Defining COX-2 inhibitors.

Arachidonic acid metabolism is governed by 2 isoforms of cyclooxygenase (COX), the constitutively expressed COX-1 and the inducible COX-2. Antiinflammatory, analgesic, and antipyretic effects of nonsteroidal antiinflammatory drugs (NSAID) are explained by the capacity of these agents to inhibit COX-2, whereas the serious gastrointestinal side effects are caused by inhibitors of COX-1. The first of a new class of COX inhibitors, the COX-2 specific inhibitors, has just been approved for the treatment of osteoarthritis (OA) and rheumatoid arthritis (RA). As the clinical outcomes of specific COX-2 inhibitors are considerably different than those of NSAID, it is essential for the clinician to understand the basis of classification of those new, effective, and safer therapeutic agents for the treatment of OA and RA.