Abstract: Topical dermatologic drugs take effect at the target skin and the bioequivalence study methods for orally administrated drugs may not be applicable to topical dermatologic drug. Currently, vasoconstrictor assay （VCA）has been approved by FDA, but which is only applied?to glucocorticoid drugs. The bioequivalence of other topical preparations is evaluated through clinical end-point trials. FDA is still trying to explore other methods for bioavailability, such as tape stripping, dermal microdialysis, open flow perfusion and in vitro studies. The update of above methods is reviewed in this article.

Key words: topical dermatological drug products, bioavailability, bioequivalence