavirenz than is possible with them individually. This may be due to better inclusion of drug molecules in the presence of Solutol HS

21 2. Effect of HPβCD and Solutol HS15 on the Solubility of Efavirenz: The results of solubility studies with HPβCD and Solutol HS15 are given in Table 6.3 The solubility of efavirenz was markedly enhanced by HPβCD and Solutol HS15. A 1.28 and fold increase in the solubility of efavirenz was observed respectively with HPβCD (5mM) and Solutol HS15 (2%). A combination of HPβCD (5mM) and Solutol HS15 (2%) gave a fold increase in the solubility of efavirenz,anova ( Table 6.4) indicated that the individual main effects of HPβCD and Solutol HS15 as well as the combined effects are highly significant (P<0.01). The increases in solubility of efavirenz (number of folds when compared to solubility in water) observed with CDs and surfactant alone and in combination are shown in Table Table Increase in Solubility of Efavirenz observed with CDs and Surfactant alone and in Combination CD / Surfactant Increase in solubility (no. of folds) βcd 4.35 HPβCD 1.53 Solutol HS βcd-solutol HS HPβCD- Solutol HS Among all CDs and surfactant, Solutol HS15 exhibited greater enhancement in the aqueous solubility (30.37 fold) of efavirenz The order of increasing enhancement observed with various CDs and Surfactant was Solutol HS15 > βcd >HPβCD. Among all the combinations, βcd-solutol HS15 exhibited greater enhancement in the aqueous solubility (54.43 fold) of efavirenz The order of

22 increasing enhancement observed with various combinations was βcd- Solutol HS15 > HPβCD- Solutol HS15. Thus combination of Solutol HS15 with CDs (βcd and HPβCD) resulted in a much higher enhancement in the solubility of efavirenz than is possible with CDs alone. Hence, a combination of CDs and Solutol HS15 is recommended for enhancing the solubility of efavirenz, a poorly soluble BCS Class II drug. 3. Effect of βcd and Solutol HS15 on the Solubility of Ritonavir: The results of solubility studies with βcd and Solutol HS15 are given in Table 6.5. The solubility of ritonavir was markedly enhanced by βcd and Solutol HS15. A 1.57 and fold increase in the solubility of ritonavir was observed respectively with βcd (5mM) and Solutol HS15 (2%) when used alone. A combination of βcd (5mM) and Solutol HS15 (2%) gave a fold increase in the solubility of ritonavir. The solubility data were subjected to Analysis of Variance (ANOVA) to find out the significance of individual main and combined (interaction) effects of βcd and Solutol HS15 on the solubility of ritonavir. The results of ANOVA are given in Table 6.6. ANOVA indicated that the individual main effects of βcd and Solutol HS15 as well as the combined effects are highly significant (P<0.01). A combination of βcd and Solutol HS15 has resulted in a much higher enhancement on the solubility of ritonavir than is possible with them individually. This may be due to better inclusion of drug molecules in the presence of Solutol HS Effect of HPβCD and Solutol HS15 on the Solubility of Ritonavir: The results of solubility studies with HPβCD and Solutol HS15 are given in Table 6.7. The solubility of ritonavir was significantly enhanced by HPβCD and Solutol HS15. A 1.47 and fold increase in the solubility of ritonavir was

23 observed respectively with HPβCD (5mM) and Solutol HS15 (2%). A combination of HPβCD (5mM) and Solutol HS15 (2%) gave a fold increase in the solubility of ritonavir. ANOVA (Table 6.8) indicated that the individual main effects of Solutol HS15 are highly significant (p<0.01) whereas individual main effects of HPβCD and combined effects of HPβCD (5mM) and Solutol HS15 (2%) are not significant (p>0.01) The increase in solubility of ritonavir (number of folds when compared to solubility in water) observed with CDs and surfactants alone and in combination are shown in Table Table Increase in Solubility of Ritonavir Observed with CDs and Surfactants alone and in Combination CD / Surfactant Increase in solubility (no. of folds) βcd 1.57 HPβCD 1.47 Solutol HS βcd-solutol HS HPβCD- Solutol HS Among all CDs and surfactant, Solutol HS15 exhibited greater enhancement in the aqueous solubility (21.72fold) of ritonavir. The order of increasing enhancement observed with various CDs and Surfactants was Solutol HS15 > βcd >HPβCD. Among all the combinations, βcd-solutol HS15 exhibited greater enhancement in the aqueous solubility (28.97fold) of ritonavir. The order of increasing enhancement observed with various combinations was βcd- Solutol HS15 > HPβCD- Solutol HS15. Thus combination of Solutol HS15 with CDs (βcd and HPβCD)

24 resulted in a much higher enhancement in the solubility of ritonavir than is possible with CDs alone. Hence, a combination of CDs and Solutol HS15 is recommended for enhancing the solubility of ritonavir, a poorly soluble BCS Class II drug. Effects of CDs and Surfactant on the Dissolution Rate of Efavirenz: To evaluate the individual main and combined effects of cyclodextrins (βcd and HPβCD) and surfactant, Solutol HS15 on the dissolution rate of efavirenz, solid inclusion complexes of Drug-CD-Surfactant were prepared in each case as per 2 2 factorial design. All the solid inclusion complexes prepared were found to be fine and free flowing powders. Low C.V values (< 1.5%) in the percent drug content indicated uniformity of drug content in each batch of solid inclusion complexes prepared (Table 6.9). The dissolution rate of efavirenz from various Drug-CD-Surfactant complexes prepared was studied in water containing 2% SLS. The dissolution profiles of the complexes prepared are given in Tables and shown in Figs Drug- CD and Drug-CD-Surfactant complexes gave rapid and higher dissolution of efavirenz when compared to efavirenz pure drug. The dissolution was much higher in the initial 5-10 min. The dissolution data were analyzed as per zero order and first order kinetics. Dissolution of efavirenz from all CD-Surfactant complexes prepared followed first order kinetics with correlation coefficient (r 2 ) values in the range The first order dissolution plots of various products are shown in Figs 6.2 and 6.4. The first order dissolution plots also exhibited two distinct phases, initial rapid dissolution phase up to 5 min. and later relatively slow dissolution phase in the case of CD-surfactant inclusion complexes. The dissolution rate constants were calculated in each case separately for 0-5 min. and 5-30 min. and the average of the two was calculated and reported as dissolution rate (K 1 ). The first order dissolution

25 rates (K 1 ) and Dissolution efficiency (DE 15 ) values, calculated as per Khan, are given in Table 6.20A. The dissolution rates (K 1 ) and Dissolution efficiency (DE 15 ) values were several times higher in the case of CD-Surfactant complexes when compared to efavirenz pure drug with all the systems prepared. The numbers of times that the DE 15 and K 1 values were enhanced or increased by the CDs and surfactant individually and in combination are shown in Table 6.20A. Table -6.20A Increase in DE 15 and K 1 values of Efavirenz by βcd and βcd Solutol HS15 DE 15 ( % ) K ( min -1 ) CD complex x Increase Increase x ( no. of folds ) ( no. of folds ) Efavirenz βcd Solutol HS βcd-solutol HS Table -6.20B Increase in DE 30 and K 1 values of Efavirenz by HPβCD and HP βcd Solutol HS15 DE 30 ( % ) K ( min -1 ) CD complex x Increase Increase x ( no. of folds ) ( no. of folds ) Efavirenz HPβCD Solutol HS HPβCD-Solutol HS

26 Among the individual effects, CDs (βcd and HPβCD) gave higher enhancement in the K 1 and DE 15 of efavirenz than the surfactant Solutol HS15 The order of increasing enhancement in K 1 and DE 15 observed with various CDs and surfactant was βcd > HPβCD > Solutol HS15. βcd gave highest increase in DE 15 (6.44 fold ) and K 1 ( 5.50 fold ) of efavirenz. The dissolution rate (K 1 ) values of various Drug-CD-Surfactant complex systems were subjected to Analysis of Variance (ANOVA) to evaluate the significance of the individual main and combined effects of CDs and surfactant in enhancing the dissolution rate ( K 1 ). The ANOVA of K 1 values are shown in Tables The results of ANOVA indicated that all individual and combined effects were highly significant (P < 0.01). Among other combined effects, βcd-solutol HS15 gave highest enhancement in K 1 (5.95). βcd alone gave an increase of 5.50 fold in the dissolution rate of efavirenz Combination of βcd with Solutol HS15 has further enhanced the dissolution rate ( K 1 ) of efavirenz by 5.95 folds. As β-cd have more OH groups at the surface to interact with the surfactant solutol, β-cd-solutol complexes gave higher enhancement in the solubility and dissolution rate than HP- β-cd-solutol systems. Effects of CDs and Surfactants on the Dissolution Rate of Ritonavir: To evaluate the individual main and combined effects of cyclodextrins (βcd and HPβCD) and surfactant Solutol HS15 on the dissolution rate of ritonavir, solid inclusion complexes of Drug-CD-Surfactant were prepared in each case as per 2 2 factorial design.all the solid inclusion complexes prepared were found to be fine and free flowing powders. Low C.V values ( < 1.5% ) in the percent drug content indicated uniformity of drug content in each batch of solid inclusion complexes prepared

27 The dissolution rate of ritonavir from various Drug-CD-Surfactant complexes prepared was studied in 0.1N hydrochloric acid The dissolution profiles of the complexes prepared are given in Tables ,15 and shown in Figs 6.5 and 6.7. Drug-CD and Drug-CD-Surfactant complexes gave rapid and higher dissolution of ritonavir when compared to ritonavir pure drug. The dissolution was much higher in the initial 5-10 min. The dissolution data were analyzed as per zero order and first order kinetics. Dissolution of ritonavir from all CD-Surfactant complexes prepared followed first order kinetics with correlation coefficient ( r 2 ) values in the range The first order dissolution plots of various products are shown in Figs 6.6 and 6.8. The first order dissolution plots also exhibited two distinct phases, initial rapid dissolution phase up to 5 min. and later relatively slow dissolution phase in the case of CD-surfactant inclusion complexes. The dissolution rate constants were calculated in each case separately for 0-5 min. and 5-30 min. and the average of the two was calculated and reported as dissolution rate ( K 1 ). The first order dissolution rates ( K 1 ) and Dissolution efficiency ( DE 15 ) values are given in Tables The dissolution rates ( K 1 ) and Dissolution efficiency ( DE 15 ) values were several times higher in the case of CD-Surfactant complexes when compared to ritonavir pure drug with all the systems prepared. The numbers of times that the DE15 and K1 values were enhanced or increased by the CDs and surfactants individually and in combination are shown in Table

28 Table Increase in DE 15 and K 1 values of Ritonavir by CDs and CD-Surfactant DE 15 ( % ) K ( min -1 ) Increase Increase x x CD complex ( no. of folds ) ( no. of folds ) Ritonavir βcd HPβCD Solutol HS βcd-solutol HS HPβCD-Solutol HS Among the individual effects, CDs (βcd and HPβCD) gave higher enhancement in the K 1 and DE 15 of ritonavir than the surfactant Solutol HS15. The order of increasing enhancement in dissolution rate ( K 1 ) observed with various CDs and surfactants was βcd > HPβCD > Solutol HS15. The order of increasing enhancement in dissolution efficiency (DE 15 ) observed with various CDs and surfactants was HPβCD > βcd > Solutol HS15. The dissolution rate ( K 1 ) values of various Drug-CD-Surfactant complex systems were subjected to Analysis of Variance ( ANOVA ) to evaluate the significance of the individual main and combined effects of CDs and surfactants in enhancing the dissolution rate ( K 1 ) of ritonavir. The ANOVA of K 1 values are shown in Tables The results of ANOVA indicated that all individual and combined effects were highly significant ( P < 0.01 ). Among the combined effects, βcd-solutol HS15 gave highest enhancement in K 1 (8.66 fold). ( K 1 ) of ritonavir

29 As β-cd have more OH groups at the surface to interact with the surfactant solutol, β-cd-solutol complexes gave higher enhancement in the solubility and dissolution rate than HP- β-cd-solutol systems. DRUG - EXCIPIENT COMPATIBILITY STUDY The compatibility of βcd and Solutol HS15 with efavirenz and ritonavir was evaluated by FT-IR and DSC study. FTIR Study: FTIR spectra of pure drugs and their βcd and βcd - Solutol HS15 complexes were recorded on a Jasco-450 Plus (Japan) IR spectrophotometer model: Spectrum RXI, using KBr disc as reference. The spectra are shown in Figures Differential Scanning Calorimetry (DSC): DSC thermograms of pure drugs and their βcd and βcd - Solutol HS15 complexes were recorded on a Perkin Elmer thermal analyzer. Samples (3-4mg) were sealed into aluminium pans and scanned at a heating rate of 10 C min -1 over a temperature range of C. The DSC thermograms are shown in Figures

30 Fig, 6.9 FTIR Spectra of ( A) Efavirenz and (B) Efavirenz-βCD (1:2) Complex Fig, 6.10 FTIR Spectra of ( A) Efavirenz and (B) Efavirenz-βCD Solutol HS15(1:2:0.05) Complex

31 Fig, 6.11 FTIR Spectra of ( A) Ritonavir and (B) Ritonavir-βCD (1:2) Complex Fig, 6.12 FTIR Spectra of ( A) Ritonavir and (B) Ritonavir-βCD Solutol HS15(1:2:0.05) Complex

32 Fig 6.13 DSC Thermogram of Efavirenz Fig 6.14 DSC Thermogram of Efavirenz-βCD (1:2) complex

33 Fig 6.15 DSC Thermogram of Efavirenz-βCD-Solutol HS15 (1:2:0.05) complex Fig 6.16 DSC Thermogram of Ritonavir

34 Fig 6.17 DSC Thermogram of Ritonavir-βCD (1:2) complex Fig 6.18 DSC Thermogram of Ritonavir-βCD-Solutol HS15 (1:2:0.05) complex

35 RESULTS AND DISCUSSION: The compatibility of βcd and Solutol HS15 with efavirenz and ritonavir was evaluated by FT-IR and DSC study. FTIR Study: The FTIR characteristic peaks efavirenz (Fig. 6.9) are NH stretching at 3318cm - 1,Aryl-CH stretching at 3095 and 3018cm -1,C C stretching at 2251cm -1,C=O stretching at1747cm -1,Ring C=C stretching at 1602, 1497, 1456cm -1,C-F stretching at 1186cm -1 and Out of plane =C-H band at 743cm -1. The spectra of both efavirenz pure drug and its βcd and βcd Solutol HS15 complexes (Figs ) also showed the above characteristic peaks. The FTIR spectra of ritonavir (Fig 6.11) indicated characteristic peaks at 3,480 cm 1 (N H stretching amide group), 2,964 cm 1 (hydrogen-bonded acid within the molecule), 1,716 cm 1 (ester linkage), 1,645, 1,622, and 1,522 cm 1 ( C C stretching aromatic carbons). The spectra of ritonavir pure drug and its βcd and βcd Solutol HS15 complexes (Figs ) also showed the above characteristic peaks. DSC Study: The DSC thermograms of pure drugs and their βcd and βcd Solutol HS15 complexes are shown in Figures All the thermograms exhibited sharp endothermic melting peaks

36 Table-6.22 The Melting Peaks Observed in DSC Thermograms are as Follows. S. No. Sample Melting point C 1 Efavirenz Efavirenz- βcd (1:2) complex Efavirenz- βcd-solutol HS15 (1:2:0.05) complex Ritonavir Ritonavir- βcd (1:2) complex Ritonavir- βcd-solutol HS15 (1:2:0.05) complex The melting points observed with both the drugs were in good agreement with the literature values in each case. The melting peaks were observed at the same temperature in each case for pure drug as well as its βcd (1:2) and βcd-solutol HS15 (1:2:0.05) complexes The FTIR and DSC studies, thus, indicated no interaction between βcd and Solutol HS15and the two drugs studied (efavirenz and ritonavir)