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

Atorvastatin is a BCS class II lipid lowering agent. It is insoluble in aqueoussolution of pH 4 and below; it is very slightly soluble in water and pH 7.4phosphate buffer. In the present investigation an attempt has been made toenhance solubility and dissolution of poorly soluble drug by formulating selfmicroemulsifying drug delivery system (SMEDDS). The solubility ofatorvastatin in individual microemulsion components viz. oil and surfactantswas determined. The surfactants were screened for emulsification ability.Based on the solubility determinations and emulsification propertiessunflower oil and surfactants cremophor RH 40 and capmul MCM C8were selected for further study. The solubility of atorvastatin in differentratios of selected oil and surfactants was determined. The composition ofoil:surfactants with maximum solubility for atorvastatin was used for SMEDDSformulation. Pseudoternary phase diagrams were used to evaluate themicroemulsification existence area. Formulation development and screeningwas done based on results obtained from phase diagrams and characteristicsof resultant microemulsions. The microemulsions were evaluated foremulsion droplet size, self emulsification and phase separation, In vitrodissolution and stability. The SMEDDS formulation showed complete releasein 30 min. as compared with the plain drug, which showed a limiteddissolution rate.