Category:Benzodiazepines: Difference between revisions

The benzodiazepines are a class of medicines used chiefly for anxiety, insomnia, seizures, and muscle spasm. For a time in the 1970s they were the most widely prescribed drugs in the world. Their history is a particularly clear example of a recurring pattern in the history of medicine: a new drug is introduced as the safe answer to the dangers of an older one, is prescribed enormously, and only later is understood to carry serious risks of its own.

The first benzodiazepine was found by accident. In the mid-1950s the chemist Leo Sternbach, working for Hoffmann-La Roche in Nutley, New Jersey, was searching for new tranquilizers and chose to revisit a group of compounds he had worked with decades earlier as a young researcher in Poland. Sternbach was a Polish-Jewish chemist whom the company had helped flee Europe in 1941.^[1]

The compounds were disappointing, and the project was set aside. In 1957, during a laboratory clean-up, a colleague noticed a crystalline compound left over from the abandoned work that had never been tested. It was submitted for routine animal testing, largely so that the chemistry could be published, and, unexpectedly, it showed strong sedative, muscle-relaxant, and anticonvulsant effects.^[1] Chemical analysis showed the compound had rearranged into a structure different from what Sternbach had assumed: a new class, the benzodiazepines. It was named chlordiazepoxide.

Chlordiazepoxide was introduced in 1960 under the brand name Librium, and diazepam followed in 1963 as Valium. The two were, for a time, among the most commercially successful drugs ever sold.^[1] Their rise was rapid and very large: by the mid-to-late 1970s the benzodiazepines headed the lists of most-prescribed medicines, and diazepam in particular became a cultural touchstone, the "mother's little helper" of a 1966 Rolling Stones song.^[2]

A central reason for their success was their apparent safety relative to what came before. The benzodiazepines displaced the barbiturates and older tranquilizers such as meprobamate; compared with the barbiturates in particular, they were much less likely to cause fatal respiratory depression in overdose.^[2] This was a genuine advance. But the benzodiazepines, the barbiturates, and alcohol all act on the same broad system in the brain, and the assumption that the new drugs were largely free of the dependence problems of the old ones proved to be mistaken.

Concern grew gradually. Through the 1960s and 1970s benzodiazepines were prescribed freely and often for long periods. By the early 1980s, controlled studies, notably by Malcolm Lader, Peter Tyrer, and others, established that people taking benzodiazepines at ordinary therapeutic doses could become physically dependent, experiencing a genuine withdrawal syndrome when they stopped.^[3] The withdrawal could be prolonged and difficult, and patient groups, especially in the United Kingdom, became vocal about harms they felt had not been disclosed.

The reckoning had a notable legal dimension: the benzodiazepines became the subject of what has been described as the largest class-action lawsuit in UK history, brought on behalf of thousands of patients who alleged that manufacturers had been aware of the dependence risk.^[4] The clinician C. Heather Ashton became widely known for her work supporting people withdrawing from benzodiazepines; the withdrawal guidance she wrote, generally known as the Ashton Manual, remains a widely cited resource.^[5]

Benzodiazepines remain genuinely useful medicines, with clear roles in the short-term treatment of severe anxiety, in certain seizures, in alcohol withdrawal, and in anesthesia. But prescribing guidance has shifted substantially toward caution: short courses, the lowest effective dose, and planned tapering rather than abrupt cessation, which can itself be dangerous.^[2] In many countries they are no longer regarded as first-line treatment for anxiety or insomnia.^[6]

A particular modern concern is the combination of benzodiazepines with opioids. Because both depress the central nervous system, taken together they considerably increase the risk of fatal respiratory depression; a large share of opioid overdose deaths have also involved benzodiazepines. In the United States, regulators added a boxed warning against co-prescribing the two classes in 2016, and in 2020 strengthened the benzodiazepine class warning to address abuse, dependence, and withdrawal directly.^[7]

Benzodiazepines are understood to act at the GABA-A receptor, the receptor for the brain's principal inhibitory neurotransmitter, gamma-aminobutyric acid (GABA). They bind at a site on the receptor distinct from where GABA itself binds, and act as positive modulators, they do not activate the receptor on their own, but increase the effect of GABA when it is present, enhancing inhibition in the nervous system.^[5] Different subtypes of the receptor are associated with different effects, broadly, sedative, anxiety-reducing, and anticonvulsant, though the mapping is not simple. That benzodiazepines bind and modulate the GABA-A receptor is well established; the fuller relationship between this action and the full range of effects, and in particular the mechanism by which tolerance and dependence develop, is more complex and remains a subject of research.

The benzodiazepines include diazepam, chlordiazepoxide, lorazepam, alprazolam, clonazepam, temazepam, nitrazepam, oxazepam, midazolam, and flurazepam, among many others. Closely related are the non-benzodiazepine "Z-drugs" such as zolpidem, which act at the same receptor and share many of the same properties despite a different chemical structure. Flumazenil is a benzodiazepine antagonist, it blocks the receptor and can reverse benzodiazepine effects. The list is not exhaustive.

Taken alone in overdose, benzodiazepines are considerably less dangerous than the barbiturates they replaced, which was central to their original appeal. Their principal hazards are otherwise. Common effects include drowsiness, sedation, and impairment of memory and coordination; in older adults they are associated with falls, fractures, and confusion. Regular use over even a few weeks can lead to tolerance and to physical dependence, with a withdrawal syndrome, which can include anxiety, insomnia, and, in serious cases, seizures, on stopping; for this reason benzodiazepines are generally tapered gradually rather than stopped abruptly. The danger in overdose rises sharply when benzodiazepines are combined with other central nervous system depressants, particularly opioids and alcohol. Figures for these risks are population estimates that vary between studies, and individual response varies considerably between people.