The bioavailability of dermatological and other topically administered drugs.

The literature addressing determination of the bioavailability of dermatological and other topically administered drugs has been reviewed. The various methods employed, their advantages and drawbacks, have been identified and evaluated. The state of the art and the success of topical bioavailability assessment are discussed in the light of the information presented. It is concluded that, although current methodology ensures the responsible use of topical medicaments, the techniques are, on the whole, quantitatively inadequate. A number of recommendations are proposed as possible improvements to the approaches now undertaken, and specific measurements for drugs in different therapeutic categories are suggested. The ultimate objective of this survey is to catalyze the establishment of straightforward, objective, quantitative, and reproducible methods to evaluate topical bioavailability and to reduce significantly, thereby, the incidence of bioinequivalence and pharmacological inactivity observed following drug dosing to the skin.