Kinetics of high-dose i.v. diazepam.

The pharmacokinetics of high-dose i.v. diazepam were studied in two patients in an intensive care unit. The first patient received up to 240 mg of diazepam daily for 21 days while the second received 60 mg daily for 30 days. Plasma concentrations of diazepam and its major metabolite, desmethyldiazepam, were very large but, despite severe underlying disease and simultaneous administration of several other drugs, the half-lives of diazepam and desmethyldiazepam washout were consistent with those found in healthy persons. Washout half-lives in the first patient were, if anything, shorter than expected, possibly caused by simultaneous administration of phenobarbitone. Thus the kinetics of diazepam are apparently not altered by administration of large doses.