Occlusion effect on in vivo percutaneous penetration of chemicals in man and monkey: partition coefficient effects

Skin occlusion can increase the hydration of the stratum corneum up to 50%, which can have substantial effects on the percutaneous absorption of penetrants by altering skin barrier physiology. Though occlusion is widely utilized to enhance the penetration of applied drugs in clinical practice, it is not well known for which chemicals occlusion enhances the penetration through skin. In this review, we focus on what effect occlusion has on the percutaneous absorption of compounds of varying lipophilicities/hydrophilicities in vivo in the monkey and man.

Studies and prior reviews of the effects of occlusion on the in vivo percutaneous penetration of penetrants of varying liphophilicities/hydrophilicities were identified in the Medline, Pubmed, Embase and Science Citation Index databases.

After examining the research articles generated by the search results, 7 original research studies were obtained that used in vivo occlusion models and provided insight regarding the role of partition coefficients in predicting the effects of occlusion on percutaneous penetration. From these studies, one can conclude the following: (1) occlusion enhances the percutaneous absorption of many but not all compounds, (2) penetration can increase as the amount of time of occlusion increases, (3) occlusion seems to enhance the penetration of very lipophilic compounds more than that of very hydrophilic compounds, but (4) a relationship between a compound's octanol-water partition coefficient and its occlusion-induced enhancement has not been determined.

These in vivo studies reinforce the conclusions drawn from in vitro studies that partition coefficients incompletely predict the effect of occlusion on percutaneous penetration.