Naprosyn Naproxen Naprosyn (Naproxen) is a Non-Steroidal Anti-Inflammatory Drug (NSAID) used to relieve pain and swelling (inflammation). It is also used to treat headaches, muscle aches, backaches, tendonitis, bursitis, dental pain, menstrual cramps, arthritis, or gout. Generic Naprosyn may be used to reduce fever, or relieve minor aches and pain due to the common cold or flu. It may be used to treat other conditions as determined by your doctor. This medicine works by blocking the enzyme in your body that makes prostaglandins. Decreasing prostaglandins helps to reduce pain, swelling, and fever.