ACMT Toxicology Visual Pearls: Awake Seizures?

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.