RESUMO
Background: Nonadherence to direct oral anticoagulants to prevent stroke occurs in up to 40% of atrial fibrillation patients. Underlying reasons are poorly understood. Objectives: This study quantified patient-reported reasons for nonadherence and identified strategies to improve adherence. Methods: This is a cross-sectional survey of atrial fibrillation patients in 2 academic health systems who reported apixaban nonadherence. We examined patient-reported reasons for nonadherence and level of nonadherence (assessed by a validated 3-item adherence measure) using a multivariable logistic regression model. Results: Of 419 study patients, 41.5% were women. The mean age was 71.1 ± 10 years and mean CHA2DS2VASc score was 3.2 ± 1.6. About two-thirds had adherence scores ≥80 (mild nonadherence) and one-third scores <80 (poor adherence). In all groups, forgetfulness contributed to nonadherence. Attitudes/beliefs associated with adherence score <80 included: not believing apixaban was needed (odds ratio [OR]: 12.24 [95% CI: 2.25-66.47]); medication cost (OR: 3.97 [95% CI: 1.67-9.42]); and fear of severe bleeding (OR: 3.28 [95% CI: 1.20-8.96]). Strategies that patients with adherence scores <80 selected as helping "a great deal/a lot" to increase adherence included bloodwork to evaluate efficacy (56%), physician counseling about adherence (55%), and having a reversal agent (39%). Almost one-half of all patients did not disclose nonadherence to their providers. Conclusions: Patients may not disclose their nonadherence to prescribers, and attitudes related to apixaban nonadherence differ among patients with mild nonadherence versus poor adherence. While all patients may benefit from strategies to address forgetfulness, concerns related to the purpose of apixaban, cost, and bleeding risk may require special attention in those with poor adherence.
RESUMO
BACKGROUND: Direct-acting oral anticoagulants are first-line agents for prevention of stroke in patients with nonvalvular atrial fibrillation (NVAF), but data are limited for the oldest patients, and with reduced dosing. OBJECTIVES: To determine steady-state apixaban peak and trough concentrations during routine care of older adults with NVAF, compare concentrations to clinical trial concentrations, and explore factors associated with concentrations. METHODS: A cross-sectional study of medically stable older adults with NVAF (≥75 years or ≥70 years if Black) receiving apixaban. Peak (2-4.4 hours post-dose) and trough (before next dose) concentrations were determined by anti-Xa activity calibrated chromogenic assay. Patient characteristics associated with concentrations were determined by multivariate modeling. RESULTS: The median age of patients (n = 115) was 80 (interquartile range: 77-84) years. The cohort comprised 46 women and 69 men; of which 98 are White, 11 Black, and 6 Asian. With 5 mg twice daily per labelling (n = 88), peak concentrations were higher in women: 248 ± 105 vs 174 ± 67 ng/mL in men (P < 0.001) and exceeded expected 95% range in 6 of 30 vs 0 of 55 men (P = 0.002). With 2.5 mg twice daily per label (n = 11), concentrations were <5 mg twice daily (peak: 136 ± 87 vs 201 ± 90 ng/mL, P = 0.026; trough: 65 ± 28 vs 109 ± 56 ng/mL, P < 0.001), but not different than 2.5 mg twice daily without reduction criteria (n = 13; peak: 132 ± 88; trough: 65 ± 31 ng/mL). Covariates associated with concentrations included sex, number of daily medications, and creatinine clearance. CONCLUSIONS: Older women had higher than expected peak apixaban concentrations, and 2.5 mg twice daily produced lower concentrations than standard dosing. Factors not currently included in dosing recommendations affected concentrations. The impact of apixaban concentrations on outcomes needs evaluation.