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ACMT Toxicology Visual Pearls: Toxic “Weed”

Posted by Leslie R. Dye, MD, FACMT on

A patient presents to the ED after eating seeds from a plant to “get high.” What toxidrome is expected after ingesting these seeds?

  1. Antimuscarinic
  2. Cholinergic
  3. Nicotinic
  4. Opioid
  5. Sympathomimetic

Reveal the Answer

Answer: 1 – Antimuscarinic

Antimuscarinic Toxidrome

This plant is Datura Stramonium, and some common names are jimsonweed, stink weed, locoweed, thornapple, and devil’s trumpet. The plant is a member of the nightshade family. It is an annual, grows worldwide in temperate regions, flowers during summer, and is considered a weed. The leaves, when crushed, produce a distinctive odor, which has been compared to peanut butter. The capsule is spiked, divided into 4 chambers, and contains small, black seeds.1 These seeds can be intentionally ingested, smoked, or brewed into a tea to produce hallucinations.

Toxicity occurs from blocking the action of acetylcholine by competitive antagonism at muscarinic receptor sites, resulting in an antimuscarinic toxidrome.2

Common signs include:

  • Dry flushed skin
  • Mydriasis
  • Hyperthermia
  • Dry mucous membranes
  • Tachycardia
  • Hypertension
  • Bladder distention
  • Decreased bowel sounds
  • Mental status changes (e.g., confusion, agitation, hallucinations)

Other agents that can produce the antimuscarinic toxidrome include3 :

  • Antihistamines
  • Antipsychotics
  • Antispasmodics
  • Cyclic antidepressants
  • OTC sleep aids
  • (Some) muscle relaxants
  • Mydriatics

Antimuscarinic Toxicity: Bedside Pearls

Differentiation from Sympathomimetic Toxidrome

The sympathomimetic and antimuscarinic toxidromes can present similarly, and are sometimes mistaken for each other by clinicians. While a decrease in bowel sounds occurs with antimuscarinic toxidrome, this finding can be difficult to discern.

The best way to differentiate antimuscarinic from sympathomimetic toxidromes is by examining the skin:

Toxidrome Skin Exam Findings
Antimuscarinic Dry (axillae in particular)
Sympathomimetic Diaphoresis

Diagnostic Trial of Physostigmine

Administration of the antidote, physostigmine, is a rapid method to confirm the diagnosis of antimuscarinic toxidrome. Physostigmine is a short-acting, reversible inhibitor of acetylcholinesterase. The antidote controls agitation in up to 87% and reverses delirium in 96% of patients with pure antimuscarinic toxicity.4 Its effects are noted within minutes and last approximately 1 hour. Temporary reversal of delirium may be diagnostic and thereby preclude the need for further testing, including brain imaging and lumbar puncture.

The initial dose is 0.5-1 mg in adults and 0.01-0.02 mg/kg (maximum 0.5 mg) in children, and should be administered IV over 5 minutes.4

Physostigmine should not be used in the presence of:

  • Asthma
  • Gangrene
  • Cardiovascular disease
  • Mechanical obstruction of the intestine or GU tract
  • Any vagotonic state

Adverse effects include cholinergic symptoms:

  • Diarrhea and vomiting
  • Bronchorrhea
  • Seizures

Physostigmine may prolong the activity of depolarizing neuromuscular agents such as succinylcholine. Ventricular arrhythmias and asystole have been reported when administered to patients with sodium channel blockade after cyclic antidepressant overdose.5,6

This post was peer-reviewed by Dr. R Brent Furbee, Dr. Bryan Judge, and Dr. Louise Kao.

The American College of Medical Toxicology (ACMT) hosts this Toxicology Visual Pearls series.

References

1.
Nelson L. Handbook of Poisonous and Injurious Plants. 2nd ed. New York, NY: Springer; 2007.
2.
Brown J. Goodman and Gilman’s the Pharmacologic Basis of Therapeutics. 14447th ed. New York, NY: McGraw-Hill; 1996.
3.
Shannon M W, Borron S W, J. Burns (MD.) M, Haddad L M, Winchester J F. Haddad and Winchester’s Clinical Management of Poisoning and Drug Overdose. 4th ed. Oxford, England: W B Saunders Company; 2007.
4.
Dawson A, Buckley N. Pharmacological management of anticholinergic delirium – theory, evidence and practice. Br J Clin Pharmacol. 2016;81(3):516-524. [PubMed]
5.
Schneir A, Offerman S, Ly B, et al. Complications of diagnostic physostigmine administration to emergency department patients. Ann Emerg Med. 2003;42(1):14-19. [PubMed]
6.
Akon Pharmaceuticals, Physostigmine Salicylate Injection. Akon. http://www.akorn.com/documents/catalog/package_inserts/17478-510-02.pdf. Published June 2016. Accessed 2017.

Author information

Leslie R. Dye, MD, FACMT

Editor-in-Chief, Point of Care Content, Elsevier
Immediate Past President, ACMT

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