The weight of the animal determines the aspirin dosage in canines, and dosages usually range from 5 to 10 milligrams per pound twice daily, states PetPlace. Generally, adult human aspirin tablets are 325 milligrams, and low-strength tablets are 81 milligrams.
Aspirin, or acetylsalicylic acid, is an over-the counter medication veterinarians typically give to dogs to treat minor arthritis inflammation and pain, explains PetPlace. The chemical composition of aspirin can irritate a dog's stomach lining, even if the aspirin is in coated tablet form. Other aspirin side effects include vomiting of food or blood, suppressing of appetite, stomach bleeding, diarrhea, and black bowel movements. Dog caretakers should consult a veterinarian before administering aspirin.