Drug Is Seen to Limit Progression to Diabetes

People at high risk of developing diabetes may be able to ward off the disease by taking the drug pioglitazone, a new study suggests, but critics say the potential side effects of the medication may outweigh the benefits for those who are still disease-free.

Pioglitazone, sold under the brand name Actos, belongs to the same class of drugs as the diabetes medication rosiglitazone, sold as Avandia, which was found to increase the risk of heart attack in patients taking it. Rosiglitazone was taken off the market in Europe, and its use is greatly restricted in the United States.

Pioglitazone is believed to be safer than rosiglitazone, but it has been linked to an increased risk of congestive heart failure, and the Food and Drug Administration is investigating a possible link to bladder cancer.

In the new study, a team led by researchers at the University of Texas Health Science Center in San Antonio followed patients who had elevated blood sugar levels but had not yet progressed to diabetes, tracking them for just over two years on average. Those who took pioglitazone daily were significantly less likely to develop the disease than a similar group given a placebo, the team found.

The annual average incidence of progression to diabetes was 7.6 percent for the placebo group and 2.1 percent for those taking pioglitazone, representing a 72 percent reduction in risk, the researchers said.

Dr. Ralph A. DeFronzo, chief of the diabetes division at the health science center and senior author of the study, called the results “astounding.”

Patients taking the drug gained weight, however, and experienced fluid retention. Critics said it was not clear whether the drug prevented diabetes or simply lowered elevated blood sugar, and some suggested that a better alternative would be for people at risk to exercise and eat a healthier diet.

“The F.D.A. has never approved any drug to prevent diabetes,” said Dr. Steven Nissen, chairman of cardiovascular medicine at the Cleveland Clinic, who first raised questions about the safety of rosiglitazone. “There’s a reason for skepticism, because we don’t know whether these drugs are really preventing diabetes or just masking it.”

The study was published on Thursday in The New England Journal of Medicine. It was financed in part by Takeda Pharmaceuticals, maker of pioglitazone.