Abstract P60: The Effect of Angiotensin Receptor Blocker/Calcium Channel Blocker Single Pill Combination Therapy on Adherence to Antihypertensive Treatment

Abstract

Objective: To evaluate the impact of ARB/CCB single pill combination therapy on adherence to antihypertensive (AHY) treatment. 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, age ≥18 years, and continuously enrolled in the same health plan for 6 months prior to and 13 months after starting ARB/CCB treatment. Patients who started either valsartan and amlodipine or amlodipine and olmesartan medoxomil ARB/CCB single pill combinations were assigned to the single pill combination (SPC) group. The ARB/CCB free combination (FC) group included patients who used a combination of single-agent ARB and 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 weighted multivariable regression models were used to estimate the impact of combination pill therapy. Covariates included age, gender, baseline comorbidities, insurance type, geographic region, copayment, and history of other AHY use. Results: The final sample contained 2,312 patients in the ARB/CCB FC group and 2,213 patients in the ARB/CCB SPC group. After adjustment for differences in baseline characteristics, a Cox proportional hazards model showed that patients in the SPC group were 24% less likely to discontinue ARB/CCB therapy as compared to patients in the FC group (HR 0.76, 95% CI 0.73-0.79, p<0.0001). A logistic model showed that patients in the SPC pill group had a 90% greater odds of being adherent compared to patients in the FC group (OR 1.90, 95% CI 1.75-2.08, p<0.0001). In both models, higher copayment (copayment $50 and above) was associated with poorer persistence and adherence in comparison to patients who faced copayment $0-$5: HR=1.15, p<0.001 and OR=0.67, p<0.0001. Conclusion: Patients using single pill combination ARB/CCB therapy were more likely to be persistent and adherent to treatment as compared to patients taking free combination therapy.