Celebrex is prescribed for acute pain, menstrual cramps, and the pain and inflammation of osteoarthritis and rheumatoid arthritis. It is the first of a new class of nonsteroidal anti-inflammatory drugs (NSAIDs) called "COX-2 inhibitors." Like older NSAIDs such as Motrin and Naprosyn, Celebrex is believed to fight pain and inflammation by inhibiting the effect of a natural enzyme called COX-2. Unlike the older medications, however, it does not interfere with a similar substance, called COX-1, which exerts a protective effect on the lining of the stomach. Celebrex is therefore less likely to cause the bleeding and ulcers that sometimes accompany sustained use of the older NSAIDs.

Celebrex has also been found to reduce the number of colorectal polyps (growths in the wall of the lower intestine and rectum) in people who suffer from the condition called familial adenomatous polyposis (FAP), an inherited tendency to develop large numbers of colorectal polyps that eventually become cancerous.