The danger behind this common med

Days later, she was so disoriented she could not remember how many pills she had taken, and her liver was failing because she had overdosed on acetaminophen, the active ingredient in Tylenol. In pain and near death, Sullivan was taken to Massachusetts General Hospital and put on the liver transplant list. Her mother and sister flew in from the West Coast, fearing she would not live.

“So many people take Tylenol for nothing, just because they have a headache or whatever - nobody thinks it could hurt them,’’ said Sullivan, a 33-year-old resident of Dover, N.H., who has recovered but still has tests of her liver function once a month. “If somebody told me they overdosed on Tylenol, I’d laugh if it hadn’t happened to me. It’s almost like Americana.’’

Sullivan’s scare sheds a light on an issue that has recently caught the attention of federal regulators: the potential for acetaminophen, the active ingredient in Tylenol and an often-overlooked component of drugs that range from Vicodin to some formulations of NyQuil, to have toxic effects on the liver if too much is taken.

Acetaminophen is safe and effective when taken as directed. What concerns medical professionals is that the commonly used drug can - unbeknownst to many of the people who take it and may think of it casually - have severe effects if misused.

According to numbers collected by the American Association of Poison Control Centers, 348, or nearly a third of the poison-related deaths in 2007 involved acetaminophen - 208 from acetaminophen in combination with another drug, and 140 from acetaminophen alone. Poison Control centers also reported 34,953 calls involving acetaminophen in combination with another drug, and 57,325 calls regarding acetaminophen in 2007.

About half of acetaminophen overdoses are intentional, because they are an accessible way to commit suicide; but that means about half arise because people inadvertently take too much of the drug. Acetaminophen is most familiar as Tylenol, but is also part of prescription painkillers like Percocet and Vicodin and present in over-the-counter drugs like some forms of Benadryl and Triaminic.

“Somewhere along the way, acetaminophen entered the therapeutic lexicon as safe, proven, as a completely acceptable over-the-counter drug that was free of baggage,’’ said Dr. Raymond T. Chung, chief of hepatology at Massachusetts General Hospital. “The remarkable fact is that its toxicity has always been known about . . . Somewhere along the way, a culture of permissiveness took root, and with that sort of faded away the sense of threat.’’

Given the enormous number of people who take acetaminophen each year, the liver side effect is rare, and doctors are not suggesting that people stop taking the drug. Still, some doctors - and the US Food and Drug Administration - have been scrutinizing acetaminophen because it is a leading cause of acute liver failure. Dr. William M. Lee, founding principal investigator of the Acute Liver Failure Study Group, says that there are an estimated 2,000 cases of acute liver failure each year, about 40 percent of which are due to acetaminophen overdoses. Furthermore, he said, many other people are hospitalized with serious liver injury and would not be counted in that number.

Lee said that one striking thing was that new drugs now sometimes fail in development or are rejected by regulators because of effects on the liver. He cited Exanta, an anticoagulant developed by AstraZeneca, that never made it onto the market because of a potential risk of severe liver injury. Meanwhile, acetaminophen’s potential toxic effects - which are entirely preventable - are not clear to all consumers.

The scenarios, he said, often include someone who is taking medication for chronic pain and may also be using alcohol or have an underlying liver problem, or not be eating well. But it also can be as simple as a patient being told to take two painkillers every four hours following surgery, regularly taking three because of intense pain.

“That’s kind of getting up to the area where if other things weren’t in place - like you weren’t eating well - that you could certainly develop toxicity,’’ Lee said. “It’s just tragic to see someone die after bunion surgery.’’

This spring, the FDA issued a rule that labels for over-the-counter pain relievers and fever reducers include warnings about safety risks, such as liver damage. Then this summer, the FDA sought the advice of a joint advisory committee on what changes, if any, need to be made. In a two-day meeting, advisory committee members narrowly voted to recommend eliminating combination prescription products that contain acetaminophen. They also advised lowering the recommended maximum total daily dose of acetaminophen from its current four grams per day, and voted to recommend reducing the maximum single adult nonprescription dose. The FDA has not yet acted on the recommendations.

“It’s not been made clear enough to consumers that you can get acetaminophen from many different places,’’ said Dr. Peter Lurie, deputy director of the Health Research Group at Public Citizen, a consumer advocacy organization, who said the recommendations were a step in the right direction.

However, some doctors expressed concern that patients would stop taking the drug altogether, even though the side effect is a result of misusing the drug - and switching to another drug could have negative side effects. Non-steroidal anti-inflammatory drugs such as ibuprofen carry a risk of gastrointestinal bleeding. The Consumer Healthcare Products Association, a trade group for companies that manufacture over-the-counter medicines, critiqued some of the recommendations, and emphasized the safety of acetaminophen when used as directed.

Dr. Dennis Dimitri, president of the Massachusetts Academy of Family Physicians, said that most physicians do not encounter patients who suffer from misusing acetaminophen, and said he had mixed feelings about the recommendations. What the debate about acetaminophen correctly highlights, he said, is a point that has been missing from the discussion of using any medication: Precautions should be taken.

“I think there’s a false impression on the part of many people that because something is available without a prescription, that must mean it’s perfectly safe,’’ Dimitri said. “The fact of the matter is any medication you take, whether it be a prescription drug, an over-the-counter drug, an herbal supplement or vitamin, or other medication has some potential for causing problems.’’

That point hits home with Sullivan, who said she has gone over all the drugs that she takes now to be alert for potential interactions.

“It’s so not a drug when you think about it, and that’s how most people look at it,’’ she said. “I was completely thrown.’’

Carolyn Y. Johnson can be reached at cjohnson@globe.com.