Poisonings From Tylenol and Acetaminophen Are Rising

"It's extremely frustrating to see people come into the hospital who felt fine several days ago, but now need a new liver," said Dr. Tim Davern, one of the authors and a gastroenterologist with the liver transplant program of the University of California at San Francisco. "Most had no idea that what they were taking could have that sort of effect."

"I see some young women who have been suffering flulike symptoms for the better part of a week, and not eating much," Dr. Davern said. "They start with Tylenol, and maybe add an over-the-counter flu medicine on top of that, and pretty soon they've been taking maybe six grams of acetaminophen a day for a number of days. In rare cases that can be enough to throw them into liver failure."

Experts agree that a vast majority of people can safely take the four-gram daily maximum that labels recommend for adults - the equivalent of eight Extra Strength Tylenol spread across 24 hours - and some people swallow much more without harm.

By eight grams in a single day, a significant number of people whose livers have been stressed by a virus, medication, alcohol or other factors would run into serious trouble, Dr. Lee said. Without intervention, about half the people who swallowed a single dose of 12 to 15 grams could die.