Prostanoids are mediators that have been implicated in all stages of inflammation. The inhibition of prostanoid synthesis by NSAIDs forms the basis of their therapeutic as well as side effects. NSAIDs directly inhibit cyclooxygenase [COX], which leads to reduction of prostaglandin synthesis and also to gastric erosions, inhibition of platelet aggregation and nephrotoxicity. The identification of the two isoforms of COX lead to the hypothesis that COX-2 is responsible for the production of prostaglandins following tissue injury, while COX-1 is involved in normal homeostasis.