New study implicates Tylenol

The highest recommended dose caused problems.
LOS ANGELES TIMES
The highest recommended dose of Extra Strength Tylenol sharply increased liver enzymes in healthy adults in a clinical study, an early sign of possible organ damage.
Although overdoses of Tylenol can harm the liver, the study published today in the Journal of the American Medical Association is the first to spot hints of trouble in healthy people taking the pain reliever as directed.
"This study shows that even taking the amount on the package can be a problem for some people," said Dr. William M. Lee of University of Texas Southwestern Medical School, who was not involved in the research.
Tylenol is the leading brand of acetaminophen, which is found in more than 200 types of pain relievers and cold remedies. An estimated 100 million Americans take acetaminophen safely each year.
The over-the-counter drug is the leading cause of acute liver failure in the United States. Some researchers want more regulation to prevent overdoses. In England, concerns about suicide through acetaminophen overdose led to restrictions on how many pills could be sold at one time.
Lee said the latest study showed that the maximum dose of Extra Strength Tylenol was too high. The maximum dose is 4 grams daily, or two 500 milligram pills every six hours.
Dr. Paul Watkins of the University of North Carolina, Chapel Hill, the study's lead author, said he thought acetaminophen was safe at the highest doses, but the margin of safety was small.
Study procedures
The study of 145 healthy volunteers at two U.S. medical centers compared a placebo pill with Extra Strength Tylenol and prescription painkillers that contain acetaminophen, such as Percocet, which is a combination of acetaminophen and oxycodone, an opioid painkiller.
Patients took the medication or placebo every six hours for 14 days. Aminotransferase, a liver enzyme that when found at elevated levels can indicate possible liver damage, was measured daily for eight days and at regular intervals after that. All patients were on the same diet.
Out of 106 patients, 41, or 39 percent, taking acetaminophen alone or in combination with another drug saw their liver enzymes increase to more than three times the upper limit of normal, scientists said. Twenty-seven patients had enzyme levels exceeding five times normal, and eight patients had eight times the normal amount of enzyme.
Three times the normal level of aminotransferase is considered the threshold where doctors become concerned about possible liver damage.