Aspirin for Cats

Aspirin is a well-known anti-inflammatory pain reliever and fever reducer for humans, but it's also sometimes given as an over-the-counter treatment for pain in felines. The active ingredient in aspirin is acetylsalicylic acid, a chemical compound first discovered in willow bark.

Aspirin is an oral medication that comes in two forms: uncoated and enteric-coated tablets. When ingested, aspirin inhibits the enzyme cyclooxygenase, a precursor to prostaglandins, which are hormone-like compounds responsible for pain and blood clotting. By suppressing the synthesis of prostaglandins, aspirin is able to thin the blood and relieve pain.

Dosage

The standard dosage of aspirin for cats is 6 to 10 milligrams per kilogram of body weight. However, since cats metabolize aspirin slowly, you should only give this medication every 48 to 72 hours. 

Dosage instructions

Aspirin can damage the stomach lining, so it’s essential that you give it with meals. Some vets suggest using coated tablets to minimize this effect. Enteric coatings dissolve in the intestinal tract rather than the stomach to minimize damage to the stomach lining. 

Efficacy

Since aspirin is an off-label treatment for felines, there haven’t been any direct studies of its efficacy in cats. However, according to Merck Veterinary Manual, aspirin’s antiplatelet effects are helpful for treating thromboembolic disease, a common blood clotting disorder in felines. 

Aspirin effectively treats clotting disorders because of its effects on the prostaglandin thromboxane, which is involved in the constriction of blood vessels and platelet clumping. For this reason, doctors and vets commonly prescribe low-dose aspirin for patients who are predisposed to blood clots. 

Side Effects

According to Merck Veterinary Manual, side effects are common for animals taking aspirin, though the severity depends on the dosage strength. Usually, the side effects are mild, with nausea and decreased appetite being the most common complaints from pet owners. Other side effects of aspirin for cats include: 

• Vomiting

• Irritation of the stomach lining

• Stomach ulcers

• Thinning of the blood
  

• Slowed blood clotting

• Stomach acidity

• Refusal of food

• Blood in the feces or vomit

• A reduction in blood supply to the kidneys

Considerations

Pet parents must be cautious with this drug. Cats can easily overdose on this medication, which can cause salicylism since their body removes aspirin at a slower rate than dogs and humans. 

Experts advise against giving this medication if your feline has GI ulcers, bleeding disorders, or kidney or liver problems. Cats with liver and kidney problems have a harder time excreting aspirin from the body. Also, pregnant felines shouldn’t be given aspirin during late pregnancy since this medication can cause congenital deformities and disabilities.

Due to its blood-thinning effects, aspirin cats should not take this medication a week prior to undergoing surgical procedures. Additionally, vets advise that cats with low albumin levels take microdoses of aspirin rather than the normal recommended amount. 

Drug Interactions

Aspirin is known to interact with certain drugs and may inhibit or increase their effects. Tell your vet if your feline is taking any of the following medications:

• Anticoagulants (warfarin, sintrom, heparin)

• Diabetes medications from sulfonylurea derivates (glimepiride [amaryl], gliquidone [glurenorm])

• Certain immunosuppressants (methotrexate)

• Digitalis Glycosides (digoxin)

• Sulphonamides (bactrim, septra)

• Valproic acid (depakote, depacene)

• Certain antibiotics and sulphonamides (penicillin, sulfamethoxazole, tetracycline, biseptol) 

• NSAIDs (ibuprofen, diclofenac, indocin, celebrex)

• Diuretics (furosemide and spironolactone)

• Vitamin E

• SSRI antidepressants (paroxetine, escitalopram, and sertraline)

• Calcium channel blockers (amlodipine, diltiazem)

• Barbiturates (phenobarbital)

Allergic Reactions and Sensitivity

Cats are inherently sensitive to aspirin due to their slow metabolism of the drug — this is why vets recommend waiting 48 to 72 hours between doses. Symptoms of an aspirin overdose in cats include:

• Coma

• Changes in breathing

• Fever

• Lethargy

• Liver damage

• Slowed blood clotting

Cats can develop an allergy to aspirin. Symptoms of an aspirin allergy usually manifest within an hour of taking the medication. 

Symptoms of an allergy to aspirin include:

• Swelling of the mouth, tongue, or face

• Scratching

• Trouble breathing

• Hives

Frequently Asked Questions

How do you store this medication?

Store aspirin in its original, airtight container in a dry, dark area. 

What should I do if my pet has a reaction to aspirin?

If you suspect your feline is having an allergic reaction or overdose from aspirin, seek veterinary care immediately.

What should I do if I miss a dose of aspirin?

Give your cat their dose as soon as you remember, and give them their next dose at least 48 hours later. Never double up a dose or give your cat aspirin more often than every 48 hours.

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