Older diabetics taking Avandia may face higher risk of heart failure and death than those taking Actos, another drug in the same class called thiazolidinediones, according to a study released Monday by Harvard University researchers. Both drugs are used to lower blood sugar in patients with type 2 diabetes.

In November 2007, Avandia received a black box warning due to increased risk of heart attacks in diabetes patients. The drug increases the risk of heart attack by 40 percent, doubles the risk of heart failure and bone fractures and increases the risk of anemia and vision loss from macular edema.

However, the drug continues to be prescribed because the Food and Drug Administration concluded the inherent risk of heart attack wasn’t any greater than that associated with other similar medications.

But the new study appearing in the Archives of Internal Medicine appears to contradict the FDA. The study was led by Dr. Wolfgang Winkelmayer of Brigham and Women's Hospital in Boston. He and his colleagues reported people aged 65 and older who took Avandia (rosiglitazone) had a 15 percent higher rate of death after an average of one year, and a 13 percent greater risk of heart failure compared with those taking Actos (pioglitazone).

For the study, the researchers studied Medicare claims data from 28,361 US patients older than 65 years who began taking either Avandia or Actos between 2000 and 2005. Of those studied, 14,260 began treatment with pioglitazone and 14,101 with rosiglitazone.

GlaxoSmithKline, Avandia’s manufacturer disputed the findings. Company spokesman Jeff McLaughlin said “this new study is inconsistent with evidence from randomized clinical trials and has significant limitations.” He also said the company’s long-term data suggest no increased risk of death for people taking the drug.

According to the American Diabetes Association, some 23.6 million Americans have diabetes. The number is expected to rise in the coming years as rates of obesity have reached record levels. Type 2 diabetes is closely linked to obesity.