SATURDAY, June 25, 2011 (HealthDay News) -- New research shows that older people with type 2 diabetes who take drugs known as sulfonylureas to lower their blood sugar levels may face a higher risk for heart problems than their counterparts who take metformin.
Of the more than 8,500 people aged 65 or older with type 2 diabetes who were enrolled in the trial, 12.4 percent of those given a sulfonylurea drug experienced a heart attack or other cardiovascular event, compared with 10.4 percent of those who were started on metformin.
In addition, these heart problems occurred earlier in the course of treatment among those people taking the sulfonylurea drugs, the study showed.
The head-to-head comparison trial is slated to be presented Saturday at the American Diabetes Association annual meeting in San Diego. Because the findings are being reported at a medical meeting, they should be considered preliminary until published in a peer-reviewed journal.
With type 2 diabetes, the body either does not produce enough of the hormone insulin or doesn't use the insulin it does produce properly. In either case, the insulin can't do its job, which is to deliver glucose (blood sugar) to the body's cells. As a result, glucose builds up in the blood and can wreak havoc on the body.
Metformin and sulfonylurea drugs -- the latter a class of diabetes drugs including glyburide, glipizide, chlorpropamide, tolbutamide and tolazamide -- are often among the first medications prescribed to lower blood sugar levels in people with type 2 diabetes.
The findings are important, the researchers noted, partly because sulfonylurea drugs are commonly prescribed among the elderly to lower blood glucose levels. In addition, cardiovascular disease is the leading cause of death among people with type 2 diabetes.
For several reasons, however, the new study on these medications is far from the final word on the issue, experts said.
For one, people who are started on the sulfonylureas instead of metformin are often sicker to begin with, said Dr. Spyros G. Mezitis, an endocrinologist at Lenox Hill Hospital in New York City. Metformin cannot be prescribed to people with certain kidney and heart problems, he said.
Both medications lower blood glucose levels, but go about it in entirely different ways, he explained.
"The sulfonylureas lower blood sugar by making the body produce more insulin, and this may cause low blood sugar or hypoglycemia," he said. In contrast, metformin enhances the activity of the insulin that the body produces.
Previous research has shown that metformin is not linked with as high a risk of low blood sugar as the sulfonylureas. Hypoglycemia robs the muscles -- including those in the heart -- of the glucose they need for energy, so they don't work as well.
This is why these drugs may confer a higher risk for heart attack, Mezitis said. The new study, however, is based only on observations and does not prove any cause-and-effect relationship between these drugs and heart problems.
Dr. Jerome V. Tolbert, medical director of the outreach team at the Friedman Diabetes Institute in New York City, urged caution in reacting to the new findings.
"I wouldn't bet on this study and say, 'Everyone stop taking sulfonylureas,'" he said. But, "we are using less and less of these drugs because there are now newer and better drugs out there," he added.
Some of the newer drugs are more costly, he noted. "If you are concerned about your risks, talk to your doctor for reassurance," he said, adding that people should never stop taking any prescribed medication without first talking to their doctor.
Dr. Joel Zonszein, director of Clinical Diabetes Center at Montefiore Medical Center in New York City, agreed that the latest findings are far from definitive.
But, "we are using sulfonylureas less and less now," he said. "And we are only using them in very specific patients and often for short periods of times to treat high blood sugar, and then we switch to another drug."
Find out more about type 2 diabetes at the American Diabetes Association .