Acetaminophen (Tylenol or Paracetamol) Poisoning in Cats

Key Takeaways

Acetaminophen toxicity is caused by the ingestion of a toxic dose of acetaminophen, also known as paracetamol. 

• Acetaminophen is a common over-the-counter medication used to treat fever and control pain (widely known brands of acetaminophen in North America include Tylenol and Excedrin, but over 200 different products contain this compound)

• Ingestion, even in small doses (50 mg), can be life-threatening to cats and must be treated as an emergency

• If a cat is known or is suspected to have ingested acetaminophen immediate medical attention is warranted

• Physical examination, blood work, and urinalysis are used to confirm acetaminophen ingestion, if the ingestion event was not witnessed

• Treatment is focused on decontamination, reducing organ damage, as well as supportive care

• Early treatment is crucial in improving prognosis

• Some cats develop organ damage that may require long-term treatment or management

A Closer Look: What is Acetaminophen Poisoning in Cats?

Acetaminophen toxicity is a common condition in cats, as many pet parents give their animals acetaminophen-containing drugs in an effort to manage pain or inflammation at home. Acetaminophen toxicity is an emergency: consumption of as little as a quarter of an acetaminophen tablet has the potential to be deadly, depending on the cat’s body weight. If ingestion is known or suspected, immediate veterinarian attention is crucial in improving the cat’s prognosis.

Risk Factors

Symptoms of acetaminophen toxicity vary depending on which tissue is affected. 

Red blood cells are the most common tissue affected in cats; symptoms include: 

• Pale gums • Yellow gums (jaundice) • Difficulty breathing  • Collapse

Liver damage; symptoms include: 

• Loss of appetite • Vomiting • Yellow gums

Kidney damage is not as common in cats as it is in dogs; symptoms include: 

• Loss of appetite • Excessive thirst • Vomiting • Lethargy

Possible Causes

Acetaminophen toxicity is caused by the ingestion of a toxic dose acetaminophen. Once ingested, acetaminophen enters the animal's system. Cats lack the enzyme to break down acetaminophen appropriately. When the compound reaches the liver, it forms toxic metabolites that damage the cat’s red blood cells and liver. 

The potentially lethal dose for cats is 10mg/kg; as little as a quarter of a regular acetaminophen tablet (50 mg) can be deadly for an average-sized cat. There is no safe dose for cats.

Main Symptoms

Symptoms of acetaminophen toxicity develop between 1 and 4 hours after ingestion and include: 

• Weakness • Lethargy • Rapid breathing • Pain when the abdomen is touched • Panting • Vomiting  

• Drooling • Swelling of the paws or head • Brown gums  • Chocolate-colored urine

Testing and Diagnosis

If ingestion of acetaminophen is witnessed, the diagnosis is self-evident. In some cases, ingestion can occur without a witness. 

A cat suspected of having ingested acetaminophen will undergo the following diagnostics:

• Physical examination • Blood tests  • Urinalysis

Steps to Recovery

If the ingestion is known to have occurred and treatment is sought rapidly, the objective of treating acetaminophen toxicosis is removal of the toxin.  

Induced vomiting: emesis is the most effective way to decontaminate the GI system. There is no safe way to induce vomiting at home.

Gastric lavage: gastric lavage involves rinsing the stomach contents through a tube passed from the mouth into the stomach

Activated charcoal: activated charcoal can be administered to slow the absorption of acetaminophen. Activated charcoal must be administered by a veterinarian, as its improper administration can be aspirated into the lungs and cause life-threatening changes in sodium levels.

N-acetylcysteine (NAC): administration of NAC reduces the extent of liver damage caused by acetaminophen. NAC binds to the acetaminophen metabolite and helps its elimination. 

Following decontamination and NAC treatment, monitoring is required for up to 48 hours, including repeated blood work to catch any signs of organ damage quickly.

If ingestion was not witnessed but symptoms lead to suspicion of toxicity, treatment is targeted at reducing organ damage and may include fluid therapy and blood transfusions. 

If treatment is sought early, prognosis is good. Cats with severe liver damage have a very poor prognosis, and may have life-long liver function abnormalities. If untreated, acetaminophen toxicity can be fatal.

Prevention

Acetaminophen toxicity is completely prevented by removing the possibility of ingestion of acetaminophen. Strategies include:

• Diligent storage and disposal of medications 

• Always contacting a veterinarian before administering any kind of drug to pet

Is Acetaminophen Poisoning Common in Cats?

Acetaminophen toxicity is fairly common in cats because pet parents may give their cats acetaminophen in an effort to treat pain or inflammation at home, not knowing that it is toxic.

Typical Treatment

• Gastrointestinal decontamination • N-acetylcysteine