ENHANCEMENT OF SOLUBILITY AND DISSOLUTION RATE OF TELMISARTAN EMPLOYING β-CYCLODEXTRIN AND SOLUPLUS – A FACTORIAL STUDY

Telmisartan, a widely prescribed anti hypertensive drug belongs to class IΙ 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 Telmisartan by cyclodextrin complexation along with Soluplus and to evaluate the individual main effects and combined (or interaction) effects of β cyclodextrin (βCD) and surfactant (Soluplus) on the solubility and dissolution rate of Telmisartan in a series of 22 factorial experiments. The effects of βCD and Soluplus alone on the solubility of Telmisartan were evaluated by phase solubility studies. The solubility of Telmisartan in four selected fluids containing βCD and Soluplus as per 22 factorial study was determined. Solid inclusion complexes of Telmisartan-βCD were prepared with and without Soluplus by kneading method as per 22 - factorial design and were evaluated. The aqueous solubility of Telmisartan was increased linearly as a function of the concentration of βCD as well as Soluplus. The phase solubility diagram of Telmisartan - βCD complexes is of type AL. Increase in solubility of Telmisartan was due to the formation of a 1:1 M complex in solution with βCD with a stability constant (Kc) value of 326.0 M -1 . The individual and combined effects of βCD and Soluplus in enhancing the solubility and dissolution rate of Telmisartan were highly significant (P<0.01). βCD alone gave a 2.21 fold increase in the solubility of Telmisartan. Combination of βCD with Soluplus resulted in a much higher enhancement in the solubility of Telmisartan, 5.0 fold with βCD - Soluplus than with βCD alone. The dissolution of Telmisartan was rapid and higher in the case of Telmisartan - βCD complex systems when compared to Telmisartan pure drug. βCD alone gave a 1.96 fold increase in the dissolution rate (K1) of Telmisartan. When βCD is combined with Soluplus the dissolution rate (K1) was significantly enhanced to 4.37 fold with β CD - soluplus complexes. Hence complexation of Telmisartan with β CD - Soluplus is recommended to enhance the solubility and dissolution rate of Telmisartan, a BCS Class II drug. Key words: Telmisartan, β Cyclodextrin, Soluplus, Solubility, Dissolution rate, Factorial Study