Formulation and Evaluation of Self-Emulsifying Drug Delivery System of Orlistat

The objective of this study was to develop self-emulsifying drug delivery system (SEDDS) to enhance the solubility of the poorly water-soluble drug Orlistat. Orlistat is class II molecule according to BCS (Biopharmaceutical Classification System), having low solubility and low permeability. The rate and extent of absorption of class II compounds is highly dependent on the performance of the formulated product. These drugs can be successfully formulated for oral administration, but care needs to be taken with formulation design to ensure consistent bioavailability. Solubility of Orlistat was evaluated in various nonaqueous carriers that included oils, surfactants, and cosurfactants. Pseudoternary phase diagrams were constructed to identify the self-microemulsification region. Self microemulsifying formulations were prepared using mixtures of oils, surfactants, and cosurfactants in various proportions. The self microemulsification properties, droplet size and thermodynamic stability of these formulations were studied upon dilution with water. The optimized liquid SMEDDS formulation was converted into free flowing powder by adsorbing onto a solid carrier for encapsulation. The dissolution characteristics of solid intermediates of SMEDDS filled into hard gelatin capsules were investigated and compared with pure drug and commercial formulation. The results indicated that solid intermediates showed the rate and extent of drug dissolution for solid intermediates were significantly higher than commercial formulation. The results of the study demonstrated the potential use of SMEDDS as a means of improving solubility, dissolution and concomitantly the bioavailability.