The researchers say their study is the first to document a higher death rate among patients taking thiazolidinediones -- a class of diabetes drugs that includes Avandia, Actos, Avandaryl, Avandamet, and Duetact -- and that risk in their study was limited to Avandia's active ingredient, rosiglitazone.
Rosiglitazone is also an ingredient in Avandaryl and Avandamet.
But Avandia's maker says the study has "significant limitations and generates misleading conclusions" about heart attack and death.
The study appears in tomorrow's edition of The Journal of the American Medical Association.
Diabetes Drug Study
The new study included some 159,000 diabetes patients aged 66 and older in Ontario.
All of those patients took at least one oral diabetes drug between 2002 and 2005.
Using several databases, the researchers tracked death, congestive heart failure, and heart attack over about four years among patients taking thiazolidinediones or other types of diabetes drugs.
During that time, nearly 12,500 patients (about 8%) were hospitalized for congestive heart failure, a similar number had a heart attack, and more than 30,000 (19%) died of any cause.
Patients taking thiazolidinediones were 29% more likely to die, 40% more likely to have a heart attack, and 60% more likely to develop congestive heart failure than patients taking different types of diabetes drugs, according to the study.
That pattern "appeared limited to rosiglitazone" and didn't include pioglitazone, the active ingredient in Actos and Duetact, write the researchers, who included Lorraine Lipscombe, MD, MSc, of the Institute for Clinical Evaluative Sciences in Toronto.
Relatively few patients were taking Actos, so Lipscombe's team calls for further studies to see if the increased risks are limited to rosiglitazone.
"As you can see in our paper, the risk appeared limited to rosiglitazone, but there were far fewer numbers on pioglitazone so we can't exclude a similar risk with that drug as well," Lipscombe tells WebMD via email.
Diabetes Drug Warnings
In August, the FDA announced that all thiazolidinediones will get a black box warning about the risk of congestive heart failure in certain patients.
Drug Companies Respond
WebMD contacted GlaxoSmithKline, the drug company that makes Avandia, Avandaryl, and Avandamet,and Takeda Pharmaceuticals, which makes Actos and Duetact, for their comments on the study.
GlaxoSmithKline provided a written statement that argues that the Canadian study's conclusions about the risk of heart attack and death "are inconsistent with a more robust body of evidence from large, long-term, prospective, well-designed clinical studies."
"The inconsistency could be due to the fact that the Avandia patients were older, sicker, and had more chronic diseases -- and therefore higher baseline risk for [cardiovascular] events -- than patients in other medicine groups," GlaxoSmithKline spokeswoman Nancy Pekarek tells WebMD via email.
Robert Spanheimer, MD, senior director of diabetes for Takeda, tells WebMD that "we're pleased that this paper contains important information about Actos and we're pleased that data is consistent with our body of evidence showing no increase in heart attack or death with Actos."
Spanheimer says that while fewer patients in the study were taking Actos, the study's findings are consistent with "both the direction and the degree of change that we have seen in previous studies of Actos."