Combination therapy with pioglitazone plus metformin or sulfonylurea in patients with Type 2 diabetes: Influence of prior antidiabetic drug regimen

Purpose: To evaluate two trials of combination therapy, pioglitazone together with metformin or sulfonylurea, for Type 2 diabetes mellitus and to examine how pretrial antidiabetic therapies may have influenced the results. Subjects and Methods: The results of two published trials that examine combination therapy, pioglitazone plus metformin or pioglitazone plus sulfonylurea were analyzed. A post hoc analysis was performed in which patients from both of these trials were subdivided on the basis of their oral antidiabetic therapy before enrollment into the trials. Those subsets receiving pretrial therapy with a sulfonylurea plus metformin - and discontinuing one of the agents before randomization - were compared to those receiving only one of the agents before enrollment. Results: Patients in the combination pioglitazone (30 mg/day) plus metformin therapy arm of one trial, who entered with stable metformin monotherapy, experienced a significant decrease in glycosylated hemoglobin (HbA_1C) levels during the 16-week course of the trial (-1.0±0.1 [mean±S.E.] percentage points; P1C levels (0.2±0.2 percentage points; P>.05). The difference between groups was significant (P1C levels (-1.0±0.1 and -1.4±0.1 percentage points, respectively, for the 15- and 30-mg pioglitazone arms; P1C levels. Differences between the groups separated on the basis of pretrial antidiabetic regimen were significant (P