It is possible to give cats aspirin but there are dosage limits. Never give a cat more than half of a children's 81mg tablet every two days, according to All Feline Hospital. Any more could be fatal.
Cats do not metabolize aspirin in the same way that humans do, so it is always best to go to a vet if your cat is sick. Ibuprofen and Tylenol are both poisonous to cats and can cause death without immediate treatment. If your cat has consumed aspirin, signs such as loss of appetite, vomiting, diarrhea, weakness and a lack of co ordination may be observed and immediate emergency medical treatment should be sought.