ketoprofen, nonsteroidal anti-inflammatory drug (NSAID) with anti-inflammatory, analgesic, and fever-reducing effects, used to relieve the symptoms of headaches, arthritis, and painful menstruation. Along with ibuprofen and naproxen, it belongs to the propionic acid class of NSAIDs; it apparently acts by inhibiting the body's production of prostaglandins. Available as a prescription drug for more than 20 years in many countries, it was approved as an over-the-counter painkiller in the United States in 1995 and first marketed as Orudis KT. It is considered more powerful than many other NSAIDs. Side effects may include gastrointestinal disturbances and fluid retention.