The cyclooxygenase (COX) enzyme has two forms: COX-1 and COX-2. COX-1 is found in a lot of cells all the time, notably the lining of the stomach where it regulates acid production. COX-2 is not present in most cells normally, only appearing when things are going wrong. As a result, COX-2 was thought to be responsible for the bad effects of the COX enzyme-pain and inflammation. Vioxx was developed based on this belief that COX-2 was responsible for the bad effects of the COX enzyme and to reduce or even eliminate the gastrointestinal risks involved with the non-selective (traditional) NSAIDs like Aspirin (acetylsalicylic acid, ASA), Ibuprofen, Nabumetone and Naproxen, that inhibit both COX-1 and COX-2 enzymes. However, COX-2 serves other purposes besides its role in inflammation. Among the purposes the COX-2 enzyme serves is that it plays a major role in controlling the cardiovascular system-stopping platelets from forming blood clots (thrombi – plural form of thrombus) in the heart, and preventing damage to vessels. It also serves other functions that are beyond the scope of this FAQ section to explain.