Critical factors determining the potency of topical corticosteroids.

The vasoconstrictor assay is a highly reliable method used to determine the bioequivalence of topical corticosteroid preparations. By assessing skin blanching, the assay describes the delivery of the active agent through the skin barrier, intrinsic activity at the receptor, and the rate of clearance from the site of application. Vasoconstrictor rankings are generally good predictors of efficacy in clinical trials. Vasoconstrictor assays are not as predictive of outcomes in clinical practice because these assays do not account for a critical factor: how well patients use the medication. Patient compliance plays a vital role in corticosteroid potency.