If a medication does its job safely, regulators may approve it even if nobody knows how it works. That's been the case for acetaminophen, commonly sold as Tylenol.
A team of scientists at Brigham Young University in Provo, Utah, is now a step closer to unraveling this medical mystery. The researchers report that acetaminophen targets a previously unidentified enzyme, which they call cyclooxygenase-3, or COX-3.
Two COX enzymes identified in the early 1990s transform arachidonic acid into prostaglandins, which are natural substances that can induce pain and inflammation. Acetaminophen's over-the-counter competitors–aspirin and ibuprofen–stop inflammation by binding to COX-1 and COX-2 and short-circuiting the prostaglandin-making pathway. Newer prescription drugs, celecoxib and rofecoxib, target COX-2 only. These three nonsteroidal anti-inflammatory drugs reduce pain and fever.