DRUG CLASS AND MECHANISM: Celecoxib is a nonsteroidal anti-inflammatory drug (NSAID) that is used to treat arthritis, pain, menstrual cramps, and colonic polyps. Prostaglandins are chemicals that are important contributors to the inflammation of arthritis that causes the pain, fever, swelling and tenderness. Celecoxib blocks the enzyme that makes prostaglandins (cyclooxygenase 2), resulting in lower concentrations of prostaglandins. As a consequence, inflammation and its accompanying pain, fever, swelling and tenderness are reduced. Celecoxib differs from other NSAIDs in that it causes less inflammation and ulceration of the stomach and intestine (at least with short-term treatment) and does not interfere with the clotting of blood. NSAIDs have been found to prevent the formation and reduce the size of polyps in patients with the genetic disease, familial adenomatous polyposis (FAP). In FAP, patients develop large numbers of polyps in their colons, and the polyps invariably become malignant. The only cure of FAP requires removal of the entire colon. Celecoxib is approved as an adjunctive (secondary) treatment among patients with FAP. The cramping and pain during menstrual periods is due to prostaglandins, and blocking the production of prostaglandins with celecoxib reduces the cramps and pain.