By Rania Gollakner, BS, DVM


Over-the-counter medications can cause serious side effects in your pet. Contact your veterinarian before using any over-the-counter medication and follow your veterinarian’s directions.

What is aspirin?

Aspirin or acetylsalicylic acid (brand names: Ecotrin®, Aspirin®, and others) is an anti-inflammatory, anti-clotting, fever-reducing, and pain control medication, used most commonly for its anti-clotting effects in many pets.

Its use in cats, dogs, and small mammals to treat excessive clotting, inflammation, fever, and pain is 'off label' or 'extra label'. Many drugs are commonly prescribed for off label use in veterinary medicine. In these instances, follow your veterinarian’s directions and cautions very carefully as their directions may be significantly different from those on the label.

How is aspirin given?

Aspirin is given by mouth in the form of a tablet, preferably an enteric-coated tablet. Give with food. This medication should take effect within 1 to 2 hours; however, effects may not be visibly obvious and therefore laboratory tests may need to be done to evaluate if this medication is working.

What if I miss giving my pet the medication?


Are there any potential side effects?

The most common side effects are gastrointestinal effects, such as nausea, decreased appetite, vomiting, or intestinal irritation. Bleeding of the gastrointestinal (GI) tract may also occur, even at therapeutic doses. Signs of bleeding in the GI tract include black/tarry stools, blood or ’coffee grounds’ in the vomit, or frank blood in the stools. In severe bleeding cases, anemia or low blood protein can occur. In cats, aspirin may cause acidosis.


It is important to dose your cat carefully as cats are very sensitive to aspirin. Because aspirin clears more slowly from a cat’s system, if dosed incorrectly, it can build up in your cat’s system and cause toxic effects. Kidney and liver damage can occur. Follow your veterinarian’s instructions carefully.

Are there any risk factors for this medication?

Aspirin should not be used in pets that are allergic to it, or pets that have bleeding ulcers, bleeding disorders, asthma, or kidney failure. Use caution in pets that have severe liver failure, decreased kidney function, or have low blood protein. If possible, aspirin should not be used one week prior to surgical procedures.

It must be used cautiously and dosed very carefully in cats and newborn pets. Aspirin should not be used in pregnant animals unless it is a last resort.

Are there any drug interactions I should be aware of?

The following medications should be used with caution and are sometimes contraindicated when given with aspirin: ACE inhibitors, alendronate, aminoglycosides, SSRI antidepressants, blood glucose lowering agents, calcium channel blockers, corticosteroids, carbonic anhydrase inhibitors (especially dichlorphenamide), digoxin, furosemide, glucosamine, heparin, oral anticoagulants, hyaluronidase, methotrexate, NSAIDs, pentosane polysulfate sodium, phenobarbital, probenecid, sulfinpyrazone, spironolactone, tetracycline, tiludronate, urinary acidifying or alkalinizing drugs, valproate products, or vitamin E.



Your veterinarian may monitor your pet to be sure that the medication is working. If needed, your veterinarian may monitor for bleeding or anemia. Monitor for side effects and contact your veterinarian if side effects are noted.

How do I store aspirin?

Aspirin should be stored in a tight container, away from light and moisture. If the medication has a vinegar-like odor, do not use it.

What should I do in case of emergency?


Free First Exam

Our pet care experts can't wait to welcome you. 

Find a Local VCA

We're here for you and your pet in 43 states. 
Loading... Please wait