PsychoTropical Research - Dr Ken Gillman, Serotonin Syndrome, Mirtazapine, Dual Action Drugs. Benzodiazepines - Toxicity.

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Benzodiazepines - Toxicity

Benzodiazepines - Toxicity

Date Created: 13/09/1999   Last Modified: 11/10/1999   Last Checked: 21/10/2002

The old barbiturates are more toxic than are the benzodiazepines; there were more than 100 deaths for every million scripts with barbiturates, compared to about 3 deaths for every million scripts with anxiolytic benzodiazepines and 9 for every million scripts with hypnotic benzodiazepines; approximately a twenty-fold lessening in mortality.

That is a relatively large change; but how do benzodiazepines compare with other currently used drugs? Looking at UK totals of deaths from overdose in the 1980s (rather than deaths per million scripts) gives the following perspective:--

Deaths
Distalgesic 2479
Paracetamol 2002
benzodiazepines 1576
Aspirin 1308
amitriptyline 1083
dothiepin 981

Relative to the antidepressants as a group the most toxic benzodiazepines (flurazepam and temazepam) probably have more deaths (per million scripts) than the least toxic of the old TCAs, as indicated by the best figures so far available.

Relative toxicity among the different benzodiazepines / anxiolytics

High FTI
flurazepam; 20 deaths for every million scripts
temazepam; 12 deaths for every million scripts

Intermediate FTI
triazolam 5 deaths for every million scripts
nitrazepam 4 deaths for every million scripts

Low FTI
diazepam 3.5 deaths for every million scripts
lorazepam 2 deaths for every million scripts
oxazepam 3 deaths for every million scripts
zopiclone 3 deaths for every million scripts
buspirone 0 deaths for every million scripts

The most likely explanation for the differences in FTIs of benzodiazepines is their inherent toxicity not their degree of sedative effect.

Note especially that chlormethiazole and chloral hydrate have very high FTIs (almost 100 for every million scripts).

It is also worth noting that of the barbiturates phenobartitone is by far the least toxic at 21 deaths for every million scripts (worst is barbitone at 6000, the average for barbiturates is 75).