Estimation of the relative stratum corneum amount removed by tape stripping

Background/purpose: The tape stripping procedure is a suitable minimal invasive tool to study, e.g. the penetration and dermatopharmacokinetics of topically applied substances. In the present study, this procedure was used to remove the stratum corneum (SC) completely and to study the penetration of the UVA filter substance butyl methoxydibenzoylmethane after application in two different vehicles. Methods: The amount of corneocytes removed by each tape strip from the flexor forearm of human volunteers was determined via their pseudo-absorption. In a second part, the penetration profiles of a UVA filter substance applied in two different vehicles were determined following the developed standard protocol using the tape stripping procedure in combination with UV/VIS spectroscopy. Results: The amount of corneocytes removed by each tape strip was related to the number of tape strips used for removal. Mean values with a deviation of less than 20% concerning the relative amount of SC removed by a constant number of tape strips were obtained. For instance, a relative amount of 66 +/- 12% was removed with the first 20 tape strips, while nearly the complete SC (95 +/- 3%) was removed using 50 tape strips. In addition, these results were used to estimate the relative SC amounts removed, studying the penetration of the UVA filter substance after application in two different vehicles. No significant differences between the distributions of the UV filter substance applied in both emulsions were obtained (P > 0.05). Conclusions: The reported procedure for the estimation of the removed SC amount provides the possibility to avoid the complete removal of the SC and to compare the penetration characteristics obtained for different volunteers and different products in relation to the relative horny layer profile.