Study finds Avandia may increase risk of heart failure

Dec 13 2007

A popular class of drugs for treating type 2 diabetes is under scrutiny again. A new Canadian study released by the Institute for Clinical Evaluative Sciences (ICES) finds that drugs such as Avandia increase the risk of heart failure, heart attacks and death.

Published in the December 12th issue of JAMA, ICES scientists looked at the glitazone class of drugs including rosiglitazone (Avandia) and pioglitazone (Actos) in the first real world population-based study of its kind. All Ontario residents aged 65 years or older, treated with at least one oral diabetic medication were followed between 2002 and 2006. "The necessity for evaluating diabetes drug outcomes in older patients is reinforced by the fact that seniors have the highest prevalence of diabetes and represent over 40% of the population with the disease," says lead author and ICES researcher, Dr. Lorraine Lipscombe. "We cannot be certain whether similar effects would be seen in younger patients. Our study represents a concern for older patients taking these drugs who are at higher risk for adverse cardiac outcomes."

Published in the December 12th issue of JAMA, ICES scientists looked at the glitazone class of drugs including rosiglitazone (Avandia) and pioglitazone (Actos) in the first real world population-based study of its kind. All Ontario residents aged 65 years or older, treated with at least one oral diabetic medication were followed between 2002 and 2006. "The necessity for evaluating diabetes drug outcomes in older patients is reinforced by the fact that seniors have the highest prevalence of diabetes and represent over 40% of the population with the disease," says lead author and ICES researcher, Dr. Lorraine Lipscombe. "We cannot be certain whether similar effects would be seen in younger patients. Our study represents a concern for older patients taking these drugs who are at higher risk for adverse cardiac outcomes."

The ICES study explored three distinct outcomes using Ontario health care databases: hospital visits for congestive heart failure, hospital visits for heart attacks and death from any cause, and looked at exposure to specific diabetes drugs in seniors. Compared to other diabetes pills glitazones (Avandia & Actos ) are associated with the following results:

- 60% relative increase in heart failure, 40% relative increase in heart attacks, 30% relative increase in death. - This translates into an estimated 3 additional episodes of heart failure, 4 additional heart-attacks and 5 additional deaths for every 100 individuals taking these drugs, over a 4 year period in a high- risk older population. - Risk predominantly among those taking rosiglitazone (Avandia). - Smaller numbers of people received the other drug pioglitazone (Actos), limiting our ability to be certain about adverse events in this group.

Co-author and Senior ICES Scientist, Dr. David Alter says, "We don't want people to panic. Treatment decisions must remain individualized with doctors and patients weighing the potential harms and benefits of these drugs, especially when used among the elderly who are at higher-risk of cardiac complications."

The Ontario based ICES study comes on the heels of the Food and Drug Administration (FDA) slapping a prominent black box label warning on the popular diabetes drug Avandia telling patients that it may, or may not, increase the risk of heart attacks. It is the most severe type of warning the agency can require pending further research. Glaxo Smith Kline, Avandia's manufacturer has agreed to do a longer term study comparing the drug to other medications, but those results won't be available for another six years. Since the drug's approval in 1999, more than 7 million people worldwide have taken Avandia, designed to increase the body's sensitivity to insulin, generating sales worth $3 billion annually.

"Our study demonstrates the importance of post-marketing surveillance of new drugs. Manufacturers are often required to only demonstrate diabetes medications lower blood sugar not that they prevent long term consequences of diabetes. Research trials are often insufficient to detect less common adverse effects of drugs, so ongoing safety monitoring of drug side effects in larger real-world populations is vital. Experts from regulatory bodies such as Health Canada and the Food and Drug Administration will have to consider our findings in the context of all the evidence so far, to decide the future of these drugs," says Dr. Lipscombe.

The study 'Thiazolidinediones and Cardiovascular Outcomes in Older Patients with Diabetes' is in the December issue of JAMA.