Aspirin has been used by dog owners in the past although it is not recommended by most vets, as a range of drugs with fewer side effects are now available. The standard dose of aspirin is 5mg/lb of body weight (so for a 100lb dog that would be about one and a half standard aspirin) twice a day and should always be taken with food. Aspirin, like many NSAID (non-steroidal anti-inflammatory dugs) can cause many serious side effects including include vomiting, loss of appetite, depression, lethargy, and diarrhoea, kidney and liver problems and ulcers. It can also interact with other prescription medication so you should always consult with a vet before administering aspirin. 


There are several NSAIDS which are more suited for dogs such as meloxicam, caprofen and deracoxib. If your vet does recommend aspirin or any other NSAID for your dog then you should watch closely for symptoms such as changes in urination habits, odour or colour, loss of appetite, vomiting and black or tarry stools. Other human painkillers such as Panadol and paracetamol have also previously been used in animals but can have even more serious side effects than aspirin.


Uses for Aspirin
Dogs are most commonly given aspirin for treatment of arthritis and associated joint pain. There may be other situations where your dog is in pain, where aspirin may give relief.

Aspirin has good anti-inflammatory effects that reduces swelling. It can also reduce pain and fever. These effects will help make your dog more comfortable.

Note that a dog is not a human. Just because your dog "does not feel good" is not a reason to give it an aspirin. Usually, aspirin is given to relieve extreme conditions of discomfort. Also note that most vets prescribe Rimadyl as a better pain-killer and anti-inflammatory than aspirin.

Use caution
You should use caution in administering any medication to a pet, because too much may be toxic, the medicine may not be tolerated, or it can cause an upset stomach or ulcers in the animal.

Can be toxic
It can be toxic if given in high doses of about 30 mg per pound of the dog. This means that even baby aspirin could be poisonous for dogs weighing two pounds or less. An adult aspirin which is 320 mg. would be toxic for a 10-pound dog. To be sure that you are using the aspirin for the right reason and at the right dose, you should consult your veterinarian first.

Not for young dogs or cats
Aspirin is poorly tolerated by young dogs, since they lack the enzymes necessary to process the aspirin. The same is true for most cats.

Upset stomach
Aspirin can cause gastrointestinal upsets and ulcers in dogs, just as in humans. You should pay attention to your dog's eating habits when administering aspirin to watch for signs of an upset stomach. If there are any signs of ulcers, such as blood-tinged vomiting, it is important to stop the aspirin.

Giving the aspirin with food and using buffered aspirin is the best to prevent stomach problems.

I prefer to grind up the aspirin and put it in some food to make sure it does not irritate the stomach lining.

No Tylenol
You should not give your dog such products as Tylenol as a substitute for real aspirin. Some people say their vet prescribed Tylenol, but most sources say it should not be given to animals.

Recommended dosage
Most veterinarians recommend between 5 mg and 10 mg per pound of the dog's weight every 12 hours. Going on the safe side, a recommended dosage of aspirin of about 5 mg/lb seems to work well for most dogs. If you are going to give more, it is a good idea to check with your vet. Also, note that a small dog should take less per pound.

Enteric coated aspirin is not recommended in dogs because about half the time the coating isn't digested and the aspirin is excreted whole in the stool.

Start small
It is better to start off small and work your way up to the maximum. If the dog has relief with a smaller dosage, that is great.

A standard aspirin is 320 mg. A baby aspirin is typically 80 mg. That means that 5 mg/lb works out to be one baby aspirin per 16 pounds of body weight twice a day.

The following chart can be used as a guide. Note that this is not medical advice.

Weight of dog Number of tablets each 12 hours mg
8 lbs [3.62 kg]

½ baby aspirin or less

40 mg
16 lbs [7.25 kg]

1 baby aspirin

80 mg
32 lbs [14.50 kg]

½ adult or 2 baby

160 mg
48 lbs [21.75 kg]

&frac34 adult or 3 baby

240 mg
64 lbs [29.00 kg]

1 adult or 4 baby

320 mg
80 lbs [36.30 kg]

1¼ adult or 5 baby

400 mg
96 lbs [43.55 kg]

1½ adult or 6 baby

480 mg

In conclusion
The proper dosage of aspiring can give your dog relief from pain and inflammation. You should be aware of possible problems and know the proper dosage. It is good to check with a vet before giving any medication, and remember that dogs are not humans and don't need an aspirin for minor pains.

By Ron Kurtus (revised 21 May 2004)
School For Champions

  • NEVER EVER give Tylenol (toxic to liver) or ibuprofen (Nuprin, Motrin, Advil, etc.). Ibuprofen is very toxic and fatal to dogs at low doses. Only aspirin is safe for dogs, and buffered aspirin or ascriptin is preferred to minimize stomach upset.

  • When giving a dog aspirin always check the dogs stool. Look for black stools which can indicate occult bleeding, and then discontinue aspirin immediately (use a buffered aspirin instead). The coated aspirins are not readily digestible by canines, and are often passed through with little but the coating having been digested.

  • Aspirin may also cause birth defects, so it should not be given to pregnant animals.


What is acetylsalicylic acid (ASA) toxicosis? 

ASA, the chemical name for aspirin, is sometimes administered to animals to relieve minor pain and discomfort. ASA toxicity is the poisoning of the animal due to overdose or to long-term use. It can lead to severe kidney and liver malfunction, blood abnormalities, fluid imbalance, and dehydration. Toxicity or poisoning occurs more often in cats than dogs. 

What causes ASA toxicosis? 

Aspirin toxicity occurs when an animal accidentally ingests aspirin or when human dose guidelines are used for cats. Toxicity can also occur with repeated aspirin administration. 

What are the signs of ASA toxicosis? 

The animal will appear depressed (sluggish, less alert). Your pet may vomit blood due to bleeding in the stomach. It may have fast respirations, high body temperature, muscle weakness, and be unsteady when standing or walking. Without treatment, coma and death may occur.

How is ASA toxicosis diagnosed? 

Aspirin toxicity is diagnosed by a thorough history and physical examination and by laboratory tests. Any history of pain (or other) medication ingestion, especially within 5 days of the development of signs, is important information for the veterinarian. Complete blood counts (CBCs) will reveal blood abnormalities such as anemia (low red blood cell count), and blood chemistries will often show changes reflecting fluid and electrolyte imbalance. Other lab tests may be done. For example, salicylic acid, a component of aspirin, may be found in the blood. 

How is ASA toxicosis treated? 

A specific antidote to counteract the effects of aspirin is not available. Pets are treated using the general principles of supportive care for poisoning. The veterinarian may attempt to empty the stomach by inserting a tube down the throat and flushing it out with a solution (gastric lavage). Another way of emptying the stomach is by inducing vomiting by the administration of drugs (emetics) that cause the animal to vomit. The animal may need intravenous fluids (through a vein). The initial goal is to maintain kidney function and fluid-electrolyte balance because severe dehydration and severe fluid imbalance can occur. 

What is the prognosis of animals with ASA toxicosis? 

The outcome depends on the amount of aspirin ingested and the rapidity of treatment. If the toxicity has progressed to toxic hepatitis (inflammation of the liver), severe blood abnormalities, or coma, the prognosis is usually poor. 

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