Prescription Drug Spending and Medication Adherence Among Medicare Beneficiaries with Heart Failure

BACKGROUND: Evidence suggests that cost sharing adversely affects appropriate prescription drug use for chronic disorders. However, few studies have evaluated this effect in heart failure (HF), the most common cause of hospitalization in Medicare. OBJECTIVE: To determine whether spending on HF pharmacotherapy by Medicare Part D enrollees was associated with prescription refill adherence. METHODS: This correlational study used pooled data from the 2010-2012 Medicare Current Beneficiary Survey (MCBS). The analysis sample consisted of community-dwelling MCBS participants with self-reported HF and continuous Part D coverage during the year of participation. 3 drug classes were analyzed independently: beta-blockers, angiotensin-converting enzyme (ACE) inhibitors, and angiotensin II receptor blockers (ARBs). 1,448 weighted participant-year records (derived from 964 individuals) met the inclusion criteria, of which 846 (58%) were included for beta-blockers, 633 (44%) for ACE inhibitors, and 229 (16%) for ARBs. Spending was measured by average out-of-pocket payment for the relevant prescription, standardized to a 30-day supply, as a percentage of average monthly income. Adherence was measured by the medication possession ratio (MPR): total days supplied for all but the last refill divided by number of days between the first and last fills of the year. RESULTS: Accounting for sampling weights, the median (interquartile range) monthly income was $1,472 ($949-$2,466), and average percentage of monthly income spent on a 30-day medication supply was 0.22% for beta-blockers, 0.19% for ACE inhibitors, and 0.90% for ARB5. Mean MPR was 88.9% for beta-blockers, 88.5% for ACE inhibitors, and 90.4% for ARBs. Risk-adjusted models showed that percentage of income spent on a beta-blocker prescription was directly associated with odds of nonadherence (MPR < 80%), odds ratio =1.38, 95% CI =1.01-1.89, P=0.045, and inversely associated with beta-blocker MPR, B=-4.17, SE =1.23, P=0.001. No such association was observed for ACE inhibitors or ARB5. CONCLUSIONS: Price sensitivity was evident for beta-blockers but not for antiangiotensin drugs, despite very low out-of-pocket costs and high adherence. This study is relevant to value-based pricing of HF management drugs in Part D plans. Copyright (C) 2019, Academy of Managed Care Pharmacy. All rights reserved.