Adherence to a Fixed-Dose Combination of Rosiglitazone/Glimepiride in Subjects Switching from Monotherapy or Dual Therapy with a Thiazolidinedione and/or a Sulfonylurea

Abstract

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 A1c (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.