RESUMEN
BACKGROUND: This study investigated the safety and efficacy of metformin up-titration in Japanese patients with type 2 diabetes mellitus treated with vildagliptin (100 mg/day) and low-dose metformin (500 or 750 mg/day). RESEARCH DESIGN AND METHODS: Fifty patients were randomly allocated to the control group (maintaining the initial low-dose of metformin) and the dose increase group (up-titrating of metformin to 1,500-2,250 mg/day) for 24 weeks. The primary outcome was change in HbA1c from baseline to 24 weeks. RESULTS: Among the 25 patients allocated to the dose increase group, four patients were not able to complete the study protocol because of gastrointestinal symptoms. HbA1c in the dose increase group was significantly but modestly lower than in the control group (change in HbA1c: 0.22 ± 0.57 vs. -0.15 ± 0.58%, group comparison, P < 0.05). The dose increase group did not gain weight during the study period, and no hypoglycemic events were reported in both groups. The rate of gastrointestinal symptoms in the dose increase group was profoundly higher than in the control group (32 vs. 0%, P < 0.01). CONCLUSIONS: In Japanese patients with type 2 diabetes treated with vildagliptin and low-dose metformin, metformin up-titration significantly but modestly improved glycemic control without hypoglycemia and weight gain.