Acetaminophen Poisoning in Dogs

Is acetaminophen toxic to dogs?  

Acetaminophen (Tylenol), a common human drug used to control pain in fever, can be poisonous to dogs if inappropriate doses are given. Unfortunately, this is a relatively common poisoning. Dogs may get into the owner’s medication or owners may try to treat their dog’s pain at home. Acetaminophen is occasionally recommended by veterinarians for certain illnesses and should only be given under their direction. Young and small dogs have a higher risk of poisoning.

What are the signs of acetaminophen poisoning in dogs? 

Signs of poisoning from acetaminophen may develop within 4–12 hours of ingestion. Acetaminophen can cause liver damage, and it can decrease the red blood cells’ ability to carry oxygen (methemoglobinemia) by changing hemoglobin (an oxygen-carrying protein in red blood cells) to methemoglobin, a protein that cannot carry oxygen.

Dogs may become depressed or weak, with rapid breathing, a high heart rate, panting, abdominal pain, vomiting or drooling. Affected dogs may also stop eating. Mucous membranes, such as the gums or tissue around the globe of the eye, may develop a bluish color called cyanosis. These areas may also develop a chocolate brown color from methemoglobin that forms. Some dogs develop swelling in the face, paws, and forelimbs several hours after ingesting acetaminophen.

Liver damage may be delayed for up to one week. Signs of liver damage include dark urine, yellow discoloration of the eyes or skin, an enlarged abdomen, increased drinking and urination or discolored feces. If these signs are not recognized and treated, death may occur.

What is the treatment for a dog experiencing acetaminophen poisoning? 

Early decontamination and treatment decrease the risk of serious poisoning. If acetaminophen ingestion occurred within 15–20 minutes, the veterinarian may induce vomiting. Do not induce vomiting at home unless specifically directed by your veterinarian, as it may cause severe irritation of the stomach. Once vomiting is controlled, medical-grade activated charcoal may be administered to decrease absorption of acetaminophen by the gastrointestinal tract. Activated charcoal should only be given by a veterinarian. Improper administration of activated charcoal may lead to aspiration into the lungs and life-threatening changes in sodium levels.

Depending on the dose ingested, hospitalization may be needed. Fluids may be given under the skin or intravenously. An antidote is available for acetaminophen poisoning called N-acetylcysteine. Other medications, such as liver protectants, may also be given. If liver damage occurs or methemoglobin levels in the blood rise rapidly, more intensive treatment will be needed.

These changes increase the risk of long-term effects or even death. Patients that develop a low red blood cell count (anemia) or a decreased ability of the red blood cells to carry oxygen (methemoglobinemia) may require oxygen supplementation or a blood transfusion. Patients with liver damage often have an increased chance of bleeding. These patients may need vitamin K₁, plasma, or blood transfusions.

Once a dog is treated for acetaminophen poisoning, is any follow-up necessary?

Most dogs will need to continue medication for several weeks to support the liver. Liver enzymes are typically monitored to assess for liver damage after the dog is sent home. Depending on the dog’s condition, medication and monitoring may be needed for several days to weeks. Liver damage can affect long-term liver function in dogs who have recovered from acetaminophen poisoning.

Pet Poison Helpline, an animal 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 www.petpoisonhelpline.com.