Abstract
In this paper we present a mathematical diffusion model describing the transient transdermal penetration of two non-volatile substances, the lipophilic flufenamic acid and the hydrophilic caffeine, after finite dosing in an aqueous vehicle system. A striking feature of this microscopic diffusion model is its ability to predict concentration-depth profiles. Relevant input parameters are obtained from a previously published infinite dose study (Naegel et al in Eur J Pharm Biopharm 68:368–379,
2008
; Hansen et al in Eur J Pharm Biopharm 68:352–367,
2008
). The quality of the model has been evaluated by comparing the concentration-depth profiles in stratum corneum (SC) and deeper skin layers of the experiment with those of the simulation. The results from the experiment and the simulation are in good agreement. The study addresses benefits and shortcomings of the model, and discusses future perspectives such as incorporating different morphological regions of the SC.