Diabetes Drug Safer for More Patients

Metformin for type 2 diabetes lowers risks in patients with mild to moderate kidney impairment

/ Author:  / Reviewed by: Robert Carlson, M.D

(RxWiki News) Metformin (often the first drug of choice for treating type 2 diabetes) is not prescribed to patients with kidney problems for fear of serious risks. New research suggests these risks might be overrated.

In a recent study on patients with type 2 diabetes, metformin worked better than other diabetes drugs at lowering the risk of heart disease, serious infection and death in patients with normal kidney function and patients with mild kidney problems.

"Seek treatment if you have diabetes."

Metformin was the first drug created to treat diabetes. Today, it remains one of the most commonly prescribed diabetes drugs. However, the risk of a rare but life-threatening condition - called lactic acidosis - keeps doctors from prescribing metformin to patients with lower kidney function.

With this possible risk in mind, Nils Ekström, MD, of the University of Gothenburg in Sweden, and colleagues set out to test the effectiveness and safety of metformin in type 2 diabetes patients with different levels of kidney patients.

They found that type 2 diabetes patients taking metformin had a lower risk of heart disease and death compared to patients taking insulin.

Patients taking metformin also had a lower risk of death compared to those taking other oral diabetes drugs.

Previously, metformin was thought to increase the risk of acidosis in people with kidney problems. But Dr. Ekström and colleagues found this may not be the case.

Acidosis is a condition in which too much acid builds up in the body's fluids. If a person's kidneys are not working properly, they cannot filter out these acids.

In this study, patients with mild to moderate kidney function problems did not have an increased risk of acidosis.

In addition, the researchers found that patients with reduced kidney function taking metformin did not have an increased risk of heart disease or death.

Because metformin did not seem to raise the risk of serious side effects in patients with kidney impairment, the drug may be prescribed to many more diabetes patients than is the case now, said Dr. Ekström.

Still, he cautioned not to take the study's findings too far.

"It is important to keep in mind that the results are for patients with mild to moderate kidney impairment. Metformin still cannot be recommended for patients with severe kidney impairment and should be prescribed with great caution for those patients," he said.

The study included 51,675 men and women with type 2 diabetes. The researchers compared the risks associated with taking metformin alone, other oral diabetes drugs and insulin.

Compared to patients taking metformin, those taking other oral diabetes drugs had a higher risk of death from all causes, with a hazard ratio of 1.13.

A hazard ratio explains how often an event happens in one group versus another. A hazard ratio of more than 1.0 means the event happens more in one group than the other. In this case, the hazard ratio of 1.13 means that death is more likely in patients taking other oral diabetes drugs than in those taking metformin.

Results also showed that a slightly increased risk of heart disease in patients taking other oral diabetes drugs compared to patients taking metformin, with a hazard ratio of 1.02. However, this hazard ratio does not show a significant difference in risk.

Compared to metformin patients, insulin patients had an increased risk of heart disease, with a hazard ratio of 1.18. Insulin patients also had an increased risk of death from all causes, with a hazard ratio of 1.34.

In people with mild kidney impairment, metformin use was associated with a lower risk of acidosis or serious infection, with a hazard ratio of 0.85. Metformin was also linked to a lower risk of death from all causes in patients with mild kidney impairment, with a hazard ratio of 0.87.

These findings suggest that metformin may be safer than previously thought.

"In clinical practice, the benefits of metformin use clearly outbalance the risk of severe side effects," the authors concluded.

The study was funded by the Region Västra Götaland and the Swedish Association of Local Authorities and Regions fund and the National Diabetes Register (NDR). The NDR is supported by the Swedish Society for Diabetology and the Swedish Diabetes Association.

Co-author Björn Zethelius is employed by the Medical Products Agency (MPA) in Sweden. Co-author Björn Eliasson has served as a lecturer for all pharmacological companies manufacturing glucose-lowering drugs and participated in advisory boards for Eli Lilly, Sanofi and Boeringer Ingelheim among others.

The study was published July 13 in BMJ Open.

Reviewed by: 
Review Date: 
September 16, 2012
Last Updated:
September 19, 2012