Abstract 62: Impact of Once-Daily vs. Twice-Daily Dosing Frequency on Adherence in Chronic Medications among Patients with Non-Valvular Atrial Fibrillation

Abstract

Objective: Multiple daily dosing may be negatively associated with patient medication adherence, but the findings are inconclusive. This study aims at comparing adherence to chronic medications for once-daily (QD) vs. twice-daily (BID) dosing in patients with non-valvular atrial fibrillation (NVAF). Methods: We analyzed the PharMetrics Integrated Claims database from 2004 to 2009. Adult patients with continuous insurance coverage, newly initiated on a QD or BID diabetes or hypertension medication, and having at least 1 AF diagnosis (ICD-9 427.31) were included. Patients with observed valvular heart disease or valve replacement procedures during the 180 days before the index fill date were excluded. The observation period started on the index date until the earliest of switching to another drug class, health plan disenrollment, and end of data availability. Compliance was calculated in two ways: medication possession ratio (MPR) and proportion of days covered (PDC). Adherence was defined as a MPR or PDC ≥ 0.8. Multivariate logistic regressions were conducted to compare the probability of adherence, adjusting for baseline demographics, index medications, comorbidities, pills burden, and healthcare costs. Results: Total of 8,256 QD and 2,441 BID patients with NVAF initiating the target chronic medications were identified. For the QD and BID group respectively, means (SD) age were 57.3 (14.0) and 56.9 (13.8) years (p=NS); 34% and 33% were females (p=NS); means (SD) duration of exposure to therapy were 447 (400) and 406 (374) days (p<.001). Based on MPR, 75% of QD patients compared to 70% of BID patients were adherent (p<.001). For PDC at 3, 6, 12 and 18 months, the proportions of adherent patients for the QD and BID groups were 74% vs. 68%, 65% vs. 58%, 57% vs. 50%, and 51% vs. 44% (p<.001 for all comparisons), respectively. The adjusted odds ratio (95% CI) of adherence for the QD relative to BID group was 1.22 (1.09 - 1.36) based on MPR and 1.23 (1.07 - 1.41) based on PDC at 12 months. Conclusions: This study demonstrates that NVAF patients treated with QD dosing regimens for chronic medications were associated with approximately a 22% higher likelihood of adherence than those on BID regimens, regardless of whether Medication Possession Ratio or Proportion of Days Covered was used to define compliance.