CHAPTER 16: Benzodiazepines

Benzodiazepines are normally seen as pharmaceutically-manufactured tablets, capsules and occasionally as injectable solutions. They differ in their substitution pattern on the basic molecular skeleton (3H-1,4-benzodiazepine). They act as depressants of the central nervous system (CNS) and are widely used in medicine to treat anxiety and insomnia. Benzodiazepines facilitate the binding of the inhibitory neurotransmitter γ-aminobutyric acid (GABA) at various receptors in the CNS. Chlordiazepoxide (Librium®) was the first to be synthesised in 1957 and introduced into medicine in 1961. Diazepam (Valium®) is one of the most widely-prescribed benzodiazepines. International control of benzodiazepines by means of the United Nations (UN) Convention on Psychotropic Substances, 1971 was introduced over 35 years ago. By 2021 there were 41 benzodiazepines listed in that Convention. Apart from flunitrazepam which is in Schedule III, all are in Schedule IV. However, following the appearance in recent years of many so-called designer benzodiazepines, a further 16 were added to the United Kingdom Misuse of Drugs Act in 2017 again as Class C controlled drugs. Some of these novel substances were licensed medicines in other countries. In 2020, the ACMD recommended that three more benzodiazepines should be added to the MDAct as Class C drugs. A number of other benzodiazepines have been reported to the European Monitoring Centre for Drugs and Drug Addiction that are neither controlled in the UK nor listed in the UN 1971 Convention.