The effect of the skin penetration enhancer Azone® on fatty acid-sodium soap-water mixtures

Abstract

The effect of Azone on the phase behaviour of a mixture of partly neutralised fatty acids in water was investigated by X-ray diffraction. The lipid blend consisted of saturated palmitic chains and unsaturated oleic chains. It was found that the system consisted of both crystalline and liquid crystalline phases at body temperature and below. The solid phases consisted essentially of the saturated lipids, while the unsaturated lipids formed the liquid crystalline phase. Azone had a minor effect on the crystalline phase, but partitioned into the liquid crystalline phase. The addition of Azone caused the original reversed hexagonal phase to be transformed into a reversed micellar phase. The findings presented here are in line with our previous observations on the effect of Azone on the soya bean lecithin-water and monoolein-water system, but in conflict with another study on a similar fatty acid system where it was assumed that Azone promoted the formation of the lamellar phase.