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Why Is Acetaminophen (Tylenol) so Toxic?

Why Is Acetaminophen (Tylenol) so Toxic?

HomeEmergenciesFoods/Substances • Acetaminophen (Tylenol)

Acetaminophen is the active ingredient in Tylenol and some other related medications that are used to treat pain and fever in people. This drug is extremely toxic and potentially fatal especially for cats and dogs can suffer severe liver toxicity.

Acetaminophen is mostly metabolized by the liver. Cats are at much greater risk of toxicity than dogs because they lack certain proteins necessary for the liver to safely metabolize acetaminophen.  The Tylenol takes up space in the cat’s hemoglobin molecule causing a condition called Methemoglobinemia.   This means that the blood can no longer supply adequate amounts of oxygen to the body’s vital organs. Its lack of oxygen-carrying ability changes the color of blood from red to brown.

Most cases of acetaminophen toxicity in dogs and cats are accidental. A pet may find and chew on a bottle of pills or eat a pill that has fallen on the floor. Sadly, some cases occur because pet owners give medication intended for people to their pets without being instructed to do so by a veterinarian.
Cats are 7 to 10 times more susceptible to acetaminophen toxicity than dogs are. Because cats are extremely sensitive to the drug’s toxic effects, acetaminophen is never given to cats. However, it’s definitely not recommended for dogs, either, because of the potential for liver toxicity.

What Are the Clinical Signs of Acetaminophen Toxicity?

The main clinical signs associated with acetaminophen toxicity that result from liver injury and an inability of the blood to carry oxygen include:

  • Vomiting
  • Decreased appetite
  • Lethargy (tiredness)
  • Difficult or rapid breathing
  • Abdominal pain
  • Brown discoloration of the gums (a result of methemoglobin)
  • Brown urine
  • Blue gums (known as cyanosis, indicates inadequate oxygen supply)
  • Swelling of the face or paws
  • Shock, collapse, death

What Is the Treatment for Pets Suffering from Acetaminophen Toxicity?

There is a specific antidote for acetaminophen toxicity. This medication, N-acetylcysteine, limits formation of the toxic substance that damages the liver and red blood cells.  Additional treatments may include blood transfusions, intravenous fluid therapy, and other medications to help support and stabilize the patient.  Jefferson Animal Hospital is prepared to diagnose and treat your pet if they accidentally gain access to Tylenol.   But prevention is best.

KEEP ALL HUMAN MEDICATIONS OUT OF REACH OF CHILDREN AND PETS.