Abstract
Percutaneous penetration of 14C-butylparaben (BP) from a liposome suspension was studied in vitro using a flow-through type diffusion chamber. The amount of 14C-BP that penetrated through the skin of guinea pigs from liposome suspension decreased as the lipid content increased. This suggested that BP in the outer aqueous phase mainly contributed to the percutaneous penetration. However, 14C-BP in liposomes was also demonstrated to participate in the penetration to a small extent. Mathematical analysis based on diffusion theory supported these findings.Substantial entrapment of BP in liposomes was maintained during the period of the in vitro experiment (30 h), indicating that the free concentration of BP would be maintained in the donor region after the application of the liposome formulation to it. Furthermore, liposomes induced neither alteration of the barrier function of the stratum corneum nor denaturation of skin proteins in vitro. These findings are consistent with a contribution of direct BP absorption from liposomes at the skin surface.
