Taking too much Tylenol or acetaminophen over several days can have dangerous side effects and may even cause a fatal overdose, according to a recent study. Over 50 million people in the U.S. use acetaminophen each week to treat a variety of ailments, including acute and chronic pain and for the reduction of fever.
The study, which was published in the British Journal of Clinical Pharmacology, looked at “staggered overdoses” in which a person regularly exceeded the daily recommendation of acetaminophen, the active ingredient in Tylenol. In the study, staggered small overdoses of acetaminophen were even more deadly than a single, large overdose.
“They haven’t taken the sort of single-moment, one-off massive overdoses taken by people who try to commit suicide, but over time the damage builds up, and the effect can be fatal,” said researcher Kenneth Simpson of the University of Edinburgh in Scotland.
Dr. Simpson and researchers at the university and the Scottish Liver Transplantation Unit studied 663 patients at the Royal Infirmary of Edinburgh who suffered liver injuries caused by acetaminophen. 161 of the patients, or nearly one in four, had taken a staggered overdose, mostly to relieve common pain.
“On admission, these staggered overdose patients were more likely to have liver and brain problems, require kidney dialysis or help with breathing and were at a greater risk of dying than people who had taken single overdoses,” said Simpson.
Complicating the issue further is that staggered overdose patients often don’t report the overdose, only that they are feeling unwell, so the overdose may not be diagnosed right away. Doctors usually assess overdose patients by taking blood samples. In the case of a large, single overdose, the blood sample provides valuable information about the patient. But in the case of staggered overdose, the blood test may reveal low levels of acetaminophen – even though the patient is at greater risk of liver failure and death.
The study found that 37% of the staggered overdose patients died, while 27% of the single overdose patients passed away.
Simpson says people taking acetaminophen should stay within the recommended daily limit and take even less of it if they are on other pain killers.
In a statement to the American News Journal, McNeil Consumer Healthcare, the Johnson & Johnson company that makes Tylenol, said there were several limits to the study, including the reliability and validity of patient recall.
“Hundreds of studies have demonstrated that acetaminophen, when used as directed, is safe and well tolerated,” the statement said. “When patients either intentionally or unintentionally take more than the recommended maximum daily dose, acetaminophen can cause liver injury.”
In July, McNeil Consumer Healthcare lowered the recommended daily dose of Tylenol from 4,000 mg per day to 3,000 mg per day. For consumers taking Extra Strength Tylenol 500 mg tablets, that means taking a maximum of 6 tablets per day instead of 8 per day. The company said it lowered the recommended dose to reduce the risk of accidental overdose.
Acetaminophen can be found in hundreds of over-the-counter and prescription drugs, including Vicodin, Percocet, NyQuil, and Tylenol. Acetaminophen overdose is the leading cause of acute liver failure in the U.S., with thousands of hospitalizations and hundreds of deaths each year.