Acetaminophen has been around for over a century and is the most widely used drug compound in the world. In the U.S., acetaminophen (also called paracetamol or APAP) is present as an active ingredient in over 600 prescription and over-the-counter medications marketed to relieve pain or reduce fever, including Tylenol. Every week, nearly one in four Americans takes an acetaminophen-containing medication, and pediatricians routinely recommend acetaminophen as the treatment of choice for fever in children.