Bioavailability Enhancement of Ritonavir by Solid Dispersion Technique

Ritonavir is an antiretroviral agent used in the treatment of HIV-infection. It is a BCS class IV drug having poor aqueous solubility leading to poor bioavailability. Bioavailability is the amount of drug that enters the systemic circulation. The bioavailability is affected by various factors like solubility, dissolution and stability. In order to improve bioavailability, many techniques like solid dispersions, nanoparticles, liposomes, encapsulation methods were present. The main aim of this study is to improve the bioavailability of ritonavir with the help of Polyvinyl Pyrrolidone (PVP) K-30 by using solid dispersion technique. Different formulations were made with varied concentrations of polymer. Characterization of solid dispersion was done by phase solubility, drug content, Fourier transformed infrared spectroscopy (FT-IR), Differential Scanning Calorimetry (DSC) and in-vitro dissolution studies.  From phase solubility studies that apparent solubility constant was found to be 42.227M-1. The drug content of the binary system of ritonavir and PVP was found to be ranging from 99.17% to 103.06%. %. FT-IR studies revealed that there was no drastic change in the wave number indicating polymer compatibility with drug. In-vitro dissolution studies proved that there was an increase in drug release of ritonavir with incremental ratios of polymer and F5 formulation has shown almost 95% of drug release. Keywords: Bioavailability, Solid dispersion, Polyvinyl pyrrolidine, Solvent evaporation, Dissolution