Comparison of extended-release metformin in combination with a sulfonylurea (glyburide) to sulfonylurea monotherapy in adult patients with type 2 diabetes: a multicenter, double-blind, randomized, controlled, phase III study.

BACKGROUND: Metformin is widely used in the management of type 2 diabetes, either as monotherapy or in combination with other oral antihyperglycemic agents such as sulfonylureas and thiazolidinediones. Combination treatment with metformin and sulfonylurea in patients who failed monotherapy has been reported to be effective in maintaining glycemic control.

OBJECTIVE: The purpose for this study was to compare the efficacy and tolerability of extended-release metformin (MER) administered with a sulfonylurea (glyburide) to sulfonylurea monotherapy in patients with type 2 diabetes.

METHODS: This multicenter, double-blind, randomized, controlled study enrolled adult patients with type 2 diabetes who were either drug naive or previously treated with oral diabetic medications and who had not achieved glycemic control. Patients were stabilized on sulfonylurea (10 mg/d for 2 weeks, then 15 mg/d for 4 weeks) then randomly assigned at base line to receive MER (1500 mg QD, 1000 mg BID, or 2000 mg QD) plus sulfonylurea (MER+S) or sulfonylurea monotherapy for 24 weeks. Patients were evaluated every 1 to 2 weeks during sulfonylurea stabilization and initial metformin treatment, and then every 4 weeks until study end. The primary efficacy end point was glycemic control as determined by changes in glycosylated hemoglobin (HbA(1c)) from baseline to study end between those receiving combination MER+S treatment and those receiving sulfonylurea monotherapy. Adverse events (AEs) were recorded throughout the study by direct questioning, self-reporting by patients, and from the results of physical examinations and clinical laboratory tests.

RESULTS: A total of 741 patients were enrolled. Of these, 134 patients were stabilization failures, 607 patients were randomized, 575 patients received treatment and were included in the intent-to-treat population, and 417 patients completed the study per protocol. There were no significant differences between treatment groups for any demographic or baseline characteristics (all patients: mean [SD] age, 53.0 [10.6] years; male sex, 54.6% [314/575]; race, white, 58.8% [338/575], Hispanic, 28.5% [164/575]; mean [SD] weight, 97.0 [22.2] kg; obese [body mass index > or =30 kg/m(2)], 69.4% [399/575] ). There were significant decreases from baseline in mean fasting plasma glucose (FPG) levels by the end of week 1 and in mean HbA(1c) levels by week 8 in each MER+S group (both, P < 0.001). The mean (95% CI) changes from baseline to study end in the combined MER+S groups (HbA(1c), -0.74% [-0.85% to -0.64%]; FPG, -12.9 [-17.1 to -8.7] mg/dL) were significantly different from the sulfonylurea monotherapy group (HbA(1c), 0.08% [-0.08% to 0.25%]; FPG, 15.5 [8.2 to 22.8] mg/dL; P < 0.001). Among patients treated with MER+S, the mean (SEM) change in HbA(1c) was -1.26% (-1.44% to -1.07%) for drugnaive patients and -0.59% (-0.46% to 0.71%) for patients previously treated with metformin. There was a significant difference between treatment groups with regard to the prevalence of hypoglycemia (MER+S groups, 11.6% vs sulfonylurea monotherapy group, 4.2%; P = 0.007), but no significant difference was observed for gastrointestinal events. The most common gastrointestinal AEs were diarrhea and nausea (8.6% and 3.9%, respectively, in the combined MER+S groups; 2.8% and 1.4%, respectively, in the sulfonylurea monotherapy group).

CONCLUSIONS: The combination of QD or BID treatment with MER+S was significantly more effective in lowering HbA(1c) and glucose levels than sulfonylurea monotherapy in these adult patients with type 2 diabetes. However, a significant increase in the prevalence of hypoglycemia was observed in the MER+S treatment groups compared with the sulfonylurea monotherapy group.