Percutaneous absorption and metabolism of 2-butoxyethanol in human volunteers: a microdialysis study

We determined percutaneous absorption kinetics of 2-butoxyethanol (BE) in volunteers using microdialysis. Four male volunteers were dermally exposed twice to 90% and 50% aqueous solutions (v/v) of BE for 4.5h. To determine percutaneous absorption kinetics the concentration of BE was measured in the dialysate samples collected at 30 min-intervals throughout exposure. The systemic absorption, which is needed to determine recovery of the BE in the dialysate, was estimated from the concentration of the main metabolite of BE, free butoxyacetic acid (BAA) in urine. A pseudo steady-state percutaneous absorption was reached approximately at 2h of exposure for both BE concentrations. The maximum dermal flux of 50% BE was higher than that of 90% BE (2.8+/-0.4, 1.9+/-0.6 mg cm(-2)h(-1), respectively). The more diluted BE solution showed shorter lag time: 25 min versus 39 min. The amount of BAA was determined in the pooled dialysate samples collected at 4 and 4.5h. The dermal metabolism seems to be low, the BAA amount ranged from 0.03% to 1.9% of the BE in the same dialysate. Our study demonstrates applicability of microdialysis technique for assessment of percutaneous absorption kinetics and dermal metabolism without interference from the systemic compartment.