Determining dermal absorption parameters in vivo from tape strip data.

Tape stripping the outermost skin layer, the stratum corneum (sc), is a popular method for assessing the rate and extent of dermal absorption in vivo. Results from tape strip (TS) experiments can be affected significantly by chemical diffusion into the sc during the time required to apply and remove all of the TSs, tTS. Here, we examine the effects of this problem on the interpretation of TS experimental results. Dermal absorption of 4-cyanophenol (4CP) in humans was studied using TS experiments to assess conditions in which diffusion alters TS results. Mathematical models were developed to assess the effects of diffusion on parameter estimation. For an experiment with tTS > tlag (i.e., the lag time for a chemical to cross the sc), the permeability coefficient for 4CP, P(sc,v), calculated including tTS, was consistent with values from the literature (i.e., 0.0019 cm/h). When diffusion during stripping was not included in the model, P(sc,v) was 70% smaller. Calculations show that chemical concentrations in TSs can be affected by diffusion during tape stripping, but if tTS < 0.2 tlag and the exposure time is > 0.3 tlag, TS concentrations are not significantly affected by tTS.