Efficacy and safety of therapy with metformin plus pioglitazone in the treatment of patients with type 2 diabetes: a double-blind,placebo-controlled,clinical trial

ABSTRACT

Objective: To assess the efficacy and safety of combination therapy with pioglitazone and metformin in Japanese patients with type 2 diabetes.

Research design and methods: During a 12-week observation period 236 patients were treated with metformin 500 or 750?mg/day. 169 patients with a confirmed HbA_1c level ≥ 6.5% were randomized (stratified according to metformin dosage) to receive pioglitazone 15?mg/day for 12 weeks then increased to 30?mg/day for a further 16 weeks (n?=?83), or placebo (n?=?86). Outcome measures included HbA_1c, fasting blood glucose (FBG), percentage of patients achieving HbA_1c?<?6.5%, lipid profile, and other metabolic parameters.

Results: Mean HbA_1c was reduced by 0.67% in patients receiving pioglitazone plus metformin versus an increase of 0.25% in those receiving metformin alone (p?<?0.0001). After 8 weeks’ treatment and until the end of the study, HbA_1c was significantly lower with pioglitazone plus metformin and more patients in this group achieved an HbA_1c?<?6.5% (38.6% vs. 8.1%; p?<?0.0001). FBG was also reduced by a significantly greater amount in patients receiving pioglitazone plus metformin compared with metformin monotherapy (?20.5 vs. 1.9?mg/dl; p?<?0.0001). Combination therapy was associated with significantly increased HDL-cholesterol, total cholesterol, and adiponectin, and significantly decreased levels of fasting insulin, free fatty acids, and homeostasis model assessment insulin resistance (HOMA-R) compared with metformin monotherapy. Overall, combination therapy and monotherapy were equally well tolerated and the incidence of adverse effects ‘possibly’ related to therapy was 15.7% and 11.6% (p?=?0.505), respectively. Edema occurred slightly more often in the combination group (6.0 vs. 1.2%).

Conclusion: Pioglitazone plus metformin significantly improved glycemic control (HbA_1c and FBG), and markers associated with increased insulin resistance and cardiovascular risk compared with metformin monotherapy.

Clinical trial registration number: UMIN 000001110.