A new review of studies confirms that the drug metformin should be in the first line of defense against type 2 diabetes.

Using metformin alone can improve control of blood glucose, while also reducing risk factors for heart disease such as excess body weight, cholesterol levels and hypertension, the review found.

The systematic evidence review included 29 trials comparing the benefits of metformin to placebo, dietary changes, other oral medications and insulin therapy. The studies comprised a total of 5,259 participants and had a minimum follow-up period of three months.

"This systematic review suggests the utility of metformin monotherapy as first-line therapy in the management of type 2 diabetes and … the prevention of its vascular complications," say the authors, led by Dr. Antonio Saenz, an internist in Madrid. In type 2 diabetes, insulin produced by the pancreas is not able to get sugar from the blood into the body's energy-hungry cells.

Metformin normalizes blood sugar by increasing uptake in the liver, muscle, fat, and other tissues. Systematic reviews draw evidence-based conclusions about medical practice after considering both the content and quality of existing medical trials on a topic. The review added more recent trials of metformin since completion of the landmark 1998 United Kingdom Prospective Diabetes Study (UKPDS), the largest and longest diabetes study undertaken to date. It focused on the same health outcomes as the earlier study: diabetes-related problems such as heart attack, stroke, kidney failure, nerve damage, amputation, blindness and death.

"The eight additional trials reporting primary outcomes do not change any of the conclusions of the UKPDS," conclude the review authors. "In overweight type 2 diabetics, intensive metformin shows more benefit than [other drugs] or insulin therapy, for reducing the risk for any clinical end point related to type 2 diabetes, all-cause mortality and stroke."

"Our review confirms that tight glycemic control with metformin monotherapy is one of the main therapeutic options in the type 2 diabetes mellitus in patients with overweight or obesity," they say. In addition, they confirm that the adverse effects of metformin, mainly on the digestive tract, are not life-threatening. Metformin first became available in Europe in 1979, but was not cleared for use in the United States until 1994 due to concerns about a potentially fatal complication called lactic acidosis. Diabetes takes a severe toll on blood vessels throughout the body, especially when combined with other cardiovascular risk factors. Two out of three people with diabetes die from heart disease and stroke, according to the American Diabetes Association.

Source: Diabetes In Control.com: Saenz A et al. Metformin Monotherapy for Type 2 Diabetes Mellitus. The Cochrane Database of Systematic Reviews 2005, Issue 3.