Medication adherence among community-dwelling patients with heart failure

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.