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 or ASA (brand names: Ecotrin®, Aspirin®, and others) is an anti-inflammatory, anti-clotting, fever-reducing, and pain controlling 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 obvious and so laboratory tests may need to be done to evaluate if this medication is working.

What if I miss giving my pet the medication?

If you miss a dose, give it when you remember. However, if it is close to the time for the next dose, skip the dose you missed, give it at the next scheduled time, and return to the regular dosing schedule. Never give your pet two doses at once or give extra doses.

Are there any potential side effects?

The most common side effects are gastrointestinal, 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.

This moderate-acting medication should stop working in a few days, although effects can be longer in pets with liver or kidney disease.

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.

Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking.

Is there any monitoring that needs to be done with this medication?

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 you see any.

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?

If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions for contacting an emergency facility.

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