Clorazepate kinetics in treated epileptics.

Clorazepate is decarboxylated to form desmethyldiazepam and is a convenient way of administering it. Its kinetics were investigated in epileptic patients after single oral and multiple oral doses. Peak serum concentrations of demethyldiazepam occurred in 0.5 to 1 hr. There appeared to be a brief lag before rapid absorption. Because of the rapid absorption with resulting high serum levels, daily doses should be divided. Serum concentration/time curves were best fitted by the two-compartment open model. The apparent t1/2 of the distribution phase was 1.28 +/- 0.44 hr and the t1/2 of the disposition phase was 40.8 +/- 9.96 hr. Serum concentrations rose after meals. Whole body apparent volume of distribution (VB/F) was 1.63 +/- 0.24 L/kg. Total plasma clearance was 34.4 +/- 7.2 ml/min, which is greater than clearance levels for desmethyldiazepam in normals and reflects the greater hepatic metabolism which occurs in treated epileptics. The discrepancy illustrates the hazards of extrapolating data collected in normals to patients with multiple drug exposures.