Background: Little is known about the potential for improved adherence with and cost savings of fixed-dose combination therapy (FDCT) products compared with analogous dual therapy for type 2 diabetes mellitus.
Objectives: The objectives of this study were as follows: (1) to describe patient adherence to various oral antidiabetic regimens (ie, dual therapy and FDCT); (2) to determine whether there is a difference in medication adherence between FDCT users and analogous dual-therapy users; and (3) to assess whether there is a difference in reimbursement amounts between an FDCT product and its individual components.
Methods: This study was a retrospective cohort analysis using the Texas Medicaid prescription claims database. The study subjects included those who used antidiabetic FDCT or dual therapy from August 1, 2000, to July 31, 2004. The identification period of study subjects was between August 1, 2000, and July 31, 2004, including 12 months before and after the index date, so that the overall time frame was from August 1, 1999, through July 31, 2005. Prescription claims were analyzed over a 12-month preindex and 12-month postindex period. Adherence was measured using medication possession ratio (MPR), and regimen costs per tablet were assessed utilizing the index prescription.
Results: Overall, 7570 FDCT users and 14,762 dual-therapy users were identified. Regarding the postindex period, FDCT users had 1.8% higher MPR compared with dual-therapy users (78.6% vs 77.2%). Patients who switched from monotherapy to FDCT had a 1.5% decrease in adherence (from 79.7% to 78.5%), whereas those who switched from monotherapy to dual therapy had a 10.0% decrease in adherence (from 83.0% to 74.7%). Those who switched from dual therapy to FDCT had a 12.4% increase in adherence (from 72.7% to 81.7%). Multivariate logistic regression analyses revealed that among preindex monotherapy users, FDCT users were significantly more likely to have higher adherence than dual-therapy users (odds ratio [OR] = 1.867; 95% CI, 1.716-2.032) after controlling for covariates, and the results were similar among preindex dual-therapy users (OR = 1.551; 95% CI, 1.204-1.999). From the perspective of the third-party payer, all FDCT products were significantly less expensive than their equivalent individual components (P < 0.001).
Conclusions: Among these Texas Medicaid beneficiaries, antidiabetic FDCT users were more adherent to their regimen than dual-therapy users, and FDCT was less expensive than the analogous dual therapy. Because multiple agents are often required to achieve adequate glycemic control, it may be clinically and economically beneficial to treat eligible patients with FDCT products.