Influence of lipids on the mannitol flux during transdermal iontophoresis in vitro

The aim of the present study was to evaluate the influence of the Lipids EP C (L-alpha-phosphatidylcholine, egg lecithin), DSPC (distearoylphosphatidyl choline), and SA (stearylamine) on the iontophoretic mannitol transport thr ough human skin in vitro. The skin was pretreated with 1 mM Lipid suspensio n with ethanol (32%) for 24 h prior to the iontophoretic experiment with ma nnitol. In addition, the penetration of fluorescent Lipids into the epiderm is during the pretreatment was studied by confocal laser scanning microscop y (CLSM). The results of the present study show that pretreatment of the sk in with zwitterionic EPC increases the iontophoretic transdermal mannitol f lux about three-fold compared to iontophoretic control without pretreatment . However, skin pretreatment with another zwitterionic phospholipid, DSPC, did not influence the iontophoretic flux of mannitol. In contrast, pretreat ment of the skin with cationic SA decreased the iontophoretic mannitol flow from the anode. It is concluded that EPC works as a penetration enhancer f urther increasing the transdermal mannitol flux during iontophoresis. In co ntrast, the cationic stearylamine changes the charge of the skin, thus lead ing to decreased electroosmosis and decreased mannitol flux. Hence, the eff ects of stearylamine are assumed to be mediated by the alterations in the c harge of the stratum corneum structures, while EPC is suggested to decrease the permeability barrier of the skin. (C) 2000 Elsevier Science B.V. All r ights reserved.