The spate of bad news about painkillers has dealt a major setback to what had been a highly promising effort to use the drugs to prevent a host of leading killers, including many...

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WASHINGTON — The spate of bad news about painkillers has dealt a major setback to what had been a highly promising effort to use the drugs to prevent a host of leading killers, including many types of cancer, Alzheimer’s and other forms of dementia.

Since concerns emerged that drugs such as Vioxx and Celebrex might cause heart attacks and strokes, researchers testing the drugs in dozens of studies have been frantically scouring whatever data they have gathered for signs of danger, urgently debating whether the trials should continue, and quickly informing participants of possible risks.

Several large studies have shut down fully or partially, including trials for preventing colon cancer, prostate cancer, Alzheimer’s and, just last week, two large international studies evaluating Celebrex to cut the risk of getting breast cancer or suffering a recurrence. Other studies have been temporarily suspended.

Overall, the startling new concerns about the drugs’ safety have cast a pall over what had been one of the most exciting fields of biomedical research: trying to gain new insights into the underlying cause of a wide spectrum of illnesses.

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“It’s definitely been a big setback,” said Dr. Raymond DuBois of Vanderbilt University School of Medicine in Nashville, Tenn. “It’s really disappointing, because there had been a lot of enthusiasm in this area, and a lot of trials were under way. I think this is going to slow things down considerably. It’s really unfortunate.”

The developments are particularly distressing because a large body of evidence indicates the drugs could provide significant benefits aside from relieving pain. Even the studies that revealed the possible heart-attack and stroke risks produced evidence that the approach could be highly effective for reducing the risk of cancer.

“We have produced evidence for the proof-of-principle that agents like these could be effective for preventing cancer,” said Dr. Robert Bresalier of the University of Texas M.D. Anderson Cancer Center in Houston, who led the study that raised the first alarm. “There’s a great deal of data suggesting that these drugs might be beneficial in terms of preventing or treating a large number of cancers. It would be a major mistake not to go forward with this line of research.”

Several researchers said they thought the response to revelations of potential risks was an overreaction. It may turn out that Celebrex and similar drugs pose less of a danger than initially suspected, or that the drugs could prove useful at lower doses or for certain patients, they said.

“I think we have created a situation of mass hysteria that’s completely unwarranted,” said Dr. Carol Fabian, director of breast-cancer prevention at the University of Kansas Medical Center in Kansas City, who decided to continue two breast-cancer studies after warning participants of the possible risk. “I don’t think we have all the data yet, and we may be prematurely drawing conclusions.”

The drugs were developed to relieve pain with fewer side effects than existing painkillers, but researchers began testing them to treat or prevent a variety of diseases because of their ability to reduce inflammation, limit cell growth, inhibit the growth of blood vessels that nourish tumors and, in the case of breast cancer, lower estrogen levels.

The alarm began in September when Merck & Co. pulled its blockbuster arthritis drug Vioxx from the market because Bresalier’s study indicated the drug doubled the risk of heart attacks and strokes. Bresalier was testing whether Vioxx reduced the risk of colon polyps, which can lead to cancer. Merck then shut down another colorectal-cancer-prevention trial, as well as one for prostate-cancer prevention.

That prompted the National Institutes of Health to begin scrutinizing other trials using similar drugs, especially Pfizer’s popular Celebrex. On Dec. 17, the NIH announced that another cancer-prevention trial had found evidence of a similarly increased risk for heart problems for Celebrex, and shut down that trial.

Although another study contradicted that finding, the announcement caused patients in many studies testing Celebrex to stop taking their drugs, including those in a large Alzheimer’s prevention trial. That trial also raised concern about the over-the-counter pain reliever naproxen, sold as Aleve.

Dr. John Breitner of the University of Washington, who led the Alzheimer’s trial, said the hint of risk for naproxen was far from clear from his data and that the main reason his trial shut down was that so many participants were worried about Celebrex.

Other Alzheimer’s researchers expressed similar disappointment, saying they feared the developments would unnecessarily derail a promising line of research.

“We should not give up on this,” said Dr. Linda Van Eldik of the Northwestern University Feinberg School of Medicine in Chicago. “Inflammation is a key player in the damage in Alzheimer’s. I would hate to have something like these initial results make people stop this whole area of research, because I think it’s really important.”

Similarly, researchers leading the two large breast-cancer trials discontinued parts involving Celebrex in part because of the health concerns, but primarily because they thought the rising alarm made it impractical to continue.

“We were concerned that, because of the widespread media attention around this class of agents, the reaction of ethics-review committees around the country, and the volume of telephone contacts we were having from study participants, that the entire machinery of our clinical-research program would unravel if we tried to persist,” said Dr. Paul Goss of the Massachusetts General Hospital in Boston, who is leading the studies.

Goss and others said that even if it turns out Celebrex and similar drugs do increase the risk of heart attacks and strokes, many patients may be willing to take that risk to cut their chances of getting cancer, especially if it runs in their families.

Other researchers agreed, saying what might emerge is a more targeted use of the drugs only for those at low risk for heart disease and high risk for other diseases.

But Dr. Elias Zerhouni, director of the National Institutes of Health, defended the NIH’s actions, saying even a hint of risk warranted discontinuing the Alzheimer’s trial because it involved healthy people. “You have to err on the side of doing no harm,” he said.