Disparities in the Efficacy of Metformin in Combination with Dipeptidyl Peptidase-4 Inhibitor as Initial Treatment Stratified by Dosage and Ethnicity: A Meta-Analysis

As initial combination therapy of metformin and dipeptidyl peptidase-4 (DPP-4) inhibitor, the efficacy and safety for the use of high dose of metformin or low dose of metformin and the efficacy and safety for the combination use for Asian and Caucasian patients were not clear.Double-blind randomized controlled trials comparing the efficacy of initial combination therapy of metformin and DPP-4 inhibitors with metformin monotherapy were included. The primary outcome was a result of comparisons between high-dose combination therapy and low-dose combination therapy in terms of efficacy and safety.A total of 11 studies were included. The results indicated that the high-dose combination therapy showed significant decreases in hemoglobin A1c (HbA1c) (-0.32%, P < 0.05), fasting plasma glucose (FPG) (-0.63 mmol/L, P < 0.05), and postprandial glucose (PPG) (-0.99 mmol/L, P < 0.05), but less increase in body weight (-0.54 kg, P < 0.05) when compared with low-dose combination therapy, corrected by metformin monotherapy. Moreover, the high-dose combination therapy exhibited significant decreases in HbA1c (-0.24%, P < 0.05), FPG (-0.54 mmol/L, P < 0.05), and PPG (-0.94 mmol/L, P < 0.05) in the Caucasian population than in the Asian population, corrected by metformin monotherapy.As an initial treatment, the high dose of metformin in combination with DPP-4 inhibitors not only provided better glycemic control but also had less effect on weight gain compared with the low-dose combination therapy through the correction of metformin monotherapy. Moreover, initial combination therapy in the Caucasian population showed better glycemic control and less increase in body weight compared with the Asian population.