Metformin remains the medication of first choice in treating type 2 diabetes

Research Activities, July 2011, No. 371

The U.S. Food and Drug Administration has approved 11 unique classes of drugs to treat hyperglycemia (high blood-sugar levels) in patients with type 2 (adult-onset) diabetes. However, compared with other oral diabetes medications, metformin by itself or in a two-drug combination continues to have high benefits, according to an updated review of studies. The researchers note that this is consistent with the findings of a 2007 review that included fewer medications and comparisons. Even after including newer studies, the evidence for long-term clinical outcomes such as all-cause mortality, cardiovascular disease, or neuropathy, was limited, the researchers report.

Most medications reduced the level of glycosylated hemoglobin (hemoglobin A1C, an indicator of average blood-sugar level over a period of months) equally by 1 percent; and most two-drug combinations produced similar reductions. Metformin caused less weight gain compared with either the thiazolidinediones or sulfonylureas. Metformin decreased low-density lipoprotein levels compared with pioglitazone, sulfonylureas, and DPP-4 inhibitors.

With regard to medication risks, patients taking sulfonylureas had a fourfold higher risk of mild or moderate hypoglycemia (low blood sugar) compared with metformin alone, and patients taking metformin plus sulfonylureas had more than a fivefold higher risk of this adverse effect than did those taking metformin plus thiazolidinediones. However, thiazolidinediones increased the risk of congestive heart failure compared with sulfonylureas, and increased risk of bone fractures compared with metformin. Patients taking metformin were more likely to develop diarrhea than those taking thiazolidinediones or sulfonylureas.

Using search criteria similar to those for the 2007 review, the researchers found 166 studies for inclusion, which included 71 studies from the earlier review. The study was funded by the Agency for Healthcare Research and Quality (Contract No. 290-02-0018) to the Johns Hopkins University Evidence-based Practice Center.

More details are in "Comparative effectiveness and safety of medications for type 2 diabetes: An update including new drugs and combinations," by Wendy L. Bennett, M.D., M.P.H., Nisa M. Maruthur, M.D., M.H.S., Sonal Singh, M.D., M.P.H., and others in the May 3, 2011 Annals of Internal Medicine 354(9).

Current as of July 2011
Internet Citation: Metformin remains the medication of first choice in treating type 2 diabetes: Research Activities, July 2011, No. 371. July 2011. Agency for Healthcare Research and Quality, Rockville, MD.