Etoricoxib did not inhibit the gastric synthesis of prostaglandin and had no effect on platelet function. Cyclooxygenase is responsible for the prostaglandin synthesis. Were identified two different isoforms of cyclooxygenase, COX-1 and COX-2. It has been shown that COX-2 is the major enzyme responsible for the synthesis of prostanoid mediators involved in pain, inflammation and fever.