Role of transepidermal and transfollicular routes in percutaneous absorption of hydrocortisone and testosterone: in vivo study in the hairless rat.

The importance of the transappendageal route on percutaneous absorption was assessed in the hairless rat. Skin permeation of two steroids, hydrocortisone and testosterone, was evaluated in vivo on normal and artificially damaged skin in which follicles and sebaceous glands disappeared during healing. The test compounds were applied for periods of 0.5, 2 and 6 h. Thereafter, the stratum corneum reservoir function, the epidermal and dermal distribution profiles, and systemic absorption were determined for both molecules. The results presented here show that the reservoir function of the stratum corneum of appendage-free (scar) skin is more pronounced than that of normal skin, whereas the concentration appearing in the epidermis and dermis was greater in normal skin. Moreover, sebaceous glands probably contribute to the penetration of hydrocortisone and testosterone. We show that the relative importance of the skin appendages depends on the intrinsic physical properties of the molecules tested, and the time of application.