Preparation and Evaluation of Self-microemulsifying Drug Delivery System of Sirolimus

The present investigation was aimed to enhance dissolution of sirolimus by liquid and solid selfmicroemulsifying drug delivery systems (SMEDDS). Solubility of sirolimus was determined in various vehicles, including oils, surfactants and co-surfactant. Emulsification study was conducted to identify the most suitable ratio of Oil:Smix (mixture of surfactant and co-surfactant). Various in vitro tests like emulsification time, cloud point, precipitation and thermodynamic stabilities were used to determine the composition of optimized formulation. SMEDDS with optimum composition were converted to solid using Florite RE. Adsorbed SMEDDS were further characterized by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), X-ray diffraction (XRD) and particle size analysis. DSC, XRD and SEM results of solid SMEDDS confirmed that the drug presented in the formulation was in an amorphous state. The optimized liquid and solid SMEDDS showed higher drug release than the powder sirolimus and found stable upto 2 months.