"It will be 2012 — ten years after the drug was introduced — before we know the answer," said Dr. Steven Nissen, a Cleveland Clinic cardiologist who has no role in the studies and has criticized the drugmakers over the one reported Sunday.

Dr. Robert Spiegel, chief medical officer for Schering-Plough, said the study was done "with the highest integrity" and that doctors can believe the results "because of the time we took to make sure the data are right."

"We were disappointed that it was not a very balanced panel discussion" by the heart doctors who urged their peers to focus on more established treatments.

However, Kastelein said the data were far more consistent than anticipated and ample to show that the drug simply did not work.

"A lot of us thought that there would be some glimmer of benefit," said Dr. Roger Blumenthal, a Johns Hopkins University cardiologist and spokesman for the American Heart Association.

Many doctors have prescribed Vytorin without trying older, proven medications first, as guidelines advise. The key message from the study is "don't do that," Blumenthal said.

No one should ever stop any heart drug without talking with their doctors, heart specialists stressed.

However, doctors "should be thinking twice," said Duke University cardiologist Dr. Robert Califf. He takes the drug himself because he cannot tolerate the high dose of statins he otherwise would need.

Dr. James Stein, director of preventive cardiology at the University of Wisconsin-Madison, said many doctors prescribe Zetia and Vytorin because they seem to be safe ways to get cholesterol down quickly, without annoying side effects like flushing that some other medicines carry.

Stein, who has consulted for Schering-Plough, said that after six years on the market, it would have been good to see better results on a drug so many doctors believed would help, "but the reason we do research is so we don't have to rely on our 'beliefs' — we can rely on data."

The New England Journal also published a report showing that Vytorin and Zetia's use soared in the United States amid a $200 million advertising blitz. In Canada, where marketing drugs directly to consumers is not allowed, sales were four times lower.

Merck is based in Whitehouse Station, N.J.; Schering-Plough, in Kenilworth, N.J.

In addition to the two Congressional committee probes, New York State Attorney General Andrew Cuomo subpoenaed the companies in a similar probe in January.

"While these corporations profited, Americans were left in the dark," Cuomo said in a written statement Sunday. "The millions who take this drug, taxpayers who subsidize its use through the Medicaid and Medicare programs, and Merck and Schering-Plough's investors deserve to know why it took so long for the results to be made public. This new information underscores our concerns and advances our investigation, which we will pursue aggressively."

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On the Net:

New England Journal: www.nejm.org

Cardiology conference: www.acc.org