Percutaneous Absorption of Butylparaben in Vitro. II. Effects of Micellar Trapping of the Drug and Percutaneous Absorption of Nonionic Surfactants

The effect of surfactants on the percutaneous absorption of butylparaben from micellar solution was studied. Percutaneous absorption of butylparaben from aqueous solution containing the critical micellar concentration (cmc) of a surfactant was measured in order to determine the contribution of the free butylparaben. Percutaneous absorption of polysorbate 80 and octaethyleneglycol dodecyl ether was also measured in order to evaluate the effect of absorption of micelles, if any. The results indicated that the surfactants were scarcely absorbed, but the free concentration of butylparaben could not account for the total drug absorption from micellar solution. However, the amount of surfactant absorbed increased with increase in the surfactant concentration above the cmc, indicating that surfactant molecules in micelles could be absorbed. This suggests that some of the micelles were adsorbed and/or dissociated on the skin surface, so that the effective concentration of surfactant as well as that of butylparaben for percutaneous absorption would be increased.