Naproxen is a medication that is licensed to reduce pain and inflammation caused by various conditions, such as injury, arthritis, and menstrual cramps. By inhibiting the action of certain hormones that cause inflammation and pain in the body, the medicine is effective in: reducing pain related to bone, muscle, or tendon injury or inflammation; reducing fever; and alleviating pain and joint swelling associated with different forms of arthritis and other diseases. Naproxen is available as either an over-the-counter or prescription drug and comes in tablet, caplet, and liquid forms.