Acetaminophen Poisoning in Cats

Is acetaminophen toxic to cats? 

Acetaminophen (Tylenol), a common human drug used to control pain and fever, is poisonous to cats. Unfortunately, this is a relatively common poisoning due to owners trying to treat their cat’s pain at home. Less commonly, cats may get into the owner’s medication.

Since cats are not able to efficiently metabolize acetaminophen, they are more vulnerable to toxicity. Cats develop toxicity at much lower doses than dogs.

What are the signs of acetaminophen poisoning in cats? 

Signs of poisoning from acetaminophen may develop within 1–4 hours of ingestion. Acetaminophen can cause a decrease in 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. Red blood cell changes can occur within 4–12 hours. Liver damage may also occur.

Cats may become depressed or weak, with rapid breathing, a high heart rate, panting, abdominal pain, vomiting or drooling. Affected cats 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 cats 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 cat experiencing acetaminophen poisoning? 

Early decontamination and treatment decrease the risk of serious poisoning. If acetaminophen ingestion occurred within 15–20 minutes, a veterinarian may induce vomiting. Inducing vomiting should never be attempted at home 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 therapy 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. Cats with liver damage often develop an increased chance of bleeding. These cats may need vitamin K₁, plasma, or blood transfusions.

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

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

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 www.petpoisonhelpline.com.