Acetaminophen In the late 1800’s it was discovered that papa-amino-phenol, could reduce fever, but the drug was too toxic to use. A less toxic extract called phenacetin was later found to be just as effective but also had pain-relieving properties. In 1949, it was learned that phenacetin was metabolized into an active but also less toxic drug, acetaminophen. Since then, acetaminophen has been sold under many over the counter brand names, most popular being Tylenol. Acetaminophen serves one basic purpose, to relieve pain. It is the main ingredient in pain killers that relieve headaches. It also substitutes anesthesia in circumcision surgery because anesthesia often cann