Distribution of 3H-Betamethasone-17-Valerate After Topical Application in the Domestic Pig**From the Department of Pharmacology, University of Ottawa, Ottawa, Ontario, Canada.

The percutaneous absorption of sH-betamethasone-17-valerate was studied in young domestic pigs. Our findings suggest that this animal may serve as a suitable model for studying the absorption of steroids from the skin. A single application of radioactive cream was applied to the skin and kept there for three days under occlusion. Urine proved to be the main excretory route of this topical steroid. Excretion in feces was ten times less. After three days occlusion, an appreciable amount of radioactivity was recovered from all tissues; highest concentrations were present in the liver. Plasma samples revealed significant levels of radioactivity as early as two hours after application and reached their highest concentrations at the end of 72 hours. After a single application, maximal levels of radioactivity were also observed to persist in plasma for a period of nine days in the presence of constant occlusion. These findings are discussed with reference to the clinical use of topically applied steroids