Potential mechanisms by which a single drink of alcohol can increase transdermal absorption of topically applied chemicals

Background: Both chronic and acute ethanol consumption increase transdermal penetration of topically applied xenobiotics. The mechanisms by which this enhancement occurs are unknown. We hypothesized that either the vasodilatory effects of ethanol or its ability to disrupt the lipid bilayer via lipid peroxidation, may be contributing to the increased transdermal absorption observed in alcohol consuming animals. Methods: Male Wistar rats were gavaged with 1.5, 3, 4.3, 6 or 10 g/kg ethanol or saline control or were treated with either the vasoconstrictor epinephrine or with the vasodilator prilocaine. Dermal blood flow, transepidermal water loss (TEYvL), and skin moisture were non-invasively measured. Transdermal penetration was then determined for four xenobiotics (paraquat, dimethyl formamide (DMF), 2,4-dichlorophenoxyacetic acid (2,4-D) and NN-diethyl-m-toluamide (DEET)). Lipid peroxidation was also determined by monitoring the formation of malondialdehyde. Results: Dermal blood flow increased by approximately 27% (p < 0.05), TEWL increased 1.12 +/- 0.2-fold while skin lipid peroxidation increased 1.4-fold (p < 0.05) 2 h after gavage with 10 g/kg alcohol. Transdermal penetration of paraquat was increased by prilocaine (ER = 2.1 +/- 0.4, p < 0.05), but the absorption of DEET, 2,4-D and DMF were not influenced by greater blood flow. Reducing dermal blood flow with epinephrine did not cause any significant changes in transdermal penetration. Conclusions: Vasodilation triggered by a single episode of ethanol ingestion is not responsible for the observed increase in transdermal absorption. Ethanol induced changes in lipid peroxidation and TEWL demonstrate that drinking alcohol induces transdermal absorption of xenobiotics. (c) 2007 Elsevier Ireland Ltd. All rights reserved.