Expert Warns of Overuse of Over-the-Counter Pain Medication

Acetaminophen is generally a safe and effective medication, one that is used by millions of people every day to treat minor aches and pains and to diminish fevers. It might surprise many people, then, that overdoses of Tylenol and other products containing acetaminophen account for a staggering 40 percent to 50 percent of all acute liver failure cases each year in the United States.

Of those cases, nearly half are unintentional overdoses, a recent finding that many experts say is alarming. That's why people need to take extra care not to take even a little more of the medication than the recommended dose during any 24-hour period.

"My overall recommendation for people using Tylenol is that it is a safe drug," says Robert J. Fontana, M.D., associate professor of internal medicine at the University of Michigan Medical School, member of the Gastroenterology Division and medical director of liver transplantation. "However, like most other things in life, too much of a good thing can be bad for you."

For instance, an adult should not take more than eight Tylenol Extra Strength pills, which contains 500 milligrams per tablet, in a 24-hour period (i.e. the maximum daily dose is 4,000 milligrams per day). Exceeding that dosage, could lead to inadvertent liver or kidney damage in some people, Fontana says.

Fontana notes that damage occurs acutely rather than chronically - in other words, it isn't the dosage of the medicine a person takes over several weeks that is the problem, it is the daily dose that may lead to liver toxicity.

Here's how the problem occurs: Whenever you take a medication, your liver typically is involved with metabolizing, or eliminating, the drug from your system. When you take too much acetaminophen, you overwhelm your body's ability to eliminate the medication safely. High levels of the medication can build up in the blood, and that can damage liver cells that are trying to metabolize the drug, which can lead to liver injury, Fontana says.

A multicenter study that the U-M Health System recently participated in indicated that about half of acetaminophen overdoses that resulted in liver failure were unintentional, something the researchers refer to as "therapeutic misadventures."

"What I mean by that is that individuals were taking acetaminophen for some type of medical problem - such as a headache, back pain or the flu - inadvertently took too much and subsequently developed liver failure," Fontana says. "If you go to a drug store, as many as 150 products that consumers can buy without a prescription have acetaminophen in them."

It doesn't take much for someone to consume a toxic dose of acetaminophen. For instance, consider someone who is taking an over-the-counter product that helps stop sneezing or coughing that contains 350 to 500 milligrams of acetaminophen per dose, with one or two doses every four hours. If that person also has a headache or muscle aches, he or she may take some acetaminophen and quickly go into the potentially toxic range.