MedicineNet lists naproxen 500 milligrams as a nonsteroidal anti-inflammatory drug (NSAID) used to treat pain, inflammation and fever as well as osteoarthritis, rheumatoid arthritis, ankylosing spondylitis and painful menstrual periods. The drug decreases users' levels of prostaglandins, chemicals responsible for pain, inflammation and fever.
According to Drugs.com, naproxen is the active ingredient in Anaprox, Midol Extended Relief, Naprosyn and Aleve. Aleve is available in smaller doses and without a prescription. Dosages range from 250 milligrams every six to eight hours for mild pain to 1,000 milligrams every 12 hours for the treatment of arthritis and chronic conditions.
Pregnant and nursing women should avoid naproxen because it can cause pass into breast milk and cause birth defects. Patients should always discuss their medical histories with health professionals before taking NSAIDs.