Early Stage Clinical

Paul Lehman, QPS Vice President and Head of Dermal and Transdermal Research, Publishes on Estimating Skin Permeation Parameters

Historically, percutaneous absorption permeation parameters have been derived from in vitro infinite dose studies, yet there is uncertainty in their accuracy if the applied vehicle saturates or damages the stratum corneum, or when the permeation parameters are inappropriately derived from cumulative absorption data. This article offers a simplified, tested approach for determining penetration parameters from in vitro finite dose data.

In the article, Lehman shows how key variables and equations for their derivation, as identified from the literature, can be used to calculate permeation parameters using only Tmax, AUC (area under drug concentration/time curve), and AUMC (area under first moment curve). From this finite dose absorption data, regardless of the length of the diffusion pathway through the membrane, three parameters can be obtained: the diffusion transit time (td), which characterizes the diffusion coefficient, the partition volume (VmP), which characterizes the partition coefficient, and the permeation coefficient (Kp).

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