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Abstract
Objective:
To evaluate the impact of angiotensin receptor blocker (ARBs)/dihydropyridine calcium channel blockers (CCBs) single-pill combination (SPC) on adherence to antihypertensive treatment in comparison to free combination of ARBs and CCBs.
Research design and methods:
A retrospective data analysis was performed using pharmacy claims data from a national pharmacy benefit management company. The study included patients who were newly initiated on ARB/CCB treatment between 01/01/2007 and 08/31/2008, aged ≥18 years, and continuously enrolled in the same health plan for 12 months prior to and 13 months after starting ARB/CCB treatment. Outcome variables were persistence, defined as time to discontinuation of therapy, and adherence, defined as proportion of days covered (PDC) ≥ 0.80. Propensity score weighting was used to balance the characteristics of the two groups.
Results:
The final sample contained 2312 patients in the free-combination group and 2213 patients in the SPC group. Patients in the SPC group and the free-combination group were different in age, gender, type of insurance, history of antihypertensive therapy and co-morbidities. These differences were largely normalized after propensity score adjustment. Multivariate logistic model regression showed that patients in the SPC group had a 90% greater odds of being adherent to index therapy compared to patients in the free-combination group (odds ratio [OR] 1.90, 95% confidence interval [CI] 1.75–2.08, p < 0.001). A Cox proportional hazards model showed that patients in the SPC group were less likely to discontinue ARB/CCB SPC therapy compared to patients in the free-combination group (hazard ratio [HR] 0.66, 95% CI 0.63–0.70, p < 0.001). In both models, higher copayment (copayment $50 and above) was associated with worse persistence and adherence in comparison to patients who had a lower copayment ($0-$5): HR = 1.23, p < 0.001 and OR = 0.67, p < 0.001.
Conclusion:
Patients using SPC ARB/CCB therapy were more likely to be persistent and adherent to treatment compared to patients taking free-combination therapy.
Transparency
Declaration of funding
Funding for this research was provided by Novartis Pharmaceuticals Corporation.
Declaration of financial/other relationship
F.Z. and B.V. have disclosed that they are employees of MedImpact Healthcare Systems, Inc, which received payments from Novartis for the research and for the development of the manuscript. L.A., A.R. and F.F.T have disclosed that they are employees of Novartis Pharmaceuticals Corporation.
Acknowledgments
The first draft of this manuscript was developed by F.Z. All authors provided comments for scientific interpretation and approved the final draft for submission. The authors are grateful for the programming support provided by Sara Yuewen Gao of MedImpact.
Part of the findings in this paper were presented at the American Heart Association Quality of Care and Outcomes Research in Cardiovascular Disease scientific meeting in Washington DC, May 19–21, 2010.