Strychnine poisoning in dogs

Strychnine is a bitter alkaloid substance extracted from the seeds of a tree called Strychnos nux vomica. Strychnine is used to control populations of ground squirrels, meadow and deer mice, prairie dogs, rats, porcupines, chipmunks, rabbits and pigeons. Baits containing strychnine are often died red, green or blue and are combined with grain. Availability of over-the-counter versions of the poison varies across the country. Some formulations are available only through licensed pest control operators.

Strychnine is quickly absorbed from the stomach, causing rapid onset of clinical signs. Strychnine acts on the animal’s nervous system to cause profound stimulation, with severe muscle spasms and seizures. Strychnine is highly toxic to all animals, including humans.

Clinical signs are similar among all animals and can develop as quickly as 10 minutes after ingestion. Initially, animals may appear anxious or nervous, have a rapid rate of breathing, and have excess drooling or salivation. Vomiting is uncommon. The signs usually progress to generalized muscle stiffness, tremors and seizures. The dog’s mouth may be clamped shut and the neck arched back. Death occurs from impaired breathing secondary to muscle stiffness. Depending upon the dose ingested, death can occur within minutes to hours.

Diagnosis is based on a history of exposure, consistent clinical signs and finding strychnine in bait or in stomach contents. There are no specific blood tests that confirm strychnine ingestion. In some cases, strychnine may be found in urine.

Because strychnine can cause a very rapid onset of clinical signs, the opportunity to induce vomiting and remove the poison from the stomach is often lost. Your veterinarian may administer activated charcoal to try and prevent absorption of the poison. Most affected animals must be hospitalized for emergency treatment. The muscle stiffness, tremors and seizures can be managed with anticonvulsants and muscle relaxants. Intravenous fluids are always necessary. Respiratory support with oxygen is also necessary.

Dr. Karsten Fostvedt is a veterinarian at St. Francis Pet Clinic in Ketchum.

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