Benzodiazepines: a summary of pharmacokinetic properties

Br J Clin Pharmacol. 1981;11 Suppl 1(Suppl 1):11S-16S. doi: 10.1111/j.1365-2125.1981.tb01833.x.


1 The onset and duration of action of benzodiazepines after single oral doses depend largely on absorption rate and extent of distribution, respectively. 2 The rate and extent of accumulation during multiple dosage depend on elimination half-life and clearance. A framework is proposed for classification of benzodiazepines according to elimination half-life. 3 Long-acting benzodiazepines have half-life values usually exceeding 24 hours. Drugs in this category have long-acting pharmacologically active metabolites (often desmethyldiazepam), accumulate extensively during multiple dosage, and may have impaired clearance in the elderly and those with liver disease. 4 Intermediate and short-acting benzodiazepines have half-life values from 5-24 hours. Active metabolites are uncommon. Accumulation during multiple dosage is less extensive than with the long-acting group, and diminishes as the half-life becomes shorter. Age and liver disease have a small influence on metabolic clearance. 5 The half-life of ultrashort acting benzodiazepines is less than 5 hours. These drugs are essentially non-accumulating. 6 Pharmacokinetic classification may assist in understanding of differences among benzodiazepines, but does not explain all of their clinical actions.

Publication types

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

MeSH terms

  • Anti-Anxiety Agents / administration & dosage
  • Anti-Anxiety Agents / classification
  • Anti-Anxiety Agents / metabolism*
  • Benzodiazepines
  • Biotransformation
  • Half-Life
  • Humans
  • Intestinal Absorption
  • Kinetics


  • Anti-Anxiety Agents
  • Benzodiazepines