Anticoagulant Rodenticide Poisoning in Dogs

By Renee Schmid, DVM, DABT, DABVT for Pet Poison Helpline; Ahna Brutlag, DVM, MS, DABT, DABVT; Rania Gollakner, BS, DVM, MPH

What are anticoagulant rodenticides?

Anticoagulant rodenticides are poisons used to kill mice, rats, and other rodents by preventing blood clotting. They are commonly found in hard bait blocks, soft baits (firm playdough consistency), and pellets, but may also be in powder, grain/meal, and liquid formulations.

There are several different active ingredients that may be used in anticoagulant rodenticides, including chlorophacinone, brodifacoum, bromadiolone, difenacoum, difethialone, diphacinone, and warfarin. The active ingredient and bait formulation depend on the product's intended place of use and federal regulations.

What is anticoagulant rodenticide poisoning?

Anticoagulant rodenticide poisoning occurs when a dog ingests a rodenticide containing an active ingredient that prevents blood clotting. This usually occurs when the poison is placed, without protective bait stations, in and around buildings, allowing access to the poison by dogs and other non-target animals.

"Anticoagulant rodenticide poisoning occurs when a dog ingests a rodenticide containing an active ingredient that prevents blood clotting."

When an animal is poisoned after it eats a rodent killed by the rodenticide, it is called secondary, or relay, poisoning. This can occur, but is rare, because a dog would need to eat many rodents that died from the poison.

How does poisoning occur?

Anticoagulant rodenticides cause excessive bleeding by interfering with vitamin K1 recycling in the body. Vitamin K1 is needed for the body to make certain clotting factors that enable blood to clot and help control bleeding. By preventing vitamin K1 recycling, anticoagulant rodenticides decrease vitamin K1 to levels that are too low to produce the needed clotting factors. Since the clotting factors cannot be produced, the body can no longer form clots needed to keep blood within its vessels, and uncontrolled bleeding may occur.

What are the clinical signs of anticoagulant rodenticide poisoning?

Initially, dogs do not show signs of anticoagulant poisoning. After ingesting this type of bait, it takes 1–2 days for vitamin K1 and clotting factors in the body to be used up. Next, it takes 3–7 days before signs of poisoning occur due to blood loss. Bleeding is not always obvious as it often occurs inside the abdomen, chest, lungs, joints, and gastrointestinal tract. In some cases, bleeding may be visible, such as from the mouth or nose.

Signs of internal bleeding may include weakness, depression, increased respiratory rate, difficulty breathing, coughing (which may produce blood), pale gums, lack of appetite, distended abdomen, vomiting, bloody or dark tarry stools, swelling or pain in the joints, and bruising. If bleeding happens within the brain or spinal cord, dogs may have neurologic signs. If bleeding is not recognized and treated, death may occur.

If you suspect your pet ingested an anticoagulant rodenticide, it is important to contact your veterinarian or Pet Poison Helpline, a 24/7 pet poison control center, at 1-800-213-6680 right away to help determine the risk of poisoning to your pet.

How is anticoagulant rodenticide poisoning diagnosed?

Most cases of poisoning are diagnosed in pets that have signs of bleeding and a known or suspected exposure to anticoagulant rodenticides. Blood work is often performed to assess blood clotting times, red blood cell count, and platelet counts. X-rays (radiographs) and ultrasound may be used to check for blood in the chest or abdomen.

"Treatment is often started without testing, if poisoning is suspected."

Measuring the levels of specific rodenticide active ingredients in the blood can be performed at a specialized veterinary diagnostic laboratory. Since the results may not be returned quickly, testing is uncommon. Treatment is often started without testing, if poisoning is suspected.

How is anticoagulant rodenticide poisoning treated?

Early decontamination and treatment decrease the risk of serious toxicity. If an anticoagulant rodenticide ingestion occurred within a few hours of treatment, the veterinarian may induce vomiting. Once vomiting is controlled, medical grade activated charcoal may be administered to decrease absorption of the anticoagulant rodenticide by the gastrointestinal tract. Activated charcoal should only be administered by a veterinarian. Otherwise, aspiration into the lungs and life-threatening changes in the blood sodium level may occur.

The antidote to anticoagulant rodenticide is vitamin K1, a prescription medication. This is given to increase vitamin K1 levels in the body and prevent bleeding.

Depending upon the time since ingestion and clinical signs present, hospitalized care may be needed. Fluids may be administered intravenously if needed. Dogs developing more serious signs may require intensive therapy, as they have an increased risk for death. Blood or plasma transfusions, oxygen therapy, or removal of blood from the chest and/or abdominal cavity may be needed, in addition to vitamin K1. Blood work to monitor blood clotting times, red blood cell counts, and platelet counts is commonly performed.

What care will my dog require after treatment?

When anticoagulant rodenticide poisoning occurs, vitamin K1 supplementation must be continued for several weeks. Approximately 48 hours after discontinuing vitamin K1, blood clotting times should be evaluated to ensure no further supplementation is needed. During the early stages of recovery at home, limited activity is recommended to prevent injuries that could cause bleeding. Once vitamin K1 supplementation can be discontinued, the dog can return to regular activities.

Pet Poison Helpline, a pet poison control center based out of Minneapolis, MN, is available 24/7 for pet owners and veterinary professionals that require assistance treating a potentially poisoned pet. The staff provides treatment advice for poisoning cases of all species, including dogs, cats, birds, small mammals, large animals, and exotic species. As the most cost-effective option for animal poison control care, Pet Poison Helpline’s per-incident fee includes follow-up consultations for the duration of the poison case. Pet Poison Helpline is available in North America by calling 800-213-6680. Additional information can be found online at 

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