In vitro human epidermal and polyethylene membrane penetration and retention of the sunscreen benzophenone-3 from a range of solvents

Purpose. To study epidermal and polyethylene membrane penetration and reten tion of the sunscreen benzophenone-3 (BP) from a range of single solvent ve hicles and evaluate solvent effects on permeability parameters. Methods. Th e solubility of BP was measured in a number of solvents. Penetration of BP across human epidermis and high density polyethylene (HDPE) membranes was s tudied from 50% saturated solutions in each solvent. Results. Maximal BP fl uxes from the solvents across the two membranes varied widely. Highest flux es were observed from 90% ethanol (EtOH) for epidermis and from isopropyl m yristate (IPM) and C12-15 benzoate alcohols (C12-15 BA) for HDPE membrane. Both the flux and estimated permeability coefficient and skin-vehicle parti tioning of BP appeared to be related to the vehicle solubility parameter (d elta(v)). The major effects of solvents on BP flux appear to be via changes in BP diffusivity through the membranes. Conclusions. Minimal penetration of sunscreens such as BP is best achieved by choosing vehicles with a delta (v) substantially different to the solubility parameter of the membrane.