Datura and Plant Poisonings
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Direct answer
Datura stramonium poisoning produces an anticholinergic toxidrome, with dilated pupils, dry flushed skin, urinary retention and delirium, because its tropane alkaloids block muscarinic receptors. Oleander contains cardiac glycosides and causes digoxin-like arrhythmias, while castor seeds contain ricin and abrus seeds contain abrin, both toxalbumins that injure the gut and several organs. Management is largely supportive, with specific antidotes used only for particular plant toxins.
What you must remember
- Anticholinergic toxidrome: Dilated pupils, dry skin, hyperthermia, tachycardia, urinary retention, reduced bowel sounds and delirium with visual hallucinations.
- Datura alkaloids: Atropine, hyoscine and hyoscyamine are tropane alkaloids that cross the blood brain barrier and cause central effects.
- Physostigmine: Reserved for severe, life-threatening anticholinergic delirium, and avoided with tricyclic co-ingestion or conduction abnormality.
- Oleander: Cardenolides cause bradyarrhythmias, atrioventricular block and hyperkalaemia; digoxin-specific antibody fragments are used in severe cases.
- Castor: Ricin from chewed Ricinus communis seeds inhibits protein synthesis, causing vomiting, gastrointestinal bleeding and multi-organ failure, while whole seeds may pass unabsorbed.
- Abrus precatorius: Abrin, a toxalbumin similar to ricin, causes gastrointestinal bleeding and renal injury after chewed seeds, with supportive care as the mainstay.
Two plant ingestions with different treatment paths
Two plant ingestions call for two different treatment paths, one for anticholinergic toxicity and one for cardiac glycoside toxicity.
- Recognise the datura picture: A 16-year-old is brought in after eating datura fruit and seeds, agitated and hallucinating, with a temperature of 39.2 degrees, dilated pupils, dry skin and urinary retention. The picture is anticholinergic rather than cholinergic.
- Prioritise the datura care: The priorities are cooling, benzodiazepines for agitation, catheterisation for retention, and monitoring of heart rate and rhythm.
- Decide on physostigmine: Physostigmine is reserved for delirium that threatens safety, and it is avoided if the ECG shows prolonged conduction or tricyclic co-ingestion is possible.
- Recognise the oleander picture: A farmer's child who has eaten oleander presents with vomiting, a pulse of 38 and a potassium of 6.1 mmol/L. The cardiac glycoside mechanism applies, so the approach mirrors digoxin toxicity.
- Treat the oleander toxicity: Atropine is given for bradycardia, electrolytes are corrected and antibody fragments are used for severe arrhythmia.
- Support after castor: A third ingestion of castor seeds presents with bloody vomiting and hypovolaemia. Ricin has no antidote, so fluids, blood products where needed and organ monitoring are the mainstay.
Where the exam tries to catch you
Plant poisoning questions test the same few confusions.
- Trap: Confusing datura with a cholinergic crisis. Correct: Datura causes a dry, hot, delirious patient rather than a sweating, bradycardic one, because its atropine-like alkaloids are responsible.
- Trap: Dismissing oleander as a harmless garden plant. Correct: Common and yellow oleander both contain cardiac glycosides, so the hyperkalaemia and conduction block must not be missed.
- Trap: Looking for a specific antidote for ricin or abrin. Correct: Both are toxalbumins that inhibit protein synthesis with no specific antidote, so a supportive answer is expected.
Frequently asked questions
What is the classic mnemonic for anticholinergic toxicity features?
The classic teaching phrase is dry as a bone, red as a beet, hot as a hare, blind as a bat and mad as a hatter, which covers dry skin, flushing, hyperthermia, mydriasis and delirium. Datura poisoning typically produces every one of these features, which makes it a standard anticholinergic toxidrome example.
Why does oleander poisoning mimic digoxin toxicity?
Oleander contains cardenolides, which are cardiac glycosides that inhibit the sodium potassium ATPase in the same way as digoxin. Bradyarrhythmias, atrioventricular block and hyperkalaemia follow, and digoxin-specific antibody fragments are used in severe cases.
Which plant toxalbumin causes gastrointestinal bleeding and has no specific antidote?
Ricin from castor seeds is a toxalbumin that inhibits protein synthesis, causing vomiting, gastrointestinal bleeding and multi-organ failure after the seeds are chewed. No specific antidote exists, so treatment is supportive with fluid, electrolyte and blood product management.
When is physostigmine used in datura poisoning?
Physostigmine is reserved for severe anticholinergic delirium or agitation that threatens safety and does not respond to supportive care such as benzodiazepines. It is avoided when tricyclic antidepressants are co-ingested or conduction abnormalities are present, because it may precipitate seizures or asystole.