Paracetamol is a human medication that is sometimes used as a painkiller in dogs. However, very high doses can cause severe problems. Speak to a vet straight away if your dog has ingested an unknown amount of paracetamol or more than the recommended dose.

Paracetamol is also known as acetaminophen. It is the ingredient in products like Calpol, Panadol, and Tylenol, and is part of many flu medicines. When ingested in large amounts, paracetamol may overload the body’s ability to process it. This leads to the accumulation of certain substances that cause damage to the body, especially the liver and red blood cells. Symptoms may start within 1-2 hours or may take up to two days to develop. Immediate, intensive care is required, and recovery may be prolonged.

What is paracetamol intoxication in dogs?

Dog medications go through a series of tests and trials to make sure they are safe and effective in dogs. When specific veterinary medications aren’t available, vets may prescribe certain human medicines for dogs — but only when there’s a clear need and enough evidence to suggest they are safe and effective. Every medication has a safe dose range, where it reliably produces beneficial effects with a low chance of negative effects. The higher above this range, the greater the severity of side effects.

What quantity of medication that is safe depends mostly on body size, species, whether there are other health problems, and whether other medications are being taken at the same time. For the average dog, paracetamol is expected to cause toxic symptoms when they ingest more than 75 mg per kg of bodyweight.

When ingested in very large doses, paracetamol can cause three major problems in dogs:

• Acute liver damage, which can lead to more toxins being produced, and disrupts metabolism and the functions of other organs

• Red blood cells will become unable to distribute oxygen throughout the body, which disrupts every organ in the body, especially the heart and brain.

• Some dogs may also develop dry eye (Keratoconjunctivitis sicca) due to paracetamol intoxication.

Symptoms of paracetamol intoxication in dogs

Symptoms will depend on the organs being most affected.

Liver damage:

• Lack of appetite

• Vomiting

• Lack of energy

• Tummy pain

• Jaundice (yellow tinge to the skin, gums or the white part of the eyes)

• Abnormal behaviours, like pacing, disorientation of pressing the head against a wall

• Seizures

• Coma

Red blood cell damage:

• Dark or bluish gums and tongue

• Fast breathing

• Extreme exercise intolerance

• Brown urine

• Collapse

Dry eye:

Symptoms may not be immediately apparent, especially given the more acute symptoms from other organs. However, early detection and treatment may prevent long-term complications. Symptoms may include:

• Red eye(s)

• Discharge

• Squinting or reluctance to open the affected eye(s)

• Dull, rough appearance to the cornea

• Red blood vessels on the surface of the eye

Dogs at a higher risk of paracetamol intoxication

• Smaller dogs are at greater risk of ingesting a harmful dose of paracetamol, as it takes much less to cause serious health problems.

• Other medications taken at the same time can affect the liver’s ability to process paracetamol effectively.

Diagnosis of paracetamol intoxication in dogs

Paracetamol intoxication is usually diagnosed based on known ingestion and observed symptoms, as there is no readily available test to confirm it.

Routine blood tests that check red blood cells and signs of liver damage will usually detect the consequences of paracetamol intoxication and allow for monitoring of progression.

Veterinary treatment of paracetamol intoxication in dogs

• The first and most important step in treating intoxication is stopping the poison from entering the blood and organs. If a large amount of paracetamol was ingested, the stomach should be emptied as quickly as possible, ideally within 30-90 minutes. This can be done by injection or by pumping the stomach under anaesthesia.

• The next step is administering activated charcoal. This sticks to paracetamol in the gut and prevents it from being absorbed. Large amounts are needed, so a high-strength veterinary product is best. This may be needed for up to three days.

• Dogs are likely to need intensive hospital care for 1-3 days to control the symptoms and help the body eliminate toxic by-products.

• A medication called N-acetylcysteine can be used as an antidote, as it helps the body eliminate the toxic by-products of paracetamol and reduces some of the damage they cause. This often needs to be administered repeatedly for up to two days.

• Medications that protect the liver from oxidative damage, like SAMe and silybin, help contain liver damage.

• Supplemental oxygen by mask or oxygen chamber may help when red blood cells are affected.

• Ascorbic acid may help red blood cells recover and may have some protective effect on the liver.

• If dry eye is present, tear-replacement lubricants help prevent further eye damage.

Home treatment of paracetamol toxicity in dogs

Always contact a vet for advice immediately if you think your pet has ingested a large or unknown amount of paracetamol. Most cases of overdose require immediate emergency care.

Dogs that overcome paracetamol intoxication may require liver support for some time. This may include a special diet for liver patients and medication such as SAMe and silybin.

Prevention of paracetamol intoxication in dogs

• Always store medications in a safe place and out of reach of your pets, even if they don’t look appetising.

• Always check with a vet before giving your pet any medication and follow instructions carefully. If there are any doubts, it’s always best to ask for advice.

• Be very vigilant when giving medicines with food if you have more than one pet.

When to worry about paracetamol intoxication in dogs

Always contact a vet for advice immediately if you think your pet has ingested a large or unknown amount of paracetamol, so the risk can be assessed and treatment advice given.

Speak to a vet for advice if your dog is:

• Vomiting

• Not eating anything

• Drooling excessively

• Behaving abnormally

If your dog develops any of the following symptoms, see a vet as soon as possible:

• Weakness or collapse

• Trouble breathing

• Seizures

• Vomiting and/or diarrhoea with blood

• Abnormal colour in their gums or the white of their eyes