Percutaneous absorption of corticosteroids: age, site, and skin-sectioning influences on rates of permeation of hairless mouse skin by hydrocortisone.

As part of a long-range plan to decipher the mechanism of mass transfer of corticosteroids across skin, the permeation of [3H]hydrocortisone through hairless mouse skin was characterized by in vitro diffusion cell techniques. Age and anatomical site-related behaviors were explored mainly with whole skin but also with skin stripped of its horny layer. Permeability of the mouse skin was low shortly after birth and increased during the singular normal hair cycle exhibited by the SKH-hr-1 mouse strain. The return to a hairless state over a period of 20-35 d was accompanied by decreased permeability of hydrocortisone. A permeability coefficient of approximately 2 X 10(-4) cm/h was found for the mature mouse. For whole skin, there was no difference in the permeabilities of dorsal and abdominal skin sections, but for stratum corneum-free membranes and dermal membranes, the abdominal site appeared to be more permeable, which is consistent with its thinner dimensions. Totally stripped skin and isolated dermis are approximately 500 and approximately 1000 times more permeable than intact skin, respectively; the unaltered stratum corneum of the hairless mouse is thus shown to be the major barrier to the mass transfer of hydrocortisone.