Tylenol (Acetaminophen) Liver Damage

  • Medical Author:
    Dennis Lee, MD

    Dr. Lee was born in Shanghai, China, and received his college and medical training in the United States. He is fluent in English and three Chinese dialects. He graduated with chemistry departmental honors from Harvey Mudd College. He was appointed president of AOA society at UCLA School of Medicine. He underwent internal medicine residency and gastroenterology fellowship training at Cedars Sinai Medical Center.

  • Medical Editor: Jay W. Marks, MD
    Jay W. Marks, MD

    Jay W. Marks, MD

    Jay W. Marks, MD, is a board-certified internist and gastroenterologist. He graduated from Yale University School of Medicine and trained in internal medicine and gastroenterology at UCLA/Cedars-Sinai Medical Center in Los Angeles.

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Why should we know that the generic name of Tylenol is acetaminophen?

For the remainder of this discussion, we will refer to the generic name acetaminophen, rather than to the brand name Tylenol. We have decided to do this to emphasize the need for people to read the labels of medicine bottles carefully. As mentioned above, the labels usually will say acetaminophen rather than Tylenol. For example, each tablespoon of the common nighttime cold remedy, NyQuil, contains 500 milligrams (mg) of acetaminophen. Similarly, each tablet of hydrocodone/acetaminophen (Vicodin), a popular, potent painkiller that contains a narcotic, has also 500, 650, or 750 mg of acetaminophen, depending on the formulation.

As already mentioned, an overdose of acetaminophen can cause liver damage. This damage occurs in a dose-related manner. (Some other medications can cause liver injury in an unpredictable fashion that is unrelated to the dose.) In other words, liver injury from acetaminophen occurs only when someone takes more than a certain amount of the drug. Likewise, the higher the dose, the greater is the likelihood of the damage. Moreover, this liver injury from an overdose of acetaminophen is a serious matter because the damage can be severe and result in liver failure and death. In fact, acetaminophen overdose is the leading cause of acute (rapid onset) liver failure in the U.S. and the United Kingdom.

Just how much acetaminophen is safe to take?

For the average healthy adult, the recommended maximum dose of acetaminophen over a 24 hour period is four grams (4000 mg) or eight extra-strength pills. (Each extra-strength pill contains 500 mg and each regular strength pill contains 325 mg.) A person who drinks more than two alcoholic beverages per day, however, should not take more than two grams of acetaminophen over 24 hours, as discussed below. For children, the dose is based on their weight and age, and explicit instructions are given in the package insert. If these guidelines for adults and children are followed, acetaminophen is safe and carries essentially no risk of liver injury.

On the other hand, a single dose of 7 to 10 grams of acetaminophen (14 to 20 extra-strength tablets) can cause liver injury in the average healthy adult. Note that this amount is about twice the recommended maximum dose for a 24 hour period. In children, a single dose of 140 mg/kg (body weight) of acetaminophen can result in liver injury. Amounts of acetaminophen as low as 3 to 4 grams in a single dose or 4 to 6 grams over 24 hours have been reported to cause severe liver injury in some people, sometimes even resulting in death. It seems that certain individuals like those who regularly drink alcohol, are more prone than others to developing acetaminophen-induced liver damage. To understand this increased susceptibility in some people, it is useful to know how acetaminophen is processed (metabolized) in the liver and how the drug causes liver injury.

Medically Reviewed by a Doctor on 5/7/2015
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