Triple Combination Therapy Using Metformin, Thiazolidinedione, and a GLP-1 Analog or DPP-IV Inhibitor in Patients with Type 2 Diabetes Mellitus

Although there is no HbA1c threshold for cardiovascular risk, the American Diabetic Association-recommended goal of HbA1c < 7.0% appears to be unacceptably high. To achieve an optimal HbA1c level goal of 6.0% or less, a high dosage of sulfonylureas and insulin would be required; the trade-off would be the common adverse effects of hypoglycemia and weight gain. In contrast, hypoglycemia is uncommon with insulin sensitizers and GLP-1 analogs, allowing the physician to titrate these drugs to maximum dosage to reduce HbA1c levels below 6.0% and they have been shown to preserve β-cell function. Lastly, weight gain is common with sulfonylurea and insulin therapy, whereas GLP-1 analogs induce weight loss and offset the weight gain associated with TZDs. A treatment paradigm shift is recommended in which combination therapy is initiated with diet/exercise, metformin (which has antiatherogenic effects and improves hepatic insulin sensitivity), a TZD (which improves insulin sensitivity and preserves β-cell function with proven durability), and a GLP-1 analog (which improves β, α-cell function and promotes weight loss) or a dipeptidyl peptidase IV inhibitor in patients with type 2 diabetes mellitus.