I've given ecotrin (aspirin w/a coating to protect the stomach) as prescribed by my vet to my dogs before. Recently Sofie (an 11 year old lab/Airedale mix) tore her ACL we gave her ecotrin and the vet had us switch to Rymidal a prescription pain reliever that doesn't thin the blood. This was important since she had surgery a few weeks later. What ever you do don't use Tylenol or Advil/Motrin, those are very dangerous for dogs.