SURFACTANT EFFECTS IN PERCUTANEOUS-ABSORPTION .1. EFFECTS ON THE TRANSDERMAL FLUX OF METHYL NICOTINATE

We have investigated the effects of a series of surfactants on the permeability of human skin in vitro using methyl nicotinate as a model drug. The surfactants used were cetyl trimethyl ammonium bromide, sodium lauryl sulphate, decyl methyl sulphoxide and Brij 36T. These surfactants have a linear alkyl chain of 10-12 units linked to different hydrophilic groups. We found that while the ionic surfactant exerted a greater effect on the flux of methyl nicotinate, the nonionic surfactants had a smaller but more immediate effect on the flux. This is consistent with the hypothesis that for compounds to disturb the permeability barrier of the stratum corneum they must first penetrate it themselves. Ionic compounds can be expected to penetrate this lipophilic barrier more slowly than nonionic compounds of a similar structure and therefore will take longer to elicit their effects.