Naproxen is a nonsteroidal anti-inflammatory drug (NSAID) used to relieve symptoms of arthritis (eg, osteoarthritis, rheumatoid arthritis, or juvenile arthritis) such as inflammation, swelling, stiffness, and joint pain. People usually use the drug naproxen to relieve pain and swelling, but it can also help treat fever. Naproxen side effects may include headaches, dizziness, and ringing in the ears. Naproxen can help with back pain, but the relief is more modest than many people expect. A large Cochrane review of anti-inflammatory drugs for acute low back pain found that NSAIDs like naproxen reduced pain by only about 7 points on a 100-point scale compared to a placebo. Learn about side effects, dosage, uses, and more for naproxen, which is a generic prescription oral tablet that treats many conditions, such as arthritis. Naproxen is one of a group of medicines called non-steroidal anti-inflammatory drugs (NSAIDs). Naproxen may be prescribed as tablets or as a liquid. During flare-ups it can be especially helpful. It usually starts working within an hour and the effect can last up to 12 hours. Overview: Naproxen is a nonsteroidal anti-inflammatory drug (NSAID) used to relieve pain, reduce swelling, and lower fever. Common side effects include belly pain, upset stomach, heartburn, or. Naproxen is a nonsteroidal anti-inflammatory drug (NSAID) that treats mild to moderate pain and inflammation. It may cause sleepiness, skin reactions or other side effects. Naproxen is a nonsteroidal anti-inflammatory drug (NSAID). It works by reducing hormones that cause inflammation and pain in the body. Naproxen is used to treat pain or inflammation caused by conditions such as arthritis, ankylosing spondylitis, tendinitis, bursitis, gout, or menstrual cramps. Naproxen (Aleve, Naprosyn) may cause heartburn, dizziness, and headaches for some people. Here’s how you can manage common and long-term naproxen side effects. Naproxen is an effective pain reliever, but it can cause side effects, especially if used long-term or at high doses.