Enhanced oral bioavailability of daidzein by self-microemulsifying drug delivery system

To enhance oral absorption of poorly water-soluble daidzein, self-microemulsifying drug delivery system (SMEDDS) composed of oil, surfactant and cosurfactant for oral administration of daidzein was formulated, and its physicochemical properties and pharmacokinetic parameters were evaluated. Solubility of daidzein was determined in various vehicles. Pseudo-ternary phase diagrams were constructed to identify the efficient self-microemulsification region and particle size distributions of the resultant microemulsions were determined using a laser diffraction sizer. From these studies, an optimized formulation consisting of Ethyl oleate (10%), Cremophor RH 40 (60%), and polyethylene glycol 400 (PEG400) (30%) was selected. The dissolution rate of daidzein from SMEDDS was significantly higher than the conventional tablet. Relative bioavailability of SMEDDS was enhanced about 2.5-fold compared with that of the control group. The data suggest that the use of SMEDDS provide a potential way of daidzein administered orally.