The active ingredient in Aleve is naproxen sodium, according to Drugs.com. It is a nonsteroidal anti-inflammatory, or NSAID, that is used to relieve a variety of conditions, including headache, tendonitis, dental pain, muscle aches and cramps associated with menstruation. It also reduces swelling and stiffness in the joints that is associated with gout, bursitis and arthritis.
Naproxen sodium works by blocking the production of certain substances in the body that cause inflammation and swelling. It is usually taken by mouth two or three times each day along with a full 8-ounce glass of water. WebMD warns not to lie down for at least 10 minutes after taking naproxen sodium. Because it can cause stomach upset, it is recommended to take it with milk, food or in conjunction with an antacid medication.
WebMD recommends taking naproxen sodium at the lowest dose possible in order to avoid the risk of stomach bleeding and other potential side effects. It can take a couple of weeks for improvement of symptoms after naproxen sodium therapy has begun, particularly for conditions like arthritis, so it is important to take the full dose recommended even if no signs of immediate improvement are evident at first.