Aspirin is a first-line treatment for the fever and joint-pain symptoms of acute rheumatic fever . The therapy often lasts for one to two weeks, and is rarely indicated for longer periods. After fever and pain have subsided, the aspirin is no longer necessary, since it does not decrease the incidence of heart complications and residual rheumatic heart disease.   Naproxen has been shown to be as effective as aspirin and less toxic, but due to the limited clinical experience, naproxen is recommended only as a second-line treatment.  
Cats are much more sensitive to aspirin poisoning than dogs. Signs of aspirin poisoning in dogs or cats include gastrointestinal signs (., vomiting, diarrhea, vomiting of blood, black-tarry stool, stomach ulcers, etc.), hyperthermia, respiratory changes, bone marrow suppression, kidney failure, and central nervous system signs (., collapse, extreme weakness, tremors, seizures, cerebral edema). Aggressive treatment is necessary with toxic amounts, and includes decontamination, gastrointestinal protectants, symptomatic and supportive care, IV fluids, and blood work monitoring.
Prescription NSAIDs are an important treatment for the symptoms of many debilitating conditions, including osteoarthritis, rheumatoid arthritis, gout and other rheumatological and painful conditions. OTC NSAIDs are used to temporarily reduce fever and to treat minor aches and pains such as headaches, toothaches, backaches, muscular aches, tendonitis, strains, sprains and menstrual cramps. Common OTC NSAIDs include ibuprofen (Motrin, Advil) and naproxen (Aleve). In addition, some combination medicines that relieve various symptoms, such as multi-symptom cold products, contain NSAIDs.