Chronopharmacokinetics of ethanol. II. Circadian rhythm in rate of blood level decline in a single subject.

A male human subject administered single, oral doses of ethanol was examined repeatedly for venous ethanol levels. Four separate trials, begun at 03.00, 09.00, 15.00, and 21.00 h, on different days yielded four different estimates of the slope of the apparently linear ethanol disappearance curve. The slopes appeared to exhibit circadian rhythmicity. In a second study of the same subject, the slope was estimated 7 times over a period of 26 h following repeated oral doses. These slopes also appeared to vary in a daily fashion. These preliminary results suggest that pharmacokinetic parameters may not be invariable with time of day.