(Chem. & Med.) A chemical substance (C17H14O4S, molecular weight 314.36) used in medicine as an analgesic to alleviate pain and inflammation; it is a synthetic compound, and is marketed by Merck & Co. under the trade name Vioxx, in tablets giving dosages of 12.5 or 25 milligrams. It is classed as a non-steroidal anti-inflammatory drug (NSAID). Chemically, it is 4-[ 4-(methylsulfony)phenyl ]-3-phenyl-2(5H) furanone. Its chemical structure contains two phenyl rings and a furanone ring. It is believed to act by inhibition of prostaglandin biosynthesis, through inhibition of the enzyme cyclooxygenase-2 (COX-2); unlike aspirin, it does not inhibit cyclooxygenase-1. [ PJC ]