Cyclooxygenase (COX) is an enzyme that converts arachidonic acid into prostaglandins in the arachidonic acid cascade. COX exists in two isoforms, COX-1 and COX-2.
COX-1 is expressed in many tissues, and produces prostaglandins that are involved in protection of stomach lining, maintenance of platelet function, etc.
COX-2 is induced by stimulation with cytokines, growth factors, etc. at inflammation sites, and produces prostaglandins that promote inflammation, pain, and fever.
Non-steroidal anti-inflammatory drugs (NSAIDs) have anti-inflammatory, analgesic, and antipyretic activities through inhibition of COX-2. Conventional NSAIDs inhibit also COX-1, and therefore induce gastrointestinal side effects. To solve this problem newer inhibitors specific to COX-2 have been developed.