Skin Permeability In Vivo: Comparison in Rat, Rabbit, Pig and Man

A comparative study was undertaken in rats, rabbits, miniature swine and man, in which the percutaneous absorption of the following compounds, labeled with 14C or 35S, were studied: haloprogin, N-acetylcysteine, cortisone, testosterone, caffeine and butter yellow. The amount of radioactivity excreted in urine for 5 days following application of the test compound to the skin was employed as the index for quantifying skin penetration. A special nonocclusive foam pad device for rabbits and miniature swine was developed to prevent artifacts resulting from transfer of drug to the urine by any route other than percutaneous absorption. The dose was 4 μg/cm2 of skin surface. The excretion data obtained from the topical studies were adjusted for recovery of radioactivity following intravenous administration of the radioactive drug. The results obtained in this study indicated that skin permeability decreases in the following order: rabbit, rat, pig and man. Overall, skin of miniature swine has the closest permeability characteristics to that of human skin with this series of compounds