Describe datura poisoning with its medicolegal importance.

Source and Mechanism

• Datura stramonium and D. Metel — dhatura, thorn apple, devil’s trumpet, kala dhatura — is a common weed throughout India with a spiny capsular fruit containing numerous brown-black seeds resembling those of chilli, which is how it is added to food unnoticed
• Alkaloids — hyoscine (scopolamine), hyoscyamine and atropine; all parts are toxic, and the seeds are the most poisonous. Fatal dose about 50 to 100 seeds, or 60 to 100 mg of the alkaloid
• Mechanism — competitive antagonism at muscarinic acetylcholine receptors, peripherally and centrally — the exact opposite of organophosphate poisoning, which is a useful way to hold the two together

Medicolegal Importance

• Datura is the classical "road poison" or "railway poison" of India, used to stupefy travellers for the purpose of robbery. The seeds are mixed into food, tea or sweets offered by a friendly fellow-passenger; the victim becomes confused and amnesic and is robbed, and often has NO memory of the events. The charge is under BNS 123 (formerly IPC 328), causing hurt by means of a stupefying substance
• Other uses — suicidal and accidental, the latter particularly in children eating the attractive fruit, and from confusion of the seeds with chilli seeds or with edible seeds; abuse for its hallucinogenic effects by adolescents; as a cattle poison; and it is said to have been used to stupefy young women for the purposes of trafficking and sexual assault
• Postmortem — there is no characteristic finding; the pupils may be dilated, the mucous membranes dry, and seeds may be recovered from the stomach and intestine and identified botanically, which is the most valuable evidence. The mydriatic test — an extract of the stomach contents instilled into the eye of a cat or rabbit dilates the pupil — is the classical confirmatory test

Treatment and Applied Aspects

• Gastric lavage and activated charcoal, which is effective and may be repeated since gastric emptying is delayed; and the removal of seeds, which may remain in the stomach for a long time for the same reason
• Physostigmine is the specific antidote — a tertiary amine anticholinesterase which crosses the blood-brain barrier and therefore reverses the central as well as the peripheral effects, unlike neostigmine. Reserved for severe agitation, hyperthermia or convulsions, and given slowly with atropine available, since it may cause bradycardia and convulsions
• Supportive care — benzodiazepines for agitation, active cooling for hyperthermia, catheterisation for retention, fluids, and a dark quiet environment
• Suspect datura in any traveller found confused and robbed with dilated pupils and a dry hot skin; the diagnosis is clinical and the history is usually absent because of the amnesia
• Do not mistake it for a psychiatric illness or for alcohol; the dry skin, dilated pupils, retention and tachycardia distinguish it, and treatment differs entirely
• Preserve the stomach contents and any seeds; botanical identification is straightforward and is the strongest evidence available
• Cool actively and early; hyperthermia with abolished sweating is what kills in the Indian climate, and antipyretics do not work because the mechanism is not a raised set point
• Warn that visual blurring persists for days; a patient discharged unable to read or to see clearly needs to know it will resolve
• Datura is the mirror of organophosphate poisoning, and the antidotes cross over exactly — atropine for one, physostigmine for the other