Background: In 2005, a fixed-dose combination therapy (FDCT) of rosiglitazone maleate and glimepiride became available for treatment of type 2 diabetes mellitus. It is hypothesized that FDCTs increase adherence by decreasing the number of required tablets.
Objective: To assess changes in medication adherence and hemoglobin A(1c) (A1C) values in subjects switching from monotherapy with either a sulfonylurea or rosiglitazone or dual therapy with both to rosiglitazone/glimepiride FDCT.
Methods: This retrospective database analysis included subjects with 1 or more prescription fills for rosiglitazone, a sulfonylurea, or rosiglitazone/glimepiride FDCT during the identification period of January 1, 2006, to September 30, 2006. Subjects were grouped according to baseline and follow-up period treatment regimens: sulfonylurea or rosiglitazone monotherapy switched to sulfonylurea and rosiglitazone dual therapy (Mono/Dual), monotherapy to rosiglitazone/glimepiride FDCT (Mono/FDCT), sulfonylurea and rosiglitazone dual therapy in both periods (Dual/Dual), and dual therapy to rosiglitazone/glimepiride FDCT (Dual/FDCT). The medication possession ratio (MPR) was calculated as a measure of adherence. The change in A1C from the baseline period to the follow-up period was assessed for each cohort.
Results: The study included 16,490 subjects. From baseline to follow-up, MPR decreased for both the Mono/FDCT cohort and the Mono/Dual cohort, but the magnitude of this decrease was less for the Mono/FDCT cohort (-0.02 vs -0.10; p < 0.001). Mean MPR significantly improved for the Dual/FDCT cohort compared with the Dual/Dual cohort (+0.10 vs +0.05; p < 0.001). The mean absolute A1C reduction did not differ significantly between the Mono/FDCT cohort (-1.08%) and the Mono/Dual cohort (-0.77%). Compared with the Dual/Dual cohort, the Dual/FDCT cohort experienced a greater absolute reduction in A1C (-0.06% vs -0.51%; p = 0.004). The results remained statistically significant in the multivariate model.
Conclusions: Switching to rosiglitazone/glimepiride FDCT, in comparison with switching to dual therapy, was associated with improvements in medication adherence and glycemic control.