Pharmacokinetics of diazepam in epileptic patients and normal volunteers following intravenous administration.

1 The pharmacokinetics of diazepam following intravenous administration have been investigated in six normal volunteers and nine epileptic patients receiving chronic antiepileptic drug therapy. 2 After intravenous administration, serum diazepam levels declined biexponentially in all subjects. The elimination half-life was significantly shorter and the plasma clearance significantly higher in the patients than in the normal volunteers. 3 Serum N-desmethyldiazepam levels were higher and the time to peak serum concentration was earlier in the epileptic patients than in the controls. 4 It is suggested that the metabolism of diazepam is induced in patients treated with enzyme inducing antiepileptic drugs, although a protein binding interaction between valproic acid and diazepam may contribute to the higher plasma clearance in the epileptic patients taking sodium valproate.