Rofecoxib is a nonsteroidal anti-inflammatory drug (NSAID) that has now been withdrawn over safety concerns. Rofecoxib gained widespread acceptance among physicians treating patients with arthritis and other conditions causing chronic or acute pain. Rofecoxib was available on prescription as tablets and as an oral suspension. It was available by injection for hospital use. Cyclooxygenase (COX) has two well-studied isoforms, called COX-1 and COX-2. COX-1 mediates the synthesis of prostaglandins responsible for protection of the stomach lining, while COX-2 mediates the synthesis of prostaglandins responsible for pain and inflammation. By creating "selective" NSAIDs that inhibit COX-2, but not COX-1, the same pain relief as traditional NSAIDs is offered, but with greatly reduced risk of fatal or debilitating peptic ulcers. Rofecoxib is a selective COX-2 inhibitor, or "coxib".