exact mathematical expressions give concentration-distance relationships of drug and metabolite as well as fluxes of the two molecules in terms of concentration of drug applied to the stratum corneum , permeability coefficient of drug in the stratum corneum , diffusion coefficients of drug and metabolite in the viable tissues ( epidermis and dermis ) , rate constants for the two enzyme systems , and the thickness of the viable tissue .
C0221921
stratum corneum
C0014520
epidermis