Is Strychnine safe for dogs and cats?

Strychnine is an alkaloid derived from the seeds of Strychnos nux-vomica (strychnine tree), used historically as a rodenticide and mole/gopher control agent. Mechanism: potent competitive antagonist of glycine at glycine receptors in the spinal cord and brainstem → loss of inhibitory neurotransmission → uncontrolled motor neuron firing → generalized tetanic convulsions. Minimum lethal dose in dogs: approximately 0.75–1.0 mg/kg — extremely low. Even small quantities of strychnine bait can be fatal to a dog. Onset: 15–60 minutes after ingestion. Clinical signs: extreme hypersensitivity to stimuli (touch, sound, light), violent tetanic extensor rigidity, opisthotonus (arched back, neck extension), muscle fasiculations progressing to severe tetanic seizures, respiratory failure from sustained thoracic muscle rigidity, hyperthermia from muscular exertion. Death results from respiratory failure and hypoxia during sustained seizures. No antidote. Treatment must begin immediately: if very recent ingestion (within 30 minutes and before symptoms), apomorphine-induced emesis in a quiet, dark environment; anesthesia induction (gas anesthesia) to halt tetanic activity; mechanical ventilation; cooling for hyperthermia; sedation/anesthesia maintained until strychnine is eliminated (urinary alkalinization accelerates excretion). Strychnine has been largely banned for commercial use in the US (EPA canceled most registrations), but illicit formulations persist, and registered uses remain for mole control below ground. Strychnine poisoning is also used in deliberate pet killings.

Cats are equally sensitive to strychnine as dogs, with a similar minimum lethal dose (~0.5–1.0 mg/kg). Cats may encounter strychnine through deliberate baiting or through consuming poisoned rodents (secondary poisoning). The clinical syndrome is identical: violent tetanic convulsions triggered by any sensory stimulation, opisthotonus, hyperthermia, and respiratory failure. Management requires the same approach as in dogs — induction of anesthesia to prevent sustained tetanic contractions, mechanical ventilation, and intensive supportive care. In cats, the extreme sensitivity to sensory stimuli makes transport to a veterinary facility hazardous without pre-sedation; owners should minimize sensory stimulation (dark, quiet transport) and seek emergency veterinary care immediately. Prognosis is guarded even with treatment; rapid onset and severity of convulsions make successful management dependent on immediacy of intervention.