Review: Metformin a Top Diabetes Drug

One of the many medications used to treat type 2 diabetes may stand out above the rest.

Metformin used alone is still the best for lowering blood sugar and preventing complications of type 2 diabetes in people who are overweight or obese, according to a new review.

Researchers analyzed 29 major trials of metformin (brand name Glucophage).

"Our review of the literature suggests that metformin is a good first-line therapy for overweight or obese people with type 2 diabetes," researcher Antonio Saenz, MD, concludes.

Best for Weight Loss

There are now more than a dozen blood sugar-lowering or insulin-sensitizing medications approved for the treatment of type 2 diabetes. Metformin won FDA approval as a medication to treat type 2 diabetes in the mid-1990s, but it has been widely used in Europe for decades.

The newly published analysis did not compare metformin head-to-head with many of the newer drugs. But it is widely recognized to have weight loss benefits for overweight people with diabetes that the newer drugs may not have.

Though many of the newer drugs may promote weight gain, metformin has been associated with modest weight losses in people with type 2 diabetes.

"Metformin is generally considered to be the first-line treatment for overweight diabetics, but the main message is that these people should do whatever it takes to get keep their blood sugar under control," American Diabetes Association (ADA) president Robert Rizza, MD, tells WebMD.

Some patients respond well to one medication alone such as metformin, while others do better on a combination of medications used to treat diabetes, he says. And some patients do not tolerate metformin because of side effects, which can include severe stomach cramps, nausea, and diarrhea.

"All things being equal, [metformin] is probably the drug that most people should start with, but if they can't take it there is something else out there," Rizza says. "The vast majority of people can normalize or nearly normalize their blood sugar with the medications we have today."

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Independent Review

The new analysis was published under the auspices of the Cochrane Collaboration, an international, nonprofit research group that reviews health care interventions. The results were published in the July 20 issue of the Cochrane Database of Systematic Reviews.

The 29 studies compared intensive blood-sugar control using metformin with other interventions including diet, placebo, and several other types of medications for diabetes, including insulin.

Researchers reported that obese patients who took metformin alone tended to achieve significant benefit in blood-sugar control, weight loss, cholesterol, and blood pressure.

A greater benefit was seen in obese patients taking metformin for any diabetes-related outcomes -- such as diabetes-related death, all causes of death, and heart attacks -- compared to overweight patients given other therapies.

When metformin was compared to diet and placebo a strong benefit was seen in overall glucose control based on a three-month measure known as a HbA1c.

A moderate benefit was seen when compared to other older diabetes drugs that increase the production of insulin, known as sulfonylureas. These benefits included better blood-sugar control, lowering LDL "bad" cholesterol, and a reduction in body mass index (BMI) or weight loss.

Saenz and colleagues concluded that well-designed studies are needed comparing metformin with the newer diabetes drugs in specific subgroups of people with type 2 diabetes. Among the biggest unanswered questions: Is the older drug really better for preventing heart attacks and strokes in patients who are overweight, elderly, or have other heart disease risk factors?

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By Salynn Boyles, reviewed by Brunilda Nazario, MD

SOURCES: Saenz, A. Cochrane Database of Systematic Reviews, July 20, 2005; online edition. Antonio Saenz, MD, internist, family physician, Madrid, Spain. Robert Rizza, MD, president, American Diabetes Association; director for research, Mayo Clinic, Rochester, Minn.