Abstract

Absorption and plasma concentrations of transdermally delivered drugs may be increased during heat exposure. We studied the effects of short-term heat exposure in a sauna bath on the pharmacokinetics of transdermal nicotine, 25 mg/16 hr, in 12 healthy smokers in an open, randomized crossover study that consisted of a control session and a sauna bathing session. In the sauna session the subjects stayed seated in a sauna bath (mean temperature 82 degrees C (180 degrees F); mean relative humidity 28%) for three 10-minute periods separated by two 5-minute breaks. Sauna bathing significantly (p < 0.01 versus control) increased peak plasma concentration, area under the plasma concentration-time curve from 0 to 1 hour, the amount of nicotine absorbed, and the mean plasma nicotine concentrations during heat exposure. No significant difference in nicotine area under the plasma concentration-time curve from 0 to 3 hours was observed. In addition, the combined effects of transdermal nicotine and sauna bathing on hemodynamics, some psychomotor skills, and subjective symptoms were evaluated. We concluded that absorption and plasma concentrations of transdermally delivered nicotine may be increased during exposure to high ambient temperature, probably because of enhanced skin blood flow. However, no adverse symptoms were recorded.