Comparative enhancer effects of Span (R) 20 with Tween (R) 20 and Azone (R) on the in vitro percutaneous penetration of compounds with different lipophilicities

Sorbitan monolaurate (Span(R)20) was used in this study to analyze the infl uence of the polar functional group on the effects that non-ionic surfactan ts have on skill permeability. Its ethoxylate derivative polysorbate 20 (Tw een(R)20) and Azone(R), both with the same C12 alkyl chain as Span(R)20, we re used for comparative purposes. We evaluated the relative potency of the three molecules as enhancers in the permeability of a series of compounds w ith lipophilicities ranging from log Poct = - 0.95 to log Poct = 2.33. The influence of the enhancer concentration was also studied. For this purpose the epidermis of Wistar rat was pretreated with ethanolic solutions (1 and 5%, w/v) of each enhancer. Our results indicate that the nature of the enha ncer head group greatly influences cutaneous barrier impairment. The enhanc er concentration must also be taken into account, even though the influence of the concentration seems to depend on the lipophilicity of the penetrant assayed. (C) 2000 Published by Elsevier Science B.V. All rights reserved.