Acetaminophen (paracetamol) in Pets

Why even part of a paracetamol tablet is dangerous for cats: Merck's 10 and 40–50 mg/kg figures, the signs that appear within hours, and what to do now.

What It Is

Acetaminophen, sold as paracetamol outside North America, is a common human pain and fever medicine. Cats lack enough of the liver enzymes (glucuronyl transferases) that normally make it harmless, so a toxic by-product builds up. In cats this mainly damages red blood cells, turning haemoglobin into methaemoglobin that cannot carry oxygen. In dogs high doses mainly damage the liver.

Where Pets Come Across It

Tablets dropped on the floor, a well-meaning owner giving a human pill for pain, and combination cold and flu products that include acetaminophen. A single regular tablet usually contains 325–500 mg.

Which Animals Are Affected

Cats are extremely sensitive. Ferrets are also sensitive. Dogs tolerate more but can still be poisoned.

Published Toxic Dose

The Merck Veterinary Manual states that toxicosis in cats generally occurs at 40–50 mg/kg, but some cats have shown signs at 10 mg/kg; in practice there is no safe dose for cats. Dogs usually show no signs below 100 mg/kg, with methaemoglobinaemia reported above 200 mg/kg.

Acetaminophen (paracetamol) Dose Exposure Calculator

Enter your pet's weight and estimated quantity missing to compare against veterinary literature thresholds.

Affected Species Dog (Canine) Cat (Feline)

Pet Body Weight

kg lb

Tablet Strength Regular Strength (325 mg) Extra Strength (500 mg)

Number of Tablets Swallowed

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Signs and How Soon They Appear

In cats, signs start within 1 to 4 hours: brown or blue-grey gums, fast or laboured breathing, swelling of the face and paws, drooling and depression. Liver injury may follow over 1 to 3 days. Dogs more often show vomiting, then signs of liver damage over 24 to 72 hours.

What to Do Right Now

Never give acetaminophen to a cat. If a cat has swallowed any amount, go to a vet immediately; hospital treatment works well when it starts early. Bring the packet. Do not try to make your cat vomit at home.

Frequently Asked Questions

Sources and References

• Merck Veterinary Manual: Toxicoses from Human Analgesics
• Pet Poison Helpline: Acetaminophen

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