LAUSR

This study reports the effect of surfactant charge and concentration on the permeation of four model compounds (benzocaine, benzotriazole, ibuprofen and lidocaine). Surfactant charge was systematically varied using a range of surfactants that are known to possess specific head group charges, namely an anionic, a cationic, a zwitterionic and a neutral form over a series of surfactant concentrations, i.e. where possible, both above, and below, the critical micellar concentration for each surfactant. It was found that there was almost always a systematic reduction in permeation as the concentration of surfactant increased despite the wide range of physicochemical properties exhibited by the four model compounds studied. Overall, it was concluded that the presence of surfactant does generally seem to reduce permeation, regardless of the compound in question, and that the effect is surfactant concentration, as well as charge, dependent.