Abstract:

Evidence on the role of phosphatidylcholine (PC) as a membrane permeability enhancer was the driving force in forming new liq. nanosized (modified microemulsions) oral delivery system contg. PC mols. We have demonstrated the feasibility of constructing phase diagrams with a large isotropic regions capable of being fully dild. with water. The microemulsions were stabilized with mixts. composed of PC and nonionic surfactant (polyoxyethylene-40 hydrogenated castor oil, HECO40) and short-chain org. acid as cosurfactant/cosolvent. When propionic acid served as the cosurfactant/cosolvent, the isotropic region was at its max. (ca. 72% of the total phase diagram area). The presence of a blend of PC and HECO40 seems to have synergistic effects, forming an isotropic region comprising 72% of the area of the phase diagram, in comparison to 20 and 50% in systems stabilized by PC and HECO40, alone, resp. The role of the PC mols. in the formation of those microemulsions is demonstrated by comparing three soy lecithins. Lecithin with a high PC content forms larger isotropic regions with more "free diln." lines. Several nonionic surfactants were investigated, yet only HECO40 seems to have a packing parameter suitable for the formation of large isotropic U-type systems. [on SciFinder(R)]