Penetration Enhancer Incorporation in Bilayers

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Abstract
A preliminary study has been made of the interaction and location of the penetration enhancing agent dodecyl-1-aza-cycloheptane-2-one (Azone) in a system which models certain elements of the lipid arrangements found in the stratum corneum. The model host comprises a nonionic surfactant which forms associated multimolecular structures through hydration interactions with the aqueous component of the system. Azone incorporation into the lamellar bilayer phase leads to a marked increase in ability of the phase to take up water. Small-angle X-ray diffraction and Deuterium NMR measurements indicate the degree of water and azone penetration into the bilayers to be inter-dependent. Similar behaviour is observed for oleyl alcohol but not by hydrotropic materials such as isopropyl alcohol or propylene glycol. The mechanism by which azone promotes the penetration of hydrophilic drugs is indicated to be related to its ability to increase the water capacity of the lipid matrix of the stratum corneum.