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Rodenticide (Warfarin) Poisoning in Dogs

By Rania Gollakner, BS DVM

Emergency Situations, Medical Conditions, Pet Services

What is warfarin rodenticide?poison

Warfarin rodenticide is an over-the-counter, first generation, coumarin anticoagulant rodenticide used to kill mice, rats, and other pests. Coumarin anticoagulants are a group of natural and synthetic compounds that prevent the blood from clotting.


What is warfarin rodenticide poisoning?

Warfarin rodenticide poisoning (brand names: Bar Bait, Contrax-W, Co-Rax, Coumafene, Cov-R-Tox, Denkarin, Dethmor, Dicusat E, Final, Kypfarin, Luxarin, Prolin, Ramorin, Rat and Mouse Killer, Ratoxin, RAX, Rodex, Tox-Hid, Warfotox, Zoocoumarin) occurs when a dog ingests the rodenticide accidentally. This usually occurs when the poison is placed in and around buildings without protective bait stations, allowing access to the poison by dogs and other unintended animals.


How does poisoning occur?

Warfarin rodenticide prevents vitamin K1 from working properly in the body. Vitamin K is required for the activation of clotting factors; these clotting factors are required to help clot formation and to stop active bleeding. Therefore, when warfarin inactivates vitamin K1, the body can no longer form clots and bleeding will occur uncontrollably (hemorrhage).


What are the clinical signs of warfarin rodenticide poisoning?

Clinical signs of poisoning are hemorrhage (bleeding) which usually occurs about 2-3 days after consumption. The first clinical signs are often associated with the respiratory system, such as coughing (sometimes coughing up blood), difficulty breathing, rapid breathing, or exercise intolerance.

"Without treatment, death will eventually occur."

Other clinical signs include joint swellings, swellings under the skin, or bleeding from the nose, mouth, vagina, or rectum. Gastrointestinal signs such as bloody diarrhea, black stools, and vomiting blood can also occur. Other signs include poor pulses, pale gums, lameness, lethargy, depression, muffled heart sounds, and collapse. Without treatment, death will eventually occur.


How is warfarin rodenticide poisoning diagnosed?

Warfarin rodenticide poisoning is diagnosed by a combination of a history of warfarin exposure or ingestion, clinical signs, and diagnostic tests, including clotting time tests.

Blood work is useful for identifying anemia, low platelet counts, and prolonged clotting times. Radiographs (X-rays) and ultrasound can identify fluid (blood) in the chest or abdomen. Special analysis of the blood or liver can confirm exposure to specific products such as warfarin, which is helpful in deciding the vitamin K1 therapy duration.


How is warfarin rodenticide poisoning treated?

If the rodenticide was recently ingested, your veterinarian will induce vomiting followed by the administration of activated charcoal to prevent further absorption of the rodenticide. Once clinical signs have developed, inducing vomiting is no longer useful, and medical management is the treatment of choice.

"High doses of vitamin K1 must be administered for several weeks after exposure."

High doses of vitamin K1 must be administered for several weeks after exposure in order to replace the damaged vitamin K1 in the body. In addition to vitamin K1 supplementation, supportive care may be necessary depending on the clinical signs. This includes intravenous fluid therapy and blood transfusions to treat life-threatening hemorrhage, and the removal of blood from around the heart or lungs to improve breathing and circulation if necessary.


What care will my dog require after treatment?

Vitamin K1 supplementation must continue for up to 6 weeks after exposure to an anticoagulant rodenticide. Approximately 36-48 hours after discontinuing the vitamin, the clotting time tests must be repeated; supplementation is no longer needed if the result is normal. During the early stages of recovery at home, the patient should be confined to prevent injuries that could cause bleeding. A high-quality protein diet should also be fed for several months after the toxic exposure. Once vitamin K1 supplementation is discontinued, the patient can return to regular activities.

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