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Toxic — not for home useThe seeds are highly poisonous. Robert Christison ate part of one in 1855 and documented the effects; 19th-century researchers found muscular paralysis to be the cardinal feature of poisoning, which they treated with atropine. Fatal in the Calabar ordeal.In an emergency, call your local emergency number or poison centre.

Calabar bean

Physostigma venenosum

Also calledOrdeal bean of Old Calabar · Chop nut (Old Calabar, trial by ordeal)

A West African climbing legume whose seeds were given in trials by ordeal in Old Calabar (south-eastern Nigeria) to decide guilt or innocence. Scottish doctors studied the beans in the 1850s–60s and isolated physostigmine, the first drug that constricts the pupil, the first known cholinesterase inhibitor, and an antidote still used for anticholinergic poisoning. The bean itself is deadly and has no place in home use.

What it is used for

Poisoning (antidotes)
Strong
Physostigmine reverses the anticholinergic (antimuscarinic) toxidrome, used in hospital since an 1864 case of atropine poisoning in Prague. In a small blinded trial in adolescents (19 patients), it controlled delirium better than lorazepam (delirium after 4-hour infusion 22% vs 100%) without serious adverse events; in an 815-patient US toxicology registry, patients given physostigmine alone were intubated less often.^2,3,4
Eyes
Moderate
Calabar bean extract was the first agent shown to constrict the pupil (Argyll Robertson, 1863), and physostigmine, isolated in 1862, began the history of glaucoma drugs. It has since been replaced by newer glaucoma medicines.^2,5

Safety

Pregnancy: Contraindicated
Breastfeeding: Contraindicated
Children: Not for any home use. Physostigmine is given only in hospital under monitoring.

Interactions with medicines

atropine and other antimuscarinic drugsMajorPhysostigmine and atropine are mutually antagonistic; atropine is the standard treatment for poisoning by physostigmine and other cholinesterase inhibitors.

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Do not use if

Any self-administration of the seeds or extracts

Side effects

Clinicians use physostigmine cautiously because of concern about its safety and short duration of action

In the healing traditions

African traditional medicine
Chop nut (ordeal bean)
Not a remedy but a judicial ordeal in Old Calabar: the seeds were believed to have the power to show whether a person accused of a serious misdemeanour was innocent or guilty. Missionaries who arrived in 1846 estimated about 120 deaths a year from it.
Modern pharmacology
Physostigmine
Reversible cholinesterase inhibitor; used for antimuscarinic poisoning and formerly for glaucoma; studied as an adjunct in septic shock. Fraser's experiments on physostigmine–atropine antagonism in the 1870s laid groundwork for the atropine doses still used against cholinesterase-inhibitor poisoning.

Active compounds

physostigmine: tertiary-amine alkaloid, quantitatively the most important of three active alkaloids in the bean; tertiary amine and reversible cholinesterase inhibitor

History

Mid-19th-century missionaries in Old Calabar sent beans to Scotland, where Christison tested them on himself in 1855 and Balfour named the plant Physostigma venenosum in 1861. Thomas Fraser's 1862 Edinburgh thesis described their systemic effects, and in 1863 the ophthalmologist Argyll Robertson, alerted by Fraser, announced the first drug to constrict the pupil.

Sources

Reference, not prescription. Nothing here is medical advice. Herbs can interact with medicines and be dangerous in pregnancy; tell your doctor or pharmacist about anything you take.