Medication adherence among community-dwelling patients with heart failure

Abstract

Objective: To determine medication use and adherence among community-dwelling patients with heart failure (HF).

Patients and methods: Residents of Olmsted County, Minnesota, with HF were recruited from October 10, 2007, through February 25, 2009. Pharmacy records were obtained for the 6 months after enrollment. Medication adherence was measured by the proportion of days covered (PDC). A PDC of less than 80% was classified as poor adherence. Factors associated with medication adherence were investigated.

Results: Among the 209 study patients with HF, 123 (59%) were male, and the mean ± SD age was 73.7 ± 13.5 years. The median (interquartile range) number of unique medications filled during the 6-month study period was 11 (8-17). Patients with a documented medication allergy were excluded from eligibility for medication use within that medication class. Most patients received conventional HF therapy: 70% (147/209) were treated with β-blockers and 75% (149/200) with angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers. Most patients (62%; 127/205) also took statins. After exclusion of patients with missing dosage information, the proportion of those with poor adherence was 19% (27/140), 19% (28/144), and 13% (16/121) for β-blockers, angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers, and statins, respectively. Self-reported data indicated that those with poor adherence experienced more cost-related medication issues. For example, those who adhered poorly to statin therapy more frequently reported stopping a prescription because of cost than those with good adherence (46% vs 6%; P < .001), skipping doses to save money (23% vs 3%; P = .03), and not filling a new prescription because of cost (46% vs 6%; P < .001).

Conclusion: Community-dwelling patients with HF take a large number of medications. Medication adherence was suboptimal in many patients, often because of cost.

FIGURE 1.

Questionnaire administered to study patients.

FIGURE 2.

Proportion of patients filling prescriptions, categorized by the number of unique medications.

FIGURE 3.

Pharmacy-based medication adherence. The proportion of patients with poor medication adherence (PDC <80%) for each medication class are shown. Adherence was not calculated for loop diuretics because of frequent dosing changes. ACEI = angiotensin-converting enzyme inhibitor; ARB = angiotensin II receptor blocker; PDC = proportion of days covered.