Datura Poisoning: The Anticholinergic Toxidrome

Datura stramonium and Datura metel grow as weeds across India, and every part of the plant is poisonous. Forensic medicine cares about Datura because it is a classical stupefying agent — historically mixed into food or drink by highway robbers, which is why it is still known as the “road poison”.

At a glance

The toxidrome

The old rhyme still earns marks because it is genuinely complete:

Add tachycardia, absent bowel sounds, and characteristic picking or plucking movements at the bedclothes with mumbling incoherent speech — a description that has been recognisable for two centuries.

The crucial distinction

Anticholinergic and sympathomimetic poisoning both produce an agitated, tachycardic, hyperthermic patient with big pupils. The skin separates them. Anticholinergic poisoning gives hot, dry, flushed skin with retention and absent bowel sounds. Sympathomimetic poisoning gives a sweating patient with normal or increased bowel sounds. Getting this distinction right in a viva is worth more than reciting the whole mnemonic.

Management

1. Supportive care is the mainstay. Airway, monitoring, intravenous fluids.
2. Benzodiazepines for agitation and to control the hyperthermia that agitation drives. Physical restraint alone worsens hyperthermia and rhabdomyolysis.
3. Active cooling for significant hyperthermia.
4. Activated charcoal may be useful; anticholinergic slowing of gut transit means the window is longer than usual.
5. Catheterise for retention.
6. Physostigmine is reserved for severe central anticholinergic delirium unresponsive to benzodiazepines, and only under monitoring with atropine available. It is contraindicated where tricyclic antidepressant co-ingestion is possible, because it can precipitate asystole and seizures.

Forensic points

Datura is used to stupefy victims before robbery, and less commonly for homicide or suicide. Seeds may be recovered from gastric contents at autopsy and are identifiable on examination. Preserve stomach contents and viscera in saturated saline. Because the effects include amnesia, victims often cannot give a reliable account of what happened — a point with real medicolegal weight.

Last-minute checklist

• Atropine, hyoscyamine, scopolamine; muscarinic blockade.
• Dry skin distinguishes it from a sympathomimetic.
• Picking movements and mumbling delirium are classical.
• Benzodiazepines and cooling first; physostigmine rarely, never with possible TCA.
• Saturated saline for viscera.

Frequently asked questions

How do you tell anticholinergic from sympathomimetic poisoning at the bedside?

Feel the skin. Anticholinergic patients are hot, dry and flushed with urinary retention and silent bowels; sympathomimetic patients sweat and have active bowel sounds.

Why is physostigmine dangerous if tricyclics may have been taken?

Tricyclics block sodium channels and slow cardiac conduction. Adding a cholinesterase inhibitor can precipitate bradyarrhythmia, asystole and seizures, so it is avoided when the ingestion is uncertain.

Why is Datura called the road poison?

Because it was classically administered in food or drink to travellers in order to stupefy them for robbery, and it produces amnesia that makes the victim an unreliable witness afterwards.

References

• Reddy KSN, Murty OP. The Essentials of Forensic Medicine and Toxicology.
• Parikh CK. Textbook of Medical Jurisprudence, Forensic Medicine and Toxicology.
• Goodman & Gilman’s The Pharmacological Basis of Therapeutics — muscarinic antagonists.