Ibuprofen is a nonsteroidal anti-inflammatory drug (NSAID) used to relieve pain, reduce inflammation, and lower fever. It is commonly used for headaches, muscle aches, arthritis, menstrual cramps, and minor injuries. Available over-the-counter in tablets, capsules, and liquid forms, ibuprofen works by blocking the production of prostaglandins, chemicals in the body that cause pain and inflammation.