Diffusion and metabolism of prednisolone farnesylate in viable skin of the hairless mouse.

The diffusion and metabolism of prednisolone 21-farnesylate were investigated in viable skin of the hairless mouse in vitro. The prodrug ester was extensively metabolized in viable skin, while it was stable in the donor and receptor solutions. The rate of appearance of the prodrug and its metabolite prednisolone was markedly influenced by the direction of the skin placed between the in vitro diffusion half-cells. The rate of bioconversion of the prodrug was determined as a function of the distance from the surface of the skin. The prodrug was increasingly metabolized with the distance from the surface of the skin, indicating that the responsible enzymes are enriched in the lower layers of the viable skin. A model with linearly increasing enzyme activity in the viable skin accounts for the in vitro profiles of the diffusion/metabolism of the prodrug in the viable skin of hairless mouse.