Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) used to relieve mild to moderate pain from various conditions such as headache, dental pain, menstrual cramps, and muscle aches. It works by blocking the bodys production of certain natural substances that cause inflammation, which helps to decrease swelling, pain, or fever. Mefenamic acid is usually taken with food every 6 hours as needed for up to 1 week. It is important to follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Mefenamic acid is also used to relieve menstrual pain (pain that happens before or during a menstrual period) . It is approved to treat pain in people who are at least 14 years old for no longer than seven days, and to treat menstrual cramps for no longer than two to three days. Mefenamic acid belongs to a group of medications called NSAIDs, and taking it with other NSAIDs can increase the risk of stomach bleeding and ulcers. It is important to read the Medication Guide provided by your pharmacist before you start taking mefenamic acid and each time you get a refill, and to talk to your doctor or pharmacist if you have any questions.