Ketoprofen is used to relieve pain, tenderness, swelling, and stiffness caused by osteoarthritis (arthritis caused by a breakdown of the lining of the joints) and rheumatoid arthritis (arthritis caused by swelling of the lining of the joints). Prescription ketoprofen capsules are also used to relieve pain, including menstrual pain (pain that occurs before or during a menstrual period). Nonprescription ketoprofen is used to relieve minor aches and pain from headaches, menstrual periods, toothaches, the common cold, muscle aches, and backaches, and to reduce fever. Ketoprofen is in a class of medications called NSAIDs. It works by stopping the body's production of a substance that causes pain, fever, and inflammation.