PERCUTANEOUS-ABSORPTION OF SUNSCREEN AGENTS FROM LIQUID PARAFFIN - SELF-ASSOCIATION OF OCTYL SALICYLATE AND EFFECTS ON SKIN FLUX

This study provides an investigation of the availability of octyl sali cylate (OS), a common sunscreen agent, from liquid paraffin and the ef fect of OS on skin permeability. A model membrane system to isolate th e vehicle effect from membrane permeability has been developed. Partit ioning of OS between liquid paraffin and aqueous receptor phases was c onducted. Partition coefficients increased with increase in OS concent ration. A range of OS concentrations in liquid paraffin was diffused a cross human epidermis and synthetic membranes into 4% bovine serum alb umin in phosphate-buffered saline and 50% ethanol. Absorption profiles of OS obtained from silicone and low-density polyethylene (LDPE) memb ranes were similar to each other but higher than for the high-density polyethylene [HDPE (3 times)] membrane and human epidermis (15 times). The steady state fluxes and apparent permeability coefficients (K-p') obtained from the diffusion studies showed the same trends with all m embranes, except for the HDPE membrane which showed greater increase i n flux and K-p' at concentrations above 30%. IR spectra showed that se veral bands of OS were shifted with concentrations, and the molecular models further suggested that the main contribution to the self-associ ation is from non-1,4 van der Waals interactions.