Simvastatin has low aqueous solubility resulting in low oral bioavailability (5%) and thus presents a challenge in formulating a suitable dosage form. To improve the aqueous solubility, a solid dispersion formulation of Simvastatin was prepared by lyophilization utilizing skimmed milk as a carrier. Six different formulations were prepared with varying ratios of drug and carrier and the corresponding physical mixtures were also prepared. The improvement of amorphous state through solid dispersion was confirmed by differential scanning calorimetry and X-ray diffraction studies. The optimum drug-to-carrier ratio of 1:9 enhanced solubility nearly 30-fold as compared to pure drug. In-vitro drug release studies exhibited a cumulative release of 86.69% as compared to 25.19% for the pure drug. Additionally, scanning electron microscopy studies suggested the conversion of crystalline Simvastatin to an amorphous form. In a Triton-induced hyperlipidemia model, a 3-fold increase in the lipid lowering potential was obtained with the reformulated drug as compared to pure drug. These results suggest that solid dispersion of Simvastatin using skimmed milk as carrier is a promising approach for oral delivery of Simvastatin.
Keywords: Bioavailability; Simvastatin; dissolution; skimmed milk; solid dispersion; solubility; triton-induced hyperlipidemia.