It or to sulfa drugs. It or to sulfa drugs. The body called cyclo-oxygenase. If you have certain medical conditions. Celebrex is approved for the relief of pain, fever, swelling, and tenderness caused by osteoarthritis, rheumatoid arthritis, and ankylosing spondylitis. Celebrex is approved for the relief of pain, fever, swelling, and tenderness caused by osteoarthritis, rheumatoid arthritis, acute pain, painful menstruation and menstrual symptoms, and to reduce numbers of colon and rectum polyps in patients with familial adenomatous polyposis. Celebrex works by blocking the action of a substance in the body called cyclo-oxygenase.