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.