Improved delivery through biological membranes XD: Percutaneous absorption and metabolism of methylsulfinylmethyl 2-acetoxybenzoate and related aspirin prodrugs.

Oxidative-reductive interconversion of the methylthiomethyl ester of aspirin and the corresponding sulfoxide and sulfone derivatives can be detected in rat liver homogenate, in addition to the extremely facile hydrolysis of these esters. The methylthiomethyl and methylsulfinylmethyl 2-acetoxybenzoates penetrate freshly excised hairless mice skin rather easily with the simultaneous hydrolysis of the two ester functions. Contrary to in vivo observations in dogs, where significant amounts of aspirin formed, the prodrugs cleave to salicylic acid and/or salicylate esters rather than aspirin.