Acetaminophen (Tylenol) Poisoning Alert for Dogs and Cats

Acetaminophen (Tylenol®, Paracetamol, APAP, N-acetyl-paraminophenol) is a medication used for pain relief and fever reduction in people. It is a popular over-the-counter oral medication and is also available by prescription.

Acetaminophen may be the only ingredient in a medication or be part of a combination product containing other medications. These medications may include aspirin, opioids, antihistamines, decongestants, and caffeine. Typical uses in people include the treatment of fever, pain, colds, flu, and menstrual discomfort.

Acetaminophen is available in many forms, including tablets, capsules, gel caps, melt away tablets, rectal suppositories, and liquids. Acetaminophen is often found in homes with pets. Poisoning may happen when pets get into the owner’s medications. In some cases, owners may administer acetaminophen at unsafe doses to treat their pet’s pain. Low doses of acetaminophen may be recommended in dogs for certain indications and should only be given under the direction of a veterinarian.

Why is acetaminophen (Tylenol) poisonous for dogs and cats?

Acetaminophen is generally safe for humans at the recommended dose. The metabolism (mechanism for breaking down and removing drugs from the body) of acetaminophen is different in dogs and cats than in humans. This means that relatively small doses, even a small piece of a pill, may be poisonous for dogs or cats.

"Cats develop toxicity at much lower doses than dogs."

Cats are especially sensitive to acetaminophen. Cats have fewer cellular pathways for certain types of drug metabolism, including acetaminophen. Since cats are not able to efficiently metabolize acetaminophen, they are more vulnerable to poisoning. Cats develop toxicity at much lower doses than dogs.

What should I do if my dog or cat eats acetaminophen?

If the exposure has just occurred and your pet is not yet showing any signs of illness, contact your veterinarian or Pet Poison Helpline, a 24/7 poison control center for animals, at 800-213-6680. Early assessment and treatment increase the chance for a safe and successful outcome.

If your dog or cat is showing any signs of distress, immediately transport your pet to your veterinarian or closest veterinary emergency clinic. Be sure to take the pill bottle and remaining pills with you. It is important to provide as much information as possible about the type of medication, amount ingested, timing of ingestion, and symptoms. It may be helpful to take an old blanket or towel in case your pet becomes nauseated and vomits during the car ride. 

"If your dog or cat is showing any signs of distress, immediately transport your pet to your veterinarian or closest veterinary emergency clinic."

If vomiting occurs, check for any evidence of medication, and note the amount present before discarding the vomit. If you are not able to do this, save the vomit so that the veterinary staff can examine it for you.

Try to stay calm and provide as much information as possible when requested by your veterinarian or Pet Poison Helpline. Provide information for all pets with access to the mediation. This information is critical to judge the risk of poisoning and to provide the best possible recommendations for your dog or cat.

Information that may be requested includes:

• Age, weight, and breed of the pet.
• Time of ingestion.
• The amount of medication ingested (if the number of pills that was originally present in the bottle is known, count the remaining pills to determine how many were ingested).
• The strength of the medication (how many milligrams per pill or per mL).
• Any other ingredients present in the pills (e.g., antihistamine, caffeine).
• The pet’s medical history, including what other medication they are taking, if any.
• Any current symptoms.

What are the signs of acetaminophen (Tylenol) poisoning in dogs or cats?

Pets may show no signs initially. 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. Cats are more likely to develop early red blood cell changes, while dogs are more likely to develop liver damage. Depending on the dose, both red blood cell changes and liver damage may occur in either species.

"Depending on the dose, both red blood cell changes and liver damage may occur in either species."

Red blood cell changes can occur within 1–12 hours. Pets may become weak and depressed. They also may stop eating and develop rapid breathing, a high heart rate, panting, abdominal pain, vomiting, or drooling. Mucous membranes, including 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. Some pets develop swelling in the face, paws, and forelimbs several hours after ingesting acetaminophen.

Liver damage may be delayed for several days. In addition to the signs above, dark urine, yellow discoloration of the eyes or skin, an enlarged abdomen, increased drinking and urination or discolored feces may be seen. If these signs are not recognized and treated, death may occur.

Dry eye (keratoconjunctivitis) can also be caused by acetaminophen poisoning. Squinting, discharge from the eyes, pawing at the face and eye pain are signs of this condition. This is uncommon and most frequently seen in small breed dogs. If the ingested acetaminophen was combined with other medications, additional signs may occur. These may include wobbliness, weakness, depression, hyperactivity, agitation, disorientation, vocalizing, changes in heart rate, pale gums, tremors, seizures, and increased body temperature, depending on the type of medication.

How is acetaminophen (Tylenol) poisoning diagnosed in a dog or cat?

Acetaminophen poisoning may be suspected when pets develop changes in the red blood cells, signs of liver damage, or other signs consistent with acetaminophen poisoning. Acetaminophen levels in the blood can be measured at a human hospital or specialized laboratory; however, testing for acetaminophen levels is not common. The results may not be returned quickly, and it may be difficult to find a laboratory to run the testing for animals. Since the results may be delayed, treatment is often started without testing if poisoning is suspected.

How is acetaminophen poisoning treated in dogs and cats?

Early decontamination and treatment decrease the risk for serious poisoning. If acetaminophen ingestion occurred within 15–20 minutes, the veterinarian may induce vomiting. Once vomiting is controlled, medical-grade activated charcoal may be administered to decrease absorption of acetaminophen from the gastrointestinal tract. Activated charcoal should only be administered by a veterinarian. Improper administration of activated charcoal may lead to aspiration into the lungs and life-threatening changes in sodium levels.

"Early decontamination and treatment decrease the risk for serious poisoning."

Depending upon the dose ingested, hospitalization may be needed. Fluids may be given under the skin or intravenously. A medicine called N-acetylcysteine is one of the primary treatments. 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 for long-term effects or even death. Pets 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. Pets with liver damage can develop an increased chance of bleeding. These pets may need vitamin K1 or plasma transfusions.

What is the prognosis for recovery with dogs and cats exposed to acetaminophen?

The outcome depends on many factors, including the initial health of the pet, amount ingested, other drugs ingested, and time to treatment. With early treatment, pets are less likely to develop long-term effects. Some pets may have permanent liver damage. Although uncommon, death may occur with high doses or when treatment is delayed. 

What steps can I take to prevent acetaminophen poisoning in my pet?

• Never give any medication to a pet without first consulting a veterinarian.
• Do not leave any medications, including vitamins and supplements, where unattended pets may reach them. It is common for pets to chew through closed bottles. Curious pets may want to check out purses, backpacks, lunch boxes, or suitcases. Some pets will even open lower cabinets or get into open drawers.
• Keep in mind that pets can get on counters or knock items off counters and tables.
• Do not assume a pet will avoid eating medication just because it has a bad taste.
• If you drop a medication on the floor, confine all pets in another area of the home until all the medication can be picked up.

Whenever a toxic exposure is suspected, immediate action is recommended. Early consultation and treatment can help prevent serious health effects.

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.