See also:

Dog arthritis

Nutraceuticals for dog arthritis

Omega 3 supplements for dogs

Aspirin (dogs only)

Aspirin is ok for dogs, but not for cats. To reduce stomach irritation, use buffered aspirin or give aspirin at mealtime. For chronic arthritis pain, we have prescription drugs that are much safer and far more effective.  Giving your dog aspirin more often than twice a week is a probably a bad idea.  

Use 5 grain (325 mg) aspirin tablets.

A 60 to 80 lb dog may be given one tablet twice a day (every 12 hours) or 1/2 tablet three times a day (every eight hours).  A 30 to 40 lb dog gets half as much; a 15 to 20 lb dog a quarter as much.