Unraveling the mysteries behind America’s No. 1 cause of acute liver failure

Twenty years ago, the federal government funded the study of a condition quietly killing hundreds of Americans a year – acute liver failure, or ALF. Growing evidence had linked ALF to overdoses of acetaminophen, the popular over-the-counter pain medication many viewed as harmless at the time.

The Acute Liver Failure Study Group’s research led to an understanding of how acetaminophen poisoning became the No. 1 cause of ALF in the United States. It’s now responsible for 46 percent of all cases and for approximately 500 deaths and 50,000 emergency room visits each year, said Dr. William M. Lee, Professor of Internal Medicine at UT Southwestern, founder of the study group, and an internationally renowned expert in liver disease.

“Acetaminophen, also sold under the brand name Tylenol and many other names, is a dose-specific toxin,” explained Dr. Lee, who holds the Meredith Mosle Chair in Liver Disease in his honor. “Taken in limited doses, it’s very safe. But acetaminophen has a narrow margin of safety compared to other pain relievers. It doesn’t take much beyond the recommended maximum daily amount to create a problem.”

Another issue is the drug’s ubiquity. Acetaminophen is the world’s most commonly used drug to treat pain and fever. It’s an ingredient in more than 500 different medicines, from cold remedies like Mucinex to pills for menstrual cramps, such as Midol, according to the website Tylenol.com. It also appears in common prescription opioid painkillers such as hydrocodone (Vicodin) and oxycodone (Percocet).

Someone with a bad cold who takes the maximum daily dose of Tylenol and then adds a Mucinex or NyQuil product containing acetaminophen would exceed the FDA’s recommended daily maximum dose of 4,000 milligrams. While this might not lead to liver failure in one day, repeating the pattern over several days is enough to result in an unintentional overdose, Dr. Lee said.