Ethanol absorption across human skin measured by in vivo microdialysis technique

Microdialysis, a new bioanalytical sampling technique enables measurement of substances in the extracellular space. This initial study investigates the technique's usefulness in the field of percutaneous absorption of solvents, using ethanol as test substance. Microdialysis probes are equipped at the tip with a semi-permeable polycarbonate membrane which permits passive diffusion of substances. Ethanol does not damage the membrane. In vitro recovery for ethanol is good. Probes were inserted via a guide into the skin of the ventral forearm in 7 volunteers. 99.5% ethanol was applied to the skin in excess in a glass reservoir. The probe was perfused at a flow of 1 microliter/min. 50 microliters samples were analysed by gas chromatography. Absorption of ethanol was demonstrated in all subjects. Values from the 9 probes inserted ranged from 10 micrograms/ml to 800 micrograms/ml. The variation may be explained by inter-test or inter-individual variability in ethanol absorption. Individual metabolic capacity may be of importance. The method opens new possibilities in the investigation of skin barrier function in man.