Strychnine is an alkaloid pesticide toxin used commercially for eradication of vermin. It is commonly extracted from the Strychnine tree (Strychnos nux-vomica).
Although the use of strychnine is highly regulated by government authorities, in developing countries it is regularly used as an intentional poisoning for urban canine population control.
Strychnine at dose between 0.5 - 1 mg/kg is a neurotoxin which acts as an antagonist of glycine and acetylcholine receptors on neuromuscular junctions in skeletal muscle fibres, causing uncontrolled fasciculation.
Accidental ingestion by dogs results in muscular convulsions and respiratory paralysis leading to acute death.
There are no characteristic necropsy lesions but sometimes, due to prolonged convulsions before death, agonal hemorrhages of heart and lungs and cyanotic congestion from anoxia may be seen. Animals dying from strychnine poisoning have rapid rigor mortis.
A presumptive diagnosis can be made on exposure to this chemical and clinical symptoms. A definitive diagnosis requires screening for alkaloids by liquid chromatography at reference laboratories.
A differential diagnosis would include mycotoxicosis and snail-bait toxicity.
Treatment usually involves aggressive intravenous fluid therapy, establishment of general anesthesia with thiopentone, use of muscle relaxants such as methocarbamol or diazepam and oxygen assistance. The prognosis is guarded in most cases, and recovery is often prolonged.
Acute renal injury is a common complication and acidification of urine with ammonium chloride may be useful for ion-trapping and urinary excretion of the alkaloid.
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- Merck Veterinary Manual
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