A class of diabetes drugs may greatly increase a person's chance of heart failure, says a U.S. research review.

The risk of heart failure in patients taking thiazolinediones, can be up to 100 per cent higher than in those who forgo the drugs, researchers at Wake Forest University in North Carolina have found after studying randomized trials, controlled observational studies and case reports.

Thiazolinediones led to heart disease even in patients who had no known cardiac risks, the report finds.
(CBC)

Thiazolinediones, which include medications like Avandia and Actos, are known to enhance insulin sensitivity.

The research findings will appear in the August issue of Diabetes Care.

In the research review, heart failure occurred equally at high and low doses. The medium time for the onset of heart failure was 24 weeks after beginning drug therapy. The median age of victims was 67, with 26 per cent of all cases below age 60.

"The occurrence of heart failure several months after initiation of treatment suggests a long-term effect of the drugs, which may not be avoided by beginning with low doses," said Sonal Singh, lead author of the report, in a release.

Currently, the product label for both drugs cautions patients with severe heart failure about taking the drugs. It also warns about the increased risk of heart failure if used in combination with insulin, a mainstay of diabetes treatment. 

But the report finds that heart failure can occur even if patients don't have any heart problems. For that reason, the authors call for a review of the recommendations of both the American Heart Association and the American Diabetic Association. Both groups recommend thiazolinediones to diabetics with early-stage heart failure or one or more risk factors for cardiac problems, without heart disease.

The researchers theorize that the development of heart failure may be caused by fluid retention brought on by the thiazolinediones in people who are susceptible, or in people who have latent heart disease.

On May 31, Health Canada issued an communique about Avandia, regarding its connection to an increased risk of heart attack and cardiovascular death in patients with Type 2 diabetes. Further investigation of these results is underway.

According to the Canadian Diabetes Association, two million Canadians have diabetes. Four out of five people with diabetes will die of heart disease and studies also show that people with diabetes are prone to heart disease at a much earlier age than those without diabetes.

Risk factors include high blood glucose levels, elevated blood pressure, being overweight and having high cholesterol levels.