A large-sample study of diazepam pharmacokinetics

Ther Drug Monit. 1989 Nov;11(6):652-7. doi: 10.1097/00007691-198911000-00007.


Healthy male volunteers (n = 48) aged 18-44 years received a single 10-mg oral dose of diazepam. Plasma diazepam and desmethyldiazepam concentrations were measured at multiple points during the next 11 days. The distribution of peak plasma concentration (mean, 406 ng/ml) was not skewed and did not differ significantly from normal (Guassian). However, the distributions of elimination half-life (44.2 h), elimination rate constant (0.0219/h), clearance (26.6 ml/min), and volume of distribution (83 L) all were significantly skewed and deviated significantly fron normal. After logarithmic transformation, the distributions of elimination rate constant, elimination half-life, and volume of distribution were consistent with normal; however, this was not the case for time of peak plasma concentration. Thus, the pharmacokinetic characteristics of oral diazepam are highly variable even in a relatively homogeneous population. Parametric statistical testing procedures and pharmacokinetic forecasting schemes may be improved by more precise delineation of the underlying distributions for pharmacokinetic variables.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adolescent
  • Adult
  • Body Weight
  • Chromatography, Gas
  • Diazepam / pharmacokinetics*
  • Half-Life
  • Humans
  • Male
  • Nordazepam / blood


  • Nordazepam
  • Diazepam