Prostaglandins are compose of 2 enzymes namely cyclooxygenase 1 and cycloxygenase 2. Cox 2 inhibitors are NSAIDS yet selectively blocks only Cox 2 enzyme and not the Cox 1. This will then disrupt the prostaglandin production by Cox 2 that causes the pain or swelling. They differ from other NSAIDS as it only blocks Cox 2 compared to other NSAIDS blocking both enzymes.