K K Jain MD (Dr. Jain is a consultant in neurology and has no relevant financial relationships to disclose.)
Originally released February 23, 1999; last updated February 8, 2020; expires February 8, 2023


Benzodiazepines are psychoactive drugs whose core chemical structure is the fusion of a benzene ring and a diazepine ring. The pharmacological target of benzodiazepines is GABA, the major inhibitory neurotransmitter in the central nervous system. The best-known drug of this series is diazepam, which is used as an anxiolytic, sedative-hypnotic, and anticonvulsant. Midazolam is used for preoperative sedation/anxiolysis with anterograde amnesia. Adverse effects include drowsiness and potential for addiction.

Key points


• Benzodiazepines have a better safety profile than barbiturates but are potentially addictive.


• Diazepam has been in clinical use for over half a century as an anxiolytic and antiepileptic agent.


• Midazolam is more potent than diazepam and is used to induce preoperative sedation/anxiolysis with anterograde amnesia.


• Nonbenzodiazepine agents are now preferred as hypnotic agents.

Historical note and terminology

Benzodiazepines are psychoactive drugs whose core chemical structure is the fusion of a benzene ring and a diazepine ring. The first benzodiazepine, chlordiazepoxide (Librium), was discovered in 1955 and became available for clinical use in 1960 (Sternbach 1972). Diazepam, the best-known benzodiazepine, was developed in the late 1950s and has been marketed as Valium since 1963. It was approved by the Food and Drug Administration in the United States prior to 1982 and is still 1 of the top 200 drugs. Although originally intended as an anxiolytic, it now has many other indications. Intravenous diazepam has been used since the 1960s for controlling status epilepticus (Otto and Schlagenhauf 1968). It is available in oral as well as parenteral forms, and a rectal gel was introduced in 1997.

A classification of benzodiazepines into various types based on chemical structure is as follows:


• 2-keto compounds: chlordiazepoxide, clorazepate, diazepam, flurazepam, halazepam, prazepam, and others.


• 3-hydroxy compounds: lorazepam, lormetazepam, oxazepam, temazepam.


• 7-nitro compounds: clonazepam, flunitrazepam, nimetazepam, nitrazepam.


• Triazolo compounds: adinazolam, alprazolam, estazolam, triazolam.


• Imidazo compounds: climazolam, loprazolam, midazolam.

After half a century of use, considerable information has accumulated about applications of benzodiazepines in neuropsychiatric disorders, other diseases, and anesthesia (Dell'osso and Lader 2013). Although some of their uses were empirical, benzodiazepines had a better safety profile than barbiturates. Now there is increasing awareness of the adverse effects of benzodiazepines, particularly addiction and drug abuse. Nevertheless, benzodiazepines are frequently prescriptions for short-term anxiety relief and some neurologic disorders. Benzodiazepines are now less popular than nonbenzodiazepines for treatment of insomnia. Nonbenzodiazepine hypnotics, which include zolpidem, zaleplon, and eszopiclone, have different molecular structures, but they act on the same benzodiazepine receptors and produce similar sedative effects.

This article will briefly review the clinical pharmacology of benzodiazepines, with a focus on diazepam, the most widely used benzodiazepine, as an example. Midazolam (Versed) will also be described.

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