WASHINGTON, Aug. 9 — Two small studies of the popular heartburn drugs Prilosec and Nexium found that patients who took the medicines over many years had an increased risk of sometimes fatal heart attacks and heart failure.
But officials at the Food and Drug Administration played down the heart worries, saying that other studies suggested no such risks. The F.D.A. will need another three months to complete a thorough analysis of the drugs’ safety, the officials said in an announcement on Thursday.
In the meantime, doctors and patients should continue to prescribe and use the drugs as before, the officials said.
AstraZeneca, the maker of Prilosec and Nexium, released a statement saying that it agreed with the F.D.A.’s preliminary assessment. “Therefore, patients should not change their medication in the light of the study data,” the company said.
The F.D.A.’s preliminary message is part of a new agency strategy to be far more forthcoming about possible public health risks, even ones agency officials largely dismiss.
The agency came under criticism in recent months for failing for more than a year to alert the public to studies that suggested that Avandia, a medicine prescribed for Type 2 diabetes, may increase the risks of heart attacks and angina.
Agency officials initially dismissed concerns about Avandia’s safety, but a panel of experts voted overwhelmingly on July 30 that the risks were real.
“It’s hard to know if this will play out similarly until we have completed our analyses” of Prilosec and Nexium, said Dr. Paul Seligman, the agency’s associate center director for safety policy and communication.
Concerns about Prilosec and Nexium began on May 29 when AstraZeneca sent the F.D.A. the results of a 14-year study of the treatment of reflux disease that compared patients taking Prilosec with those who underwent surgery.
Within a year of the study’s inception, patients taking Prilosec were more likely to have heart attacks, heart failure and heart-related sudden death than were those who underwent surgery. The effect continued throughout the study, the drug agency said.
A second, continuing study of Nexium found similar risks early in the trial, but this effect seemed to go away as the trial continued, the agency said.
The Prilosec study suffered from several weaknesses that could have led to a false suggestion of a risk, the agency said. Patients who underwent surgery tended to be younger and healthier than those who took Prilosec. And 14 other Prilosec studies found no heart risks, it said.
“Based on everything we know now, F.D.A.’s preliminary conclusion is that the observed difference in risk of heart attacks and other heart-related problems seen in early analyses of the two small long-term studies is not a true effect,” the agency said in a written statement.
The parallels with the Avandia situation are striking, demonstrating the difficulty of trying to assess drug safety issues.
In the case of Avandia, a combined analysis of more than three dozen short-term studies revealed a heart risk, but the drug agency largely dismissed this result when a continuing long-term trial did not find such a risk. With Prilosec, a long-term trial suggested a heart risk, but the agency dismissed the finding because 14 briefer studies were more reassuring.
Prilosec and Nexium, which are nearly identical, are part of a class of medicines known as proton pump inhibitors that resolve heartburn by reducing the stomach’s production of acid. Among the other drugs in this class are Prevacid, Protonix and Aciphex.
The F.D.A. has asked for safety data from the makers of all proton pump inhibitors. Dr. Seligman said.
The agency’s announcement about Prilosec and Nexium was the earliest public warning that it had ever made during a safety review, Dr. Seligman said.
“We were cognizant from the earliest submission about whether and how we should say something,” Dr. Seligman said.
