Formulation Design of Sel-Micro-Emulsifying Lipid Systems

Background: The increasing interest in the field of Lipid Self-Emulsifying Technology (LSET) is due to the fact that 40% of new chemical entities exhibit poor oral bioavailability because of their low water solubility. Self-Micro-Emulsifying Drug Delivery Systems (SMEDDS) are isotropic mixtures of oils, surfactants, and cosurfactants, which under gentle agitation in aqueous media form oil-in-water nano-emulsions of oil droplet size <100 nm. Materials and Methods: Self-emulsification process carried out at varying key compositions in the lipid mixtures; oil, cosurfactant and surfactant. Oil droplet size was measured using laser diffraction and light scattering techniques. Equilibrium phase behavior studies were carried out and phase boundaries were determined mapped out. Results: At least 40% w/w of cremophor EL is needed to obtain all the way through clear self-emulsifying clear dispersions (L2→L1) on the progressive addition of water. Maximum aqueous solubilization as L2 phase occurred at ≈ 55% w/w for miglyol 812 and {tagat TO/imwitor 988} blends at ratios of either (7:3). Conclusion: Successful self-micro-emulsifying lipid formulations were developed using droplet size measurements and equilibrium phase studies. Key elements in the oil blends were optimized which includes, type of oil, co-surfactant, surfactant and oil:co-surfactant ratio. Phase dynamic behavior due to the interaction of lipid vehicle with the aqueous media was investigated in an attempt to understand mechanistic of emulsification.