ACMT Toxicology Visual Pearls: Awake Seizures?

Sep 14, 20
ACMT Toxicology Visual Pearls: Awake Seizures?

Which of the following rodenticides, often used to kill the rodent pictured, causes seizure-like activity without altered mental status or a postictal period?

  1. Barium
  2. Brodifacoum
  3. Carbamate
  4. Strychnine
  5. Zinc phosphide

Answer: 4 – Strychnine in rodenticide, often used in “gopher bait.”

What is strychnine and how does it cause toxicity [1-5]? 

  • Strychnine is an odorless, bitter-tasting alkaloid derived from the seeds of the Strychnos nux-vomica and related plants.
  • Strychnine is still commercially available as a rodenticide in the US, but use is banned elsewhere.
  • Strychnine is a competitive antagonist of the inhibitory neurotransmitter glycine with predominant activity in the spinal cord.
  • Exposed patients develop painful involuntary muscle contractions which can be mistaken for seizure activity.
  • Mental status remains intact

How are patients exposed [5,6]? 

  • Accidental or intentional ingestion of rodenticides containing strychnine
  • Use of the Chinese or Cambodian herbal medications Ma Qian Zi and slang nut
  • Historically, use of cocaine or heroin adulterated with strychnine
  • Inhalation or dermal exposure also results in toxicity

How does strychnine toxicity present [5-9]?

  • Onset is rapid after oral exposure but may be delayed up to 12 hours following dermal exposure
  • Episodic, painful, involuntary muscle spasms lasting up to 2 minutes at a time that recur over a 12-24 hour period
  • Flexion of upper extremities and extension of lower extremities are commonly reported
  • Spasms can be triggered by mild stimuli such as turning on room lights
  • Patients are reported to be hyperexcitable or agitated
  • Nystagmus, clonus, risus sardonicus, opisthotonos, and trismus are also reported
  • Prolonged muscle contraction can result in rhabdomyolysis and acute kidney injury, metabolic acidosis, hypocalcemia, hyperkalemia, and hyperthermia.
  • Compartment syndrome has been reported
  • Hypoxia may occur due to hypoventilation
  • True seizures and death due to respiratory and/or cardiac arrest have been reported

How do you diagnose and treat strychnine toxicity [2,5,8-10]?

  • History and physical exam
  • Decontaminate skin for dermal exposure
  • Acute tetanus should be part of the differential diagnosis with other considerations including status epilepticus, dystonic reaction, and NMS
  • Activated charcoal may be considered if less than 1-2 hours post-ingestion and airway is protected
  • Diagnostic testing should include a chemistry panel, renal function, and CPK
  • Limit noise and physical stimulation by placing the patient in a quiet dark room
  • Strychnine levels may be obtained from blood or urine.
  • Supportive care includes the administration of IV fluids and the correction of electrolyte abnormalities.
  • Treatment with benzodiazepines will increase inhibitory neurotransmission and promote muscle relaxation.
  • If intubation is required, avoid nondepolarizing neuromuscular blockers and sedate generously.
  • In extreme cases, paralytics may be required.
  • Monitor for hyperthermia and treat if necessary

Take-Home Bedside Pearls:

  • Consider strychnine toxicity in patients with apparent awake “seizures.”
  • Aggressive use of benzodiazepines is the mainstay of therapy.
  • Keep the patient in a low stimulation setting.
  • Intubation with nondepolarizing paralytics and active cooling may be needed.
  • Evaluate for rhabdomyolysis, acute kidney injury, and electrolyte abnormalities.

Want more ACMT Visual Pearls? Check out the ALiEM Archives!

This post has been peer-reviewed on behalf of ACMT by Dr Bryan Judge, Dr Louise Kao, and Dr David Wood.

References

  1. Greene R, Meatherall R. Dermal exposure to strychnine. J Anal Toxicol. 2001;25(5):344-347. doi:10.1093/jat/25.5.344. PMID: 11499889
  2. Mackerer CR, Kochman RL, Shen TF, Hershenson FM. The binding of strychnine and strychnine analogs to synaptic membranes of rat brainstem and spinal cord. J Pharmacol Exp Ther. 1977;201(2):326-331. PMID: 16120
  3. Curtis DR, Duggan AW, Johnston GA. The specificity of strychnine as a glycine antagonist in the mammalian spinal cord. Exp Brain Res. 1971;12(5):547-565. doi:10.1007/BF00234248. PMID: 5093729
  4. Teitelbaum DT, Ott JE. Acute strychnine intoxication. Clin Toxicol. 1970;3(2):267-273. doi:10.3109/15563657008990475. PMID: 5527848
  5. Chan Y. Strychnine. In: Hoffman RS, Howland M, Lewin NA, Nelson LS, Goldfrank LR. eds. Goldfrank’s Toxicological Emergencies, 11e New York, NY: McGraw-Hill; 2019
  6. Boyd RE, Brennan PT, Deng JF, Rochester DF, Spyker DA. Strychnine poisoning. Recovery from profound lactic acidosis, hyperthermia, and rhabdomyolysis. Am J Med. 1983;74(3):507-512. doi:10.1016/0002-9343(83)90999-3. PMID: 6829597
  7. Hardin JA, Griggs RC. Diazepam treatment in a case of strychnine poisoning. Lancet. 1971;2(7720):372-373. doi:10.1016/s0140-6736(71)90085-7. PMID: 4105067
  8. Jackson G, Ng SH, Diggle GE, Bourke IG. Strychnine poisoning treated successfully with diazepam. Br Med J. 1971;3(5773):519-520. doi:10.1136/bmj.3.5773.519. PMID: 341168
  9. Maron BJ, Krupp JR, Tune B. Strychnine poisoning successfully treated with diazepam. J Pediatr. 1971;78(4):697-699. doi:10.1016/s0022-3476(71)80480-8. PMID: 5547830

Author information

Kregg Laundon, MD

Kregg Laundon, MD

Emergency Medicine Physician
Memorial Hospital
Savannah, GA

The post ACMT Toxicology Visual Pearls: Awake Seizures? appeared first on ALiEM.

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