Skin penetration of nonsteroidal antiinflammatory drugs out of a lipophilic vehicle: influence of the viable epidermis.

The skin penetration of 10 nonsteroidal antiinflammatory drugs (NSAIDs) was investigated after application in the lipophilic vehicle light mineral oil. The skin permeabilities and maximum fluxes, which were calculated from the concentration decreases of the applied solutions in the steady state phases, were correlated with physicochemical parameters, mainly the vehicle solubilities and the partition coefficients of the model drugs according to the Fickian diffusion laws. The objective of the study was to characterize the barrier function of the stratum corneum and the viable epidermis and to predict their influences on the skin permeabilities and the maximum fluxes of the NSAIDs by model equations. The permeability of the human skin for NSAIDs applied in a lipophilic vehicle is a function of their hydrophilicity, while the maximum flux is primarily dependent on their vehicle solubilities. The viable epidermis was found to represent the decisive resistance to the drug transport.