Distribution and dissociation of benzoyl peroxide in cutaneous tissue after application on skin in the hairless rat

Abstract

Synopsis The distribution and dissociation of 14C-benzoyl-peroxide were studied in the skin of hairless rats after the application of a 10% gel during 3, 8 and 24 h. The distribution was appraised in the stripped horny layer and in the epidermis, and the dermis cut in slices parallel to the cutaneous surface. The conversion of benzoyl peroxide (b.p.) to benzoic acid (b.a.) was investigated from extracts of these different cutaneous layers by thin layer chromatography (TLC). The greatest amount of penetrating b.p. (9 to 14% of the applied dose) was found in the horny layer, which forms a reservoir and where biotransformations were reduced. Small quantities of b.p. diffused toward the epidermis down to the deeper dermis, where b.a. represented 74% of the radioactivity. Distribution gradients of the radioactivity and conversion rates to b.a. were stable between 3 and 24 h of application in all parts of the skin. This result showed that diffusion of b.p. from the vehicle was in balance with the dissociation processes and the blood resorption as b.a., throughout the experiment.