Adherence to a fixed-dose combination of rosiglitazone maleate/metformin hydrochloride in subjects with type 2 diabetes mellitus: a retrospective database analysis.

BACKGROUND

In 2002, fixed-dose combination therapy (FDCT) with rosiglitazone maleate plus metformin hydrochloride became available for the treatment of type 2 diabetes mellitus (DM-2) in subjects whose disease was uncontrolled on monotherapy with metformin or a thiazolidinedione. FDCT allows a reduced pill burden and a less complex medication regimen.

OBJECTIVE

The objective of this study was to assess changes in medication adherence rates associated with oral hypoglycemic agents in subjects switching from either monotherapy or dual therapy with metformin and/or rosiglitazone to rosiglitazone-metformin FDCT.

METHODS

In this retrospective database analysis, data were obtained from the pharmacy claims database of a large health benefits company. Prescription claims for subjects aged > or =18 years with DM-2 whose disease was uncontrolled on monotherapy with metformin or a thiazolidinedione were analyzed over a 12-month study period (a 6-month preindex period and a 6-month postindex period). Some subjects were receiving monotherapy with either metformin or rosiglitazone during the preindex period and remained on monotherapy throughout the postindex period (Mono/Mono cohort), switched to dual therapy with both agents (Mono/Dual cohort), or switched to FDCT (Mono/FDCT cohort). Some subjects were receiving dual therapy with metformin and rosiglitazone during the preindex period and remained on dual therapy throughout the postindex period (Dual/Dual cohort) or switched to FDCT (Dual/FDCT cohort). A medication possession ratio (MPR)-a proxy measurement of medication adherence-was calculated for each subject for each period. Changes in medication adherence were compared using a general linear model.

RESULTS

Overall, data from the records of 16,928 subjects (8499 men, 8429 women; mean [SD] age, 58.12 [11.97] years) were included in this study. There was significantly less reduction in the MPR change for the Mono/FDCT cohort compared with the Mono/Dual cohort (-4.6% vs -12.4%; P < 0.001). There was significant improvement in the mean MPR change for the Dual/FDCT cohort compared with the Dual/Dual cohort (3.5% vs -1.3%; P < 0.005).

CONCLUSIONS

The results of this retrospective database analysis suggest that rosiglitazone-metformin FDCT yielded significant improvements in medication adherence rates compared with dual therapy regimens.