BOSTON — A study concludes heavy use of Tylenol and other brands of acetaminophen may cause about 5,000 cases of kidney failure each year. Researchers also recently reported that moderate overdoses can damage the liver.

The latest of the studies, published in Thursday’s issue of the New England Journal of Medicine, found that averaging just one pill a day for at least a year may double the risk of kidney failure.

Despite the apparent hazard, however, researchers noted that both kidney and liver damage are rare, even for heavy users. For most people who take a pill or two occasionally for a headache, the medicine appears safe.

Nevertheless, the researchers estimate that eliminating heavy use of acetaminophen could prevent 10 percent of all cases of kidney failure, a life-threatening condition requiring kidney dialysis. Preventing these acetaminophen-related cases would reduce the nation’s medical bills by about $700 million annually.

Last year, acetaminophen accounted for 48 percent of the nation’s $2.9 billion over-the-counter pain reliever sales, according to Kline & Co., a consulting firm. Tylenol made up about 70 percent of acetaminophen sales.

Johnson & Johnson, the parent of Tylenol maker McNeil Consumer Products Co., attacked the latest study.

“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 company said.

About 50,000 new cases of kidney failure are diagnosed in the United States annually, and about 190,000 people are being treated for the condition.

The senior author of the kidney report, Dr. Paul K. Whelton of Johns Hopkins School of Public Health, said the researchers are most worried about those who take acetaminophen steadily for a long time.

“We are really talking about care and caution, not just popping pills at the slighest ache and pain,” he said.

The study was based on a survey of 716 people on kidney dialysis. Interviewers compared their pill-taking histories with those of 361 healthy people.

Among the findings:

The risk of kidney failure increased about 40 percent in those who took acetaminophen between twice a week and once a day for at least a year, compared with those who used the drug less often.

The risk was double in people who used the pain reliever an average of once or more a day for at least a year.

Aspirin does not appear to harm the kidneys.

Nonsteroidal anti-inflammatory drugs also were linked with kidney damage, although the relationship was less clear than with acetaminophen. The doctors looked at two over-the-counter varieties, ibuprofen and naproxen, as well as indomethacin, which is sold by prescription.

Johnson & Johnson said that people in early stages of kidney disease are urged to take only acetaminophen for pain relief and that this could account for the high use of the medicine among victims of kidney failure.

However, Dr. Michael J. Klag, another co-author of the study, said this was unlikely to explain the study’s results, in part because the researchers found high lifetime use of acetaminophen among those who later developed kidney disease.

At least two other studies in the past five years have suggested a link between acetaminophen and kidney disease.

Dr. William Henrich of the University of Texas Southwestern Medical School noted that despite these earlier reports, acetaminophen is still many doctors’ first choice for pain relief.

“Heretofore we have regarded acetaminophen as relatively benign,” Henrich said. “This paper would suggest acetaminophen needs to be regarded more cautiously.”

The researchers said the risk of heavy acetaminophen use may be worth taking for some people, such as those with arthritis who need large amounts to control symptoms.

They also note that while aspirin does not appear to harm the kidneys, it carries other side effects, such as an increased risk of bleeding in people with ulcers.

Associated Press

Over-the-counter pain relievers and their pros and cons:

Acetaminophen

Brand names: Tylenol, Datril.

Advantages: Relieves pain and fever. Does not irritate stomach.

Disadvantages: Heavy or prolonged use may damage liver and kidneys.

Aspirin

Brand names: Bufferin, Anacin.

Advantages: Relieves pain, fever, inflammation. Prevents heart attacks.

Disadvantages: Inteferes with blood clotting. May trigger stomach bleeding. May cause Reye’s syndrome in children with viral infections.

Ibuprofen

Brand names: Advil, Nuprin.

Advantages: Relieves pain, fever, inflammation.

Disadvantages: Interferes with clotting. May cause stomach bleeding, ulcers and irritation. Heavy or prolonged use may damage liver and kidneys.

Naproxen

Brand names: Aleve.

Advantages: Relieves pain and fever. One dose lasts 8-12 hours.

Disadvantages: May cause stomach bleeding, ulcers and irritation. Prolonged use may harm kidneys.