Disulfiram and the ink cap mushroom

Mycetism, or mushroom poisoning, refers to the toxic effects of certain mushrooms. Of the world’s many thousands of mushroom species, fewer than 40 have been associated with fatalities, and around another 50 have been identified as containing significant levels of toxins. Some only cause symptoms when eaten raw, the toxins being denatured by heat, but due to similarities in the appearance of poisonous and non-poisonous varieties, it is recommended that mushrooms for food are collected only by experienced fungus gatherers.

Folk lore offers some (usually flawed) advice, such as avoiding fungi that are brightly coloured or have pointed caps or those that turn silver black on rubbing or turn rice red when boiled.

The common ink cap mushroom (Coprinopsis atramentaria) is unusual in that it is not toxic when eaten on its own but causes symptoms of toxicity if alcohol is consumed following its ingestion — hence its synonym of tippler’s bane.

Its unusual toxic profile is due to a cyclopropylglutamine compound called coprine (N5-1-hydroxycyclopropyl-L-glutamine), which itself has no intrinsic toxicity but acts as a protoxin. Coprine is metabolised to

1-aminocyclopropanol, which inhibits the enzyme aldehyde dehydrogenase (ALDH), responsible for the catalysis of aldehydes to acetic acid. Alcohol consumption is followed by a build-up of an intermediate ethanol metabolite, acetaldehyde, which is responsible for most of the symptoms of a hangover, and coprine exacerbates its effects.

This process is the same as that produced by disulfiram, and the symptoms are identical to those described in reactions to disulfiram, such as facial reddening, nausea, vomiting, palpitations, malaise and agitation. The ALDH inhibition usually lasts three days but can persist for five. Alcohol consumption up to three days after ingesting ink caps can still cause toxic effects.

There have been no known fatalities following coprine and alcohol poisoning, but treatment involves monitoring for cardiac arrhythmias and hypotension, as well as rehydration therapy, and reassurance that the unpleasant symptoms will pass.