ABSTRACT
Absorption of molecules (applied drugs and chemicals) through the skin proceeds
by sequential diffusion steps through the stratum corneum (SC, barrier), viable
epidermal, and dermal layers (1-3). Within each of these strata, absorption involves
partitioning into and diffusion within several components of an inherently
heterogeneous microstructure, and in the dermis it is accompanied by clearance
into the systemic circulation via the dermal vasculature. Microscopic theoretical
models of these transport processes have evolved to the point where they can
often yield mechanistic understanding and reasonable quantitative predictions
of transdermal transport rates, subsurface concentration levels, and rates of
vascular clearance.
