Acetaminophen is a medication commonly used to alleviate fever and pain. Common brands include Tylenol®, Percoset®, aspirin free Excedrin®, Feverall®, Liquiprin®, Panadol®, Tempra®, Pamprin®, Midol® and various sinus, cold and flu medications. It is often found in combination in cold and flui products – many of which are labeled as "aspirin-free".
Acetaminophen is available in various formulations including tablets, liquids, liquigels, rectal suppositories and chewable tablets. It also comes in a variety of strengths per unit including children's strength (80 mg), junior strength (160 mg), regular strength (325 mg), extra strength (500 mg), and various strengths of infant and children's elixirs.
Cats are much more sensitive to acetaminophen than dogs and are therefore more susceptible to acetaminophen toxicity. One regular strength acetaminophen tablet is toxic and potentially lethal to a cat.
In addition to severe liver failure, acetaminophen causes damage to red blood cells. These include:
What to Watch For
The symptoms of acetaminophen toxicity develop in stages. Symptoms may occur more quickly or slowly depending on the amount ingested.
Prompt veterinary care is crucial to surviving the toxic effects of acetaminophen. If treatment is instituted soon after ingestion there is a greater chance of survival regardless of the amount ingested.
The diagnosis of acetaminophen toxicity is generally based on physical exam findings and a history of access or exposure to acetaminophen.
Blood levels of acetaminophen can be analyzed, but the results may not be received for hours to days. Determination of methemoglobin levels can help determine how long treatment will be necessary and may help determine prognosis. However not all veterinary clinics have the ability to measure the methemoglobin level. Methemoglobin levels can sometime be estimated by dropping a sample of blod in to white filter paper. If the blood is brownish in color, it is roughly estimated that the methemoglobin level is more than 15% (normal is less than 1%). Levels starting at 20% cause difficulty breathing and 40% can cause mental depression.
Baseline laboratory work including a complete blood count, diagnostic profile, and urinalysis may be completed to determine your pets overall health.
Treatment is typically started as soon as the diagnosis is suspected, often in the absence of diagnostic tests. Blood work may be done to evaluate the current function of the liver and the level of red blood cells and hemoglobin.
Prognosis for survival is based on how quickly the cat receives treatment following ingestion of a toxic amount of acetaminophen.
The prognosis for acetaminophen toxicity is good if caught early in the disease. Early vomiting and decontamination with activated charcoal prior to onset of clinical signs generally provides good prognosis. Once clinical signs are present, the prognosis is variable depending on the severity of the methemoglobinemia, hemolysis and liver damage.