Pain is one of the commonest symptoms in many patients. The common causes of pain include musculoskelet al conditions like osteoarthritis and rheumatoid arthritis. (1) Nonsteroidal antiflammatory drugs (NSAIDS) are the first line drugs used in the treatment of such patients for alleviation pf pain. The principal mechanism of action of NSAIDS is via the inhibition of cyclo-oxygenase enzyme (COX) involved in synthesis of prostaglandins. Decrease of prostaglandins can lead to decrease in pain and inflammation as they are one of the mediators involved in inflammation This enzyme exists in 2 isoforms - COX 1 and COX 2. The former is the constitutively expressed form of the enzyme, involved in prostaglandin synthesis in gastrointestinal, renal sy...