Heavy use of Tylenol and other aspirin alternatives containing the pain reliever acetaminophen -- even as little as taking one pill a day -- might double the risk of kidney failure, a study released today concludes. The research, conducted at Johns Hopkins University and published in the latest issue of the New England Journal of Medicine, also reported that moderate doses can cause liver damage, though researchers say both kidney and liver failures remain rare. Among the findings: the risk of kidney failure jumped 40 percent for people taking acetaminophen twice a week or more, and it increased 100 percent for a daily dosage. (Aspirin, meanwhile, does not appear to harm the kidneys.) Ending heavy use of Tylenol -- which accounts for 48 percent of the nation's $2.9 billion in annual pain reliever sales -- could prevent 10 percent of kidney failure cases, saving about $700 million in medical bills a year, the study concludes. But Johnson & Johnson, parent of Tylenol's maker, lashed out, calling the drug "remarkably safe" and saying the report would "unnecessarily alarm the public"