Warfarin rat poison is a first-generation anticoagulant rodenticide used to control pest populations like rats and mice. It is formulated into baits for consumption by rodents. Its purpose is to induce internal bleeding, which is fatal to the affected pest. The compound first appeared commercially as a rat poison in 1948.
The Anticoagulant Mechanism
Warfarin interferes with the body’s natural blood clotting process. It inhibits the enzyme vitamin K epoxide reductase, which recycles vitamin K1 in the liver. Without enough active vitamin K1, the liver cannot synthesize plasma clotting factors, including factors II, VII, IX, and X. This disruption prevents the normal formation of fibrin, a protein essential for blood clots.
The depletion of these clotting factors leads to a coagulopathy, where blood loses its ability to clot. This results in uncontrolled internal bleeding, which is fatal to the affected rodent. The same compound, warfarin sodium, is prescribed as a blood-thinning medication for humans to prevent blood clots. Its use in human medicine began in 1954, after its initial use as a rodenticide.
Symptoms of Accidental Exposure
Accidental exposure to warfarin rodenticides poses a risk to non-target animals, especially pets like dogs and cats. Pets can be poisoned by directly ingesting the bait or by secondary poisoning (consuming a poisoned rodent). Signs of poisoning are often delayed, appearing 3 to 7 days after ingestion, making diagnosis challenging without a known history of exposure. This delay happens because existing clotting factors must be depleted before bleeding becomes apparent.
Clinical signs of warfarin poisoning in animals result from internal bleeding. Affected pets may exhibit lethargy, weakness, and pale gums due to blood loss. Respiratory distress, characterized by coughing or difficulty breathing, can indicate bleeding into the lungs or chest cavity. Unexplained bruising or petechiae, which are small pinpoint hemorrhages, may be visible on the skin or mucous membranes. Other symptoms include nosebleeds, blood in vomit (hematemesis), bloody diarrhea (melena or hematochezia), or blood in the urine (hematuria).
Veterinary and Medical Treatment
Immediate veterinary intervention is essential if accidental warfarin poisoning is suspected. The specific antidote for anticoagulant rodenticide poisoning is vitamin K1. This treatment restores the body’s ability to produce functional clotting factors, counteracting the poison’s effects. Vitamin K1 therapy is administered orally and often continues for several weeks, commonly two to four weeks, to ensure complete recovery and prevent recurrence of bleeding.
In severe cases of poisoning, where blood loss has occurred, hospitalization may be necessary. These situations might require supportive care like intravenous fluids and blood transfusions to stabilize the patient and replenish lost blood. Bringing the poison’s original packaging to the veterinarian is recommended, as it provides important information regarding the active ingredient and concentration, aiding in tailoring the most effective treatment plan.