Celebrex (celecoxib) drug molecule. Celecoxib is a COX-2 inhibitor, a class of non-steroidal anti- inflammatory drug used as a painkiller. It belongs to the same class of drugs as Vioxx (rofecoxib), which was withdrawn in 2004 over fears that it may increase the risk of heart attack or stroke. In August 2005, the manufacturers of Vioxx, Merck & Co, were ordered to pay ?141m to the widow of a man who died of a heart attack while taking Vioxx. The finding opens the floodgates for similar claims by thousands of others. In early 2005, the packaging of Celebrex was altered to include a prominent warning of the risks associated with COX-2 inhibitors. In this molecule, carbon is grey, nitrogen blue, oxygen red, sulphur yellow, fluorine green, and hydrogen small and grey.