Diurnal rhythms of aminopyrine metabolism: failure to sleep deprivation to affect them.

After a single oral dose of aminopyrine (9 mg/kg), mean salivary aminopyrine half-lives (t 1/2s) and metabolic clearance rates in 12 normal male volunteers exhibited diurnal variations. Salivary aminopyrine t 1/2s were approximately 50% longer at 8 P.M. (2.1 +/- 0.7 hr) than at 8 A.M. (1.4 +/- 0.3 hr). Mean aminopyrine metabolic clearance rates decreased 20% from 8 A.M. (418.2 +/- 152.0 ml/min) to 8 P.M. (335.3 +/- 107.6 ml/min). There were large interindividual variations in the magnitude of these diurnal changes in aminopyrine t 1/2 and metabolic clearance rates. There were nonsignificant changes in mean aminopyrine apparent volumes of distribution (aVd) which increased only slightly from 53.1 +/- 20.6 L at 8 A.M. to 59.7 +/- 26.5 L at 8 P.M. There were diurnal variations in plasma 11-hydroxycorticosteroids (11-OHCS), mean values of which decreased 60% from 16.2 +/- 4.2 microgram/100 ml at 8 A.M. to 6.5 +/- 1.9 microgram/100 ml at 8 P.M. Sleeplessness for 24 or 48 hr under the conditions of this experiment failed to affect diurnal rhythms in aminopyrine metabolism or plasma 11-OHCS concentrations.