Long-term therapy with addition of pioglitazone to metformin compared with the addition of gliclazide to metformin in patients with type 2 diabetes: a randomized, comparative study

Background: This 52-week, randomized, double-blind study compared the efficacy and safety of metformin plus pioglitazone with the established combination of metformin plus gliclazide in type 2 diabetes mellitus.

Methods: Patients with poorly controlled type 2 diabetes (HbA1c > or = 7.5% to < or =11.0%) received either pioglitazone 15 mg o.d. (titrated up to 45 mg; n = 317) or gliclazide 80 mg o.d. (titrated up to 320 mg; n = 313) and metformin at the pre-study dose. HbA1c, fasting plasma glucose (FPG), insulin, lipids and the urinary albumin/creatinine ratio were measured.

Results: There were no significant differences in HbA1c (1% decrease in both groups) and FPG between groups. There was a decrease in fasting insulin in the pioglitazone group compared to an increase in the gliclazide group (p < 0.001). There were significantly greater improvements in triglycerides and HDL-cholesterol in the metformin plus pioglitazone group compared to the metformin plus gliclazide group (p < 0.001). Mean LDL-cholesterol decreased with metformin plus gliclazide and increased with metformin plus pioglitazone (p < 0.001); however, this increase was considerably less marked than that in HDL-cholesterol. The mean urinary albumin/creatinine ratio was reduced by 10% in the metformin plus pioglitazone group compared to an increase of 6% in the metformin plus gliclazide group (p = 0.027). The incidence of adverse events was comparable between groups and both combinations were well tolerated.

Conclusions: Compared to the established combination of metformin plus gliclazide, this study indicates potential benefits of addition of pioglitazone to metformin in terms of improvements in microalbuminuria and specific abnormalities associated with diabetic dyslipidemia.