Guinea pig ear as a new model for in vivo percutaneous absorption.

A new animal model for in vivo percutaneous absorption utilizing the hairless, relatively thick skin of the guinea pig ear is proposed. Topical absorption studies were carried out with [14C]hydrocortisone and [14C]testosterone. Systemic studies were also conducted to correct for incomplete urinary excretion. In addition, a single stratum corneum correction factor was developed from published data to enable the guinea pig ear skin to be directly compared with human forearm skin. A comparison of human percutaneous absorption with the corrected guinea pig ear absorption shows a high correlation for both hydrocortisone and testosterone. The effects of ambient changes in relative humidity are also discussed with respect to in vivo percutaneous absorption.