Long Acetaminophen Use Linked to Kidney Damage : Health: The painkiller is sold mostly under the Tylenol label. Researchers note it is safe and useful in most cases.
The painkiller acetaminophen can severely damage kidneys if it is taken for long periods, according to a new study that reinforces previous fears about the popular drug.
Acetaminophen, most commonly known by the trade name Tylenol, causes an estimated 10% of the 50,000 cases of kidney failure that occur in the United States each year, the researchers report today in the New England Journal of Medicine. Preventing those cases could save the country $700 million a year in health expenses, according to government figures.
An average daily dose of more than one tablet can double the risk of kidney failure, as can the use of more than 1,000 tablets over an extended period, according to researchers from the Johns Hopkins School of Public Health in Baltimore.
The report comes only a day after a separate team reported that taking the drug during a fast, either voluntary or caused by illness, can cause serious liver damage.
The two reports represent a major dilemma for the millions of people who require frequent pain relief and who have switched from aspirin to acetaminophen because it was thought to be safer.
But Dr. Paul K. Whelton, a neurologist at Johns Hopkins and senior author of the new report, cautioned that “almost every drug that has beneficial effects has some potential for side effects. We shouldn’t interpret these results as saying that acetaminophen is dangerous. It has a long track record of safety and is a very useful drug. There is no guarantee that another drug will be safer or better.”
No one should stop using acetaminophen as a result of the two studies, Whelton concluded, although people should certainly be switched away from it at the first sign of kidney problems. Rather, he said, they provide a strong argument that “we should not just take pills without a good reason.”
Tylenol maker Johnson & Johnson of New Brunswick, N.J., immediately responded to today’s study. “Independent medical experts who have reviewed the article are unmoved by its arguments and have serious concerns about the survey methods used, the analysis of the data generated and the conclusions drawn by the authors,” said a statement released by the company.
“We are very concerned this report will unnecessarily alarm the public, scaring people into switching from acetaminophen to other pain relievers that carry greater risks with everyday use,” the statement continued.
According to the National Headache Foundation, as many as 45 million Americans suffer chronic headaches and may use painkillers regularly. Nearly 32 million suffer arthritis severe enough to require medical care, and most of them also use painkillers.
Until the 1970s, those painkillers were almost always aspirin. But physicians eventually began switching their patients to other painkillers because of a variety of concerns about aspirin, ranging from allergic reactions to gastrointestinal bleeding.
The replacement of choice was acetaminophen, which is sold under the brand names Tylenol, Anacin-3, Panadol and Datril. Those brands account for 48% of the annual $2.9-billion over-the-counter sales of pain relievers in this country, according to the consulting firm Kline & Co. Aspirin now accounts for less than one-third of the market.
For the new study, Whelton and his colleagues identified everyone in the District of Columbia, Maryland, Virginia and West Virginia who began kidney dialysis between January and July, 1991. The 716 patients they identified were compared to a control group of 361 other people who were selected by randomly dialing the telephone in the same areas. Both groups were then questioned extensively about their use of aspirin, acetaminophen and other so-called non-steroidal anti-inflammatory agents (NSAIDs), including ibuprofen, naproxen and indomethacin.
They found that the risk of kidney failure was about 1.4 times normal for individuals who took two to seven acetaminophen tablets per week, rising to 2.1 times normal for those who took more than a tablet per day. For individuals who took more than 5,000 acetaminophen tablets over their lifetimes, the risk was 2.4 times higher.
No increase in risk was observed for people who took aspirin. For those who took more than 5,000 tablets of other NSAIDs, the risk was 8.8 times normal. But Whelton cautioned that the number of individuals who took such high doses of NSAIDs was small, so the team was less confident in that result.
The results largely confirm findings of a 1989 study by researchers at the National Institute of Environmental Health Sciences. That study had been highly criticized for its design, however, and Whelton and his colleagues believe theirs is less subject to dispute.
Nonetheless, a spokesman for Johnson & Johnson pointed out that most of the patients with kidney failure from other causes had probably switched from aspirin to acetaminophen at their doctors’ orders when their kidney damage first became apparent. Such switching, the company said, would have biased the results against acetaminophen because the patients would have been more likely to recall their use of that drug.
In a report Wednesday in the Journal of the American Medical Assn., researchers at the University of Pittsburgh reported that eight individuals who had been too sick to eat and who then took as many as 20 extra-strength tablets of acetaminophen within 24 hours developed severe liver damage.
The researchers speculated that fasting altered the body’s metabolism of acetaminophen, leading to a byproduct toxic to the liver. Such an alteration, accompanied by liver damage, is already known to occur in patients who consume acetaminophen while highly intoxicated. Warnings against such use now appear on some packages.
