Acetaminophen is a pain-relief medicine used to treat headaches, muscle aches, arthritis, colds and fevers. It is the active ingredient in Tylenol and many other products, including some cold medicines. As of 2015, acetaminophen is the most widely used fever- and pain-relief medicine in the United States, notes WebMD.
Acetaminophen is a safe and effective medicine to reduce fevers and relieve mild-to-moderate pain, including backaches, sprains and menstrual cramps, according to WebMD. Acetaminophen does not have the same negative side effects as other pain relievers, such as stomach upset or heart problems.
Acetaminophen does have negative side effects if not taken properly, notes WebMD. It can cause liver damage, and the risk increases if more than three alcoholic drinks a day are consumed. Anyone with liver disease is urged to consult a doctor before taking acetaminophen. Taking more than the recommended dose or taking additional drugs containing acetaminophen can also cause liver damage.
Signs of liver damage from acetaminophen include nausea, pain in the upper stomach, loss of appetite, dark urine or jaundice, notes Drugs.com. Call a doctor immediately if the symptoms appear. Acetaminophen is available in pill or capsule form, as a liquid solution and in chewable tablets for children. Acetaminophen is not recommended for nursing mothers because the drug can pass into breast milk and may harm a nursing baby.