Celebrex is a nonsteroidal anti-inflammatory drug (NSAID), specifically a COX-2 inhibitor, which relieves pain and swelling (inflammation).? Celebrex contains the active ingredient Celecoxib which is used to treat mild to moderate pain including menstrual pain and discomfort. It also helps in relieving symptoms of arthritis (osteoarthritis, rheumatoid arthritis, or juvenile rheumatoid arthritis) such as inflammation, swelling, stiffness, and joint pain.