Addition of Metformin to Liraglutide, A GLP-1 Receptor Agonist, Improves Glycemic Control in Patients with Type 2 Diabetes Mellitus

Background: The maximum permissible dose of liraglutide, a GLP-1 receptor agonist, under the Japanese Heath Insurance system is 0.9 mg/day. We determined the effects of adding metformin to liraglutide therapy in Japanese patients with type 2 diabetes. Material and Methods: This observational retrospective study included 47 patients with type 2 diabetes who were treated with liraglutide alone or in combination with sulfonylureas. Metformin was added at a dose ranging from 250 to 500 mg/day based on inadequate glycemic control. Liraglutide and metformin doses were converted from mg/day to mg/kg body weight/day before analysis of the correlation between the dose and changes in glycated hemoglobin (HbA1c) and body mass index (BMI). Results: Both HbA1c and BMI decreased significantly after 24 weeks of the combination treatment. Mild gastrointestinal adverse events were reported by 21% of the patients. Only the dose of metformin, but not that of liraglutide, expressed in mg/kg body weight was correlated significantly with decrease in HbA1c and BMI. Conclusions: The addition of metformin to the maximum permissible dose of liraglutide helps secure glycemic control and reduce BMI in Japanese patients with type 2 diabetes who exhibit inadequate response to liraglutide.