Comparative effects of vildagliptin and sitagliptin determined by continuous glucose monitoring in patients with type 2 diabetes mellitus

The dipeptidyl peptidase-4 inhibitors vildagliptin and sitagliptin are effective in treating patients with type 2 diabetes mellitus. Patients receiving standard doses of sitagliptin plus insulin may require increased doses of sitagliptin or switching to vildagliptin to improve blood glucose control. This study compared the effects of increasing sitagliptin and switching to vildagliptin in type 2 diabetes patients receiving standard doses of sitagliptin plus insulin. This prospective, randomized, parallel-group comparison trial enrolled 33 type 2 diabetes patients receiving 50 mg sitagliptin once daily plus insulin. Seventeen patients were randomized to 50 mg vildagliptin twice daily, and 16 to 100 mg sitagliptin once daily, and evaluated by continuous glucose monitoring at baseline and after 8 weeks. The primary end-point was the change in mean amplitude of glycemic excursions (MAGE). MAGE decreased from baseline in both the vildagliptin (-13.4 ± 35.7 mg/dL) and sitagliptin (-8.4 ± 24.3 mg/dL) groups, but neither within- nor between-group changes were statistically significant. Similarly, the areas under the curve for blood glucose levels ≥180 mg/dL and <70 mg/dL tended to improve in both groups, but these differences were not statistically significant. In contrast, HbA1c was significantly reduced only in the vildagliptin group, from 7.1 ± 0.6% at baseline to 6.8 ± 0.6% at 8 weeks (p=0.006). Increasing sitagliptin dose and switching to vildagliptin had limited effects in improving MAGE in type 2 diabetic patients treated with standard doses of sitagliptin.