Formulation and Evaluation of Self microemulsifying drug delivery system of low solubility drug for enhanced solubility and dissolution

Atorvastatin is a BCS class II lipid lowering agent. It is insoluble in aqueous solution of pH 4 and below; it is very slightly soluble in water and pH 7.4 phosphate buffer. In the present investigation an attempt has been made to enhance solubility and dissolution of poorly soluble drug by formulating self microemulsifying drug delivery system (SMEDDS). The solubility of atorvastatin in individual microemulsion components viz. oil and surfactants was determined. The surfactants were screened for emulsification ability. Based on the solubility determinations and emulsification properties sunflower oil and surfactants cremophor RH 40 and capmul MCM C8 were selected for further study. The solubility o f atorvastatin in different ratios of selected oil and surfactants was determined. The composition of oil:surfactants with maximum solubility for atorvastatin was used for SMEDDS formulation. Pseudoternary phase diagrams were used to evaluate the microemulsification existence area. Formulation development and screening was done based on results obtained from phase diagrams and characteristics of resultant microemulsions. The microemulsions were evaluated for emulsion droplet size, self emulsification and phase separation, In vitro dissolution and stability. The SMEDDS formulation showed complete release in 30 min. as compared with the plain drug, which showed a limited dissolution rate.