UMEM Educational Pearls

Category: Toxicology

Title: Strychnine Poisoning: Differential Diagnosis

Keywords: strychnine, seizure, tetanus (PubMed Search)

Posted: 5/7/2013 by Bryan Hayes, PharmD (Emailed: 5/9/2013) (Updated: 5/9/2013)
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Strychnine poisoning is still occasionally found in rat poisons and in adulterated street drugs and herbal products. The typical symptoms are involuntary, generalized muscular contractions resulting in neck, back, and limb pain. The contractions are easily triggered by trivial stimuli (such as turning on a light) and each episode usually lasts for 30 seconds to 2 minutes, for 12 to 24 hours. Classic signs include opisthotonus, facial trismus, and risus sardonicus.

Differential diagnosis includes:

  • Tetanus: However, the onset of symptoms is more gradual and the duration much longer than in the case of strychnine poisoning.
  • Generalized seizures: However, strychnine poisoning presents with a normal sensorium during the period of diffuse convulsions.
  • Dystonic reaction: However, dystonic reactions are usually static, whereas strychnine poisoning results in dynamic muscular activity. 
  • Serotonin syndrome
  • Malignant hyperthermia
  • Neuroleptic malignant syndrome
  • Stimulant use


Chan Y. Chapter 112. Strychnine. In: Chan Y, ed. Goldfrank's Toxicologic Emergencies. 9th ed. New York: McGraw-Hill; 2011. Accessed May 7, 2013.

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