“The pharmaceutical industry ganged up and attacked, discredited the findings,” Dr. Furberg said. He eventually resigned in frustration as chairman of the study’s steering committee, the expert group that continues to oversee analysis of data from the trial. One member of that committee received more than $200,000 from Pfizer, largely in speaking fees, the year after the Allhat results were released.

There was another factor: medicine moves on. Even before Allhat was finished, and certainly since then, new drugs appeared. Others, meanwhile, became available as generics, reducing the cost advantage of the diuretics. And many doctors have shifted to using two or more drugs together, helped by pharmaceutical companies that offer combination pills containing two medicines.

So Allhat’s main query  which drug to use first  became “an outdated question that doesn’t have huge relevance to the majority of people’s clinical practices,” said Dr. John M. Flack, the chairman of medicine at Wayne State University, who was not involved in the study and has consulted for some drug makers.

Dr. Sean Tunis, a former chief medical officer for Medicare, remains an advocate for comparative-effectiveness studies. But, as Allhat showed, “they are hard to do, expensive to do and provoke a lot of political pushback,” said Dr. Tunis, who now runs the nonprofit Center for Medical Technology Policy, which tries to arrange such trials.

“There’s a lot of magical thinking,” he said, “that it will all be science and won’t be politics.”

Expensive Pills

Promising better ways to treat high blood pressure, drug companies in the 1980s introduced a variety of medications, including ones known as calcium channel blockers and ACE inhibitors.

Although there was no real evidence the newer pills were better, diuretics fell to 27 percent of hypertension prescriptions in 1992, from 56 percent in 1982. Use of the more expensive pills added an estimated $3.1 billion to the nation’s medical bill over that period.