Aspirin for Dogs and Cats, What’s the Dose?

Pain in Dogs
Ever had a toothache, a backache or a headache? Well chances are your dog has had them too. Dogs also have pain from bite wounds, skin infections, and ear infections. How would you know that your dog is in pain? Look for these signs:

• quits eating
• has less interest in toys or no longer plays
• spends more time sleeping
• pants
• squints
• limps
• hangs its head
• carries itself stiffly
• hunches its back
• trembles, tenses, or flinches when touched
• licks or chews limbs or body parts
• reluctant to move 

Treating Pain with Commonly Prescribed NSAIDS
The most commonly prescribed pain medication for dogs are a group of drugs called NSAIDS or nonsteroidal anti-inflammatory drugs:

• Aspirin
• Rimadyl
• Deramaxx
• Eto-Gesic
• Previcox
• Metacam
• Zubrin

Of all these NSAIDS, aspirin is probably the most commonly used because it is cheap, easily found, and doesn’t require a prescription. Unfortunately, aspirin is also likely to have serious side effects, perhaps more likely than any of the other NSAIDS to have these side effects.

Side Effects of NSAIDS

While there are multiple benefits from NSAIDS, but there are also serious side-effects. These side effects are more likely to cause problems in pets than in people because we’re not very observant and miss the subtle initial signs of problems in our pets. So, if your veterinarian prescribes a NSAID, or any drug for your dog, ask how you can check for side effects, and ask what you should do if side effects occur.

NSAID side effects your veterinarian will discuss include

• stomach ulcers, which may appear as nausea, anorexia, and bloody vomiting
• anemia from blood loss due to gastric ulcers
• lethargy
• panting
• hyperthermia (temperature above 102 F)

Aspirin Toxicity
If the dog receives an aspirin overdose and develops acute aspirin toxicity, side effects include respiratory alkalosis leading to rapid breathing and profound metabolic acidosis. Metabolic acidosis can then progress to cerebral and pulmonary edema, ataxia, seizures, coma and death.

What Aspirin Does in the Body

Aspirin relieves pain (analgesia) and lowers fever. Aspirin works by inhibiting COX-1 and prostaglandin, reducing synthesis of thromboxanes (TXA2). Because prostaglandins and TXA2 can promote pain, fever, and inflammation, aspirin works as an analgesic and antipyretic. Aspirin also prevents platelets from aggregating so it promotes bleeding.

Aspirin Dose and Frequency

Aspirin is prescribed from 10-30 mg/kg of body weight two or three times a day, eight to twelve hours apart.

Buffered aspirin may be better tolerated than regular aspirin.

Human aspirin is 325 mg.

Baby aspirin is 81 mg, about ¼ of the adult aspirin.

 
A dog that weighs 5 lb (2.25 kg) could be given from 22 to 65 mg of aspirin two to three times a day. Consider starting with ¼ baby aspirin (20 mg), doubling to ½ baby aspirin (40 mg) if the low dose doesn’t resolve pain.

A dog that weighs 20 lb (9 kg) could be given from 90 to 270 mg. Consider starting with 1 and ½ baby aspirin (121 mg), increasing to 2 baby aspirin (162 mg) or 3 baby aspirin (243 mg) if lower dose ineffective.

A dog that weighs 50 lb (22.5 kg) could be given from 225 to 675 mg. Consider starting with 3 baby aspirin (243 mg) and increasing to 1 and ½ adult aspirin or (487.5 mg) or 2 adult aspirin (650 mg) if lower dose ineffective.

A dog that weighs 100 lb (45 kg) could be given from 450 to 1350 mg. Consider starting with 1 and ½ adult aspirin or (487.5 mg) and increasing to 2 adult aspirin (650 mg) or 3 adult aspirin (975) if lower dose ineffective.

Which Dogs Should Not Be Given Aspirin?

Do not give aspirin if your dog is not eating, vomiting, or is carrying itself as though it has a stomach ache. Do not give aspirin if your dog is passing stinky, black stools (melena).

Dogs with kidney disease, hypoalbuminemia, or hepatic failure should not be given aspirin. Because aspirin can delay parturition (birthing), pregnant bitches should not be given aspirin in the last few weeks of pregnancy.

Chronic Versus acute Pain

Treating acute or sudden pain, such as a fracture, hit by car, bite wound, or surgery demands a different pain protocol than does chronic pain such as arthritis or disc disease. With acute pain, your veterinarian will prescribe a high dose of pain medication, weaning your pet off as the injury improves. With chronic pain, veterinarians often start with the lowest dose and increase the dose if it isn’t effective. Be sure to ask your veterinarian what signs you’ll see if the pain medication is working, and what you’ll see if the pain medication isn’t working.

Better than Aspirin

There are better pain control techniques for dogs than aspirin because aspirin can have side effects and we often miss the signs of these side effects. I only recommend aspirin in emergency situations. Instead, use the following

• rest
• icing
• heat
• massage
• acupuncture
• chiropractic care
• laser therapy
• fish oil
• Adequan or Ichon
• niacinamide
• tramadol
• amantadine
• gabapentin

Cats and Aspirin
Aspirin is not as safe in cats as it is in dogs, but there are some NSAIDS that can be more safely prescribed for cats, including meloxicam. In cats, aspirin loses its analgesic capacity within a few hours, but endures within the body causing effects in the liver and kidneys for more than a day (38 hours). This is far longer than the half-life of aspirin in dogs (8 hours) or humans (1.5 hours). Because aspirin endures for so long in cats, it cannot be given more often than once every two or three days, but its pain killing benefit will exist for only a few hours on the first day it is given. The high aspirin dose for cats is 5 mg/lb of body weight (10 mg/kg) once every 2-3 days. A baby aspirin is 81 mg, so a 9 lb cat could receive ½ a baby aspirin (45 mg) every Monday, Wednesday, and Friday. The low aspirin dose is 5 mg per cat every third day.

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