i had a dog on Rimadyl and I had to take him off after 2 weeks, he kept vomiting and I knew his liver was being affected. Our drugstores carry an aspirin just for dogs, our vets will tell us to just go to any drugstore and ask for it and they will know. Seems to work as well as the stronger meds, side effects are nil, they are coated. Bonus is they are not expensive.