Skin levels and vasoconstrictor assay of topically applied hydrocortisone.

Ointment containing 2.5% hydrocortisone was applied topically under occlusion to 84 subjects. Fifty-three percent of the population showed skin blanching in response to topical application of the steroid. To correlate vasoconstrictor response with drug level, hydrocortisone concentrations were determined fluorometrically in skin samples from 16 subjects in whom skin blanching was also assessed. The epidermal concentration of hydrocortisone was significantly greater in those subjects who exhibited blanching. Data suggest that a minimum epidermal reservoir of 200 micrograms of hydrocortisone per gram of lyophilized tissue is necessary to elicit a definite vasoconstrictor response.