Solubility enhancement of simvastatin: a review

Fairly soluble drugs in gastrointestinal (GI) media exhibit complete oral absorption, and thus good bioavailability. About 40% of drugs are not soluble in water in practice and therefore are slowly absorbed, which results in insufficient and uneven bioavailability and GI toxicity. Thus, most exigent phase of drug development practice particularly for oral dosage forms is the enhancement of drug solubility and thereby its oral bioavailability. Solubility, an important factor to achieve desired plasma level of drug for pharmacological response, is the phenomenon of dissolution of solid in liquid phase resulting in a homogenous system. This review describes various traditional and novel methodologies proposed for solubility enhancement of simvastatin, and ultimately improvement in its bioavailability. For simvastatin, solubility is a crucial rate limiting factor to achieve its desired level in systemic circulation for pharmacological response. Thus, problematic solubility of simvastatin is a main challenge for dosage form developing researchers. Various procedures, illustrated in this review, have been successfully employed to improve the simvastatin solubility for its bioavailability enhancement; however, successful improvement essentially depends on the assortment of technique. Among all the solubility enhancement techniques, solid dispersion method, in terms of ease and efficiency is most promising and routinely employed technique to resolve the solubility problems of simvastatin.