AHRQ's comparative effectiveness research on oral medications for type 2 diabetes: a summary of the key findings.

BACKGROUND: In 2007, the Agency for Healthcare Research and Quality(AHRQ) published a systematic review on the comparative effectiveness of oral medications for type 2 diabetes. The review included studies on the benefits and risks of oral medications used for achieving glycemic control in patients with type 2 diabetes. AHRQ published an updated review in March 2011 that summarized the benefits and harms of medications (metformin,second-generation sulfonylureas, thiazolidinediones, meglitinides,dipeptidyl peptidase-4 (DPP-4) inhibitors and glucagon-like peptide-1 (GLP-1) receptor agonists), as monotherapy and in combination, for the treatment of adults with type 2 diabetes.
OBJECTIVES: To (a) familiarize health care professionals with the methods and findings from AHRQ's 2011 comparative effectiveness review on medications for adults with type 2 diabetes, (b) encourage consideration of the clinical and managed care applications of the review findings, and(c) identify limitations and gaps in the existing research with respect to the benefits and risks of oral diabetes medications.
SUMMARY: Type 2 diabetes mellitus is a major public health burden. Since the 2007 AHRQ systematic review of oral medications for type 2 diabetes, the FDA has approved several new drug classes. Therefore, in 2011, the original systematic review was updated with comparisons including the newer oral diabetes medications. The updated report expands beyond the scope of the original 2007 review by including comparisons of 2-drug combinations and the addition of more head-to-head comparisons, as well as additional adverse outcomes. A high strength of evidence showed that most medications were similarly efficacious at lowering hemoglobin A1c by about 1 absolute percentage point compared with baseline values. The addition of most oral medications to initial monotherapy further improved glycemiccontrol by lowering A1c by another 1 percentage point. The only exception was the DPP-4 inhibitor class, which did not lower A1c to the same extent as metformin when used as monotherapy. Overall, metformin was found to have a more favorable effect on body weight when compared with other medications. Two-drug combinations compared with each other demonstrated similar reductions in A1c levels. Metformin decreased low-density lipoprotein cholesterol (LDL-C) relative to pioglitazone, sulfonylureas,and DPP-4 inhibitors. Sulfonylureas had a 4-fold higher risk of mild-to-moderate hypoglycemia compared with metformin alone, and, in combination with metformin, had more than a 5-fold increased risk compared with metformin plus a thiazolidinedione. Thiazolidinediones had an increased risk of congestive heart failure relative to sulfonylureas, and an increased risk for bone fractures relative to metformin. Diarrhea occurred more often for metformin users compared with thiazolidinedione users. Although the long-term risks and benefits of diabetes medications remain unclear, the evidence supports the use of metformin as a first-line agent.