Topical and bioavailability of benzoyl peroxide.

Synopsis Benzoyl peroxide has been used for over 20 years to treat youthful acne. The aim of this study is to determine its release rate from the vehicle that allows it to reach and treat the skin (topical availability) and its ability to pass through the skin and reach the general circulation (bioavailability), in order to bring about good topical availability, linked to bioavailability or, an 'abioavailability'. Three preparations containing 10% of benzoyl peroxide were administered to the back of shaven New Zealand rabbits. At day 0, day 5, day 12, day 19, day 26 and day 33, the topical effects were measured by cutaneous temperature, degree of erythema and the benzoic acid plasma record card, which shows blood sample results of the metabolism of the drug. The results obtained show that the topical availability of benzoyl peroxide coincides with a decrease in cutaneous temperature, after application in various dosage forms, in spite of the appearance of a marked erythema. The bioavailability is demonstrated by plasma benzoic acid evaluation. Before administration, benzoic acid levels are low but increase half an hour after administration, to reach a maximal level at 3 h. Benzoyl peroxide metabolizes quickly and does not seem to be able to cross the skin without being changed.