Effects of l-Menthol and dl-Camphor on the Penetration and Hydrolysis of Methyl Salicylate in Hairless Mouse Skin.

Plasters containing methyl salicylate with and without l-menthol and dl-camphor were prepared and topically applied on hairless mouse skin to investigate the effects of l-menthol and dl-camphor on the skin penetration and hydrolysis of methyl salicylate in the skin. The in vitro hydrolysis of methyl salicylate was also investigated using the skin homogenate. It was found that l-menthol with dl-camphor enhanced the skin penetration of methyl salicylate, and they inhibited both the in vivo and in vitro hydrolysis of methyl salicylate to salicylic acid.