Preperation and in vitro evaluation of solid dispersions of nimodipine using PEG 4000 and PVP K30

Solid dispersions in water-soluble carriers have attracted considerable interest as a means of improving the dissolution rate, and hence possibly bioavailability, of a range of hydrophobic drugs. The aim of the present study was to improve the solubility and dissolution rate of a poorly water-soluble drug, nimodipine, by a solid dispersion technique. Solid dispersions were prepared by using polyethylene glycol 4000 (PEG- 4000) and polyvinylpyrrolidone K30 (PVPK30) in different drug-to-carrier ratios. The solid dispersions were prepared by melting method. Morphology of solid dispersions was characterised by scanning electron microscope. The pure drug, physical mixtures and solid dispersions were characterized by in vitro dissolution study. Dissolution characteristics were determined by using pH 4.5 acetate buffer containing 0.3% SDS. The very slow dissolution rate was observed for pure nimodipine and the dispersion of the drug in the polymers considerably enhanced the dissolution rate. This can be attributed to improved wettability and dispersibility, as well as decrease of the crystalline and increase of the amorphous fraction of the drug. Solid dispersions prepared with PEG-4000 and PVPK30 showed the highest improvement in wettability and dissolution rate of nimodipine. Even physical mixtures of nimodipine prepared with both polymers also showed better dissolution profile than that of pure nimodipine. In conclusion, dissolution of nimodipine can be enhanced by the use of hydrophilic carriers PEG-4000 and PVPK30.