Effect of 2-hydroxypropyl-beta-cyclodextrin on percutaneous absorption of methyl paraben

A potential use of 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CyD) to solubilize methyl paraben and to suppress its percutaneous absorption was examined, and compared with nonionic surfactant HCO-60. HP-beta-CyD significantly increased the solubility of methyl paraben in water, where the apparent 1:1 stability constant of the soluble complex was determined to be 2150 M-1. The in-vitro cutaneous permeability of methyl paraben through an isolated skin of hairless mouse was suppressed by HP-beta-CyD, thus promoting the bioconversion of methyl paraben to the less toxic metabolite, p-hydroxybenzoic acid (p-HBA) in the epidermis. These effects of HP-beta-CyD were greater than those of HCO-60. HP-beta-CyD (2% w/v) reduced the in-vivo percutaneous absorption of methyl paraben by 66% 24 h after the topical application of a solution containing [14C]methyl paraben to hairless mouse skin. Additionally, the percutaneous absorption of [14C]HP-beta-CyD was confirmed to be extremely low. These results suggest that HP-beta-CyD is useful in liquid preparations of methyl paraben for topical application.