Correlation of the local distribution of topically applied substances inside the stratum corneum determined by tape-stripping to differences in bioavailability.

Tape-stripping and optical spectroscopy are used as a suitable combined method to determine the horny layer profile. Firstly, typical ultraviolet filter substances are used as active substances which are fixed inside the horny layer. Secondly, clobetasol propionate was applied topically in two formulations, Temovate Cream and Temovate and Emollient. The measured changes in the local distribution of the drug inside stratum corneum reflect the observed differences in the biological response visualized as blanching. The concentration of the drug in deeper parts of the horny layer proposes the existence of a small channel available for the percutaneous absorption. The observed low intensity blanching is correlated to the follicle orifices of the skin. After application of Temovate and Emollient, a lateral spreading of the drug must be taken into account. Copyright 2001 S. Karger AG, Basel