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PREPARATION AND EVALUATION OF SOLID DISPERSIONS OF RITONAVIR IN STARCH 1500 AND SOLUPLUS ALONE AND IN COMBINATION

M.Priyadarsini, K. P. R. Chowdary* , S.V.U.M.Prasad

Ritonavir, a widely prescribed antiretroviral drug belongs to class II under BCS and exhibit low and variable oral bioavailability due to its poor aqueous solubility. As such it needs enhancement in the dissolution rate and bioavailability to derive its maximum therapeutic efficacy. The objective of the present study is to prepare and evaluate solid dispersions of Ritonavir in Starch 1500 and Soluplus alone and in combination for enhancing the dissolution rate and dissolution efficiency of Ritonavir. The individual and combined effects of the two carriers, Starch 1500 and Soluplus in enhancing the dissolution rate and dissolution efficiency of Ritonavir were evaluated in a 22 factorial study. Solid dispersions of Ritonavir in Starch 1500 alone were prepared using four ratios of drug: carrier namely 2:1, 1:1, 1:2 and 1:3 by solvent evaporation method. Solid dispersions of Ritonavir in Soluplus alone were prepared at three concentrations namely 0.5, 1.0 and 2% by common solvent method. Solid dispersions of Ritonavir in combined carriers namely Starch 1500 and Soluplus were prepared as per 22 factorial design. All the solid dispersions prepared were evaluated for drug content uniformity, dissolution rate and dissolution efficiency in comparison to Ritonavir pure drug. The dissolution rate and dissolution efficiency of Ritonavir could be significantly enhanced by solid dispersion in Starch 1500 and Soluplus alone and in combination. The individual and combined effects of Starch 1500 and Soluplus in enhancing the dissolution rate and dissolution efficiency of Ritonavir are highly significant (P < 0.01). Soluplus gave significant enhancement in the dissolution rate of Ritonavir at very low concentrations where as a large proportion of Starch 1500 is required for a similar enhancement in the dissolution rate of Ritonavir. Combination of Starch 1500 and Soluplus resulted in a much higher enhancement in the dissolution rate and dissolution efficiency of Ritonavir than is possible with them individually. A 7.56 and 3.12 fold increase in the dissolution rate of ritonavir was observed with starch1500 and soluplus respectively .whereas in combination they gave a 11.67 fold increase in the dissolution rate of ritonavir. Combination of Starch 1500 and Soluplus is recommended for enhancing the dissolution rate and dissolution efficiency of Ritonavir. Key words: Ritonavir, Solid dispersion, Dissolution Rate, Starch 1500, Soluplus, Factorial study.

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