Relationship Between Direct Oral Anticoagulant Doses and Clinical Outcomes in Elderly Patients With Non-Valvular Atrial Fibrillation - ANAFIE Registry Sub-Analysis

BACKGROUND

This sub-analysis of the ANAFIE Registry, a prospective, observational study of >30,000 Japanese non-valvular atrial fibrillation (NVAF) patients aged ≥75 years, assessed the prevalence of direct oral anticoagulant (DOAC) under-dose prevalence, identified the factors of under-dose prescriptions, and examined the relationship between DOAC dose and clinical outcomes.Methods and Results: Patients, divided into 5 groups by DOAC dose (standard, over-, reduced, under-, and off-label), were analyzed for background factors, cumulative incidences, and clinical outcome risk. Endpoints were stroke/systemic embolic events (SEE), major bleeding, and all-cause death during the 2-year follow-up. Of 18,497 patients taking DOACs, 20.7%, 3.8%, 51.6%, 19.6%, and 4.3%, were prescribed standard, over-, reduced, under-, and off-label doses. Factors associated with under-dose use were female sex, age ≥85 years, reduced creatinine clearance, history of major bleeding, polypharmacy, antiplatelet agents, heart failure, dementia, and no history of catheter ablation or cerebrovascular disease. After confounder adjustment, under-dose vs. standard dose was not associated with the incidence of stroke/SEE or major bleeding but was associated with a higher mortality rate. Patients receiving an off-label dose showed similar tendencies to those receiving an under-dose; that is, they showed the highest mortality rates for stroke/SEE, major bleeding, and all-cause death.

CONCLUSIONS

Inappropriate low DOAC doses (under- or off-label dose) were not associated with stroke/SEE or major bleeding but were associated with all-cause death.

Safety and Efficacy Re-Evaluation of Edoxaban and Rivaroxaban Dosing With Plasma Concentration Monitoring in Non-Valvular Atrial Fibrillation: With Observations of On-Label and Off-Label Dosing

Background: Off-label dosing of direct oral anticoagulants (DOAC) as a treatment for non-valvular atrial fibrillation (NVAF) is problematic. Here, we investigated the status of rivaroxaban and edoxaban dosing by monitoring plasma concentrations (PCs). Methods and Results: We monitored drug PCs in 391 and 333 outpatients receiving rivaroxaban and edoxaban, respectively, for NVAF. Drug doses were adjusted if the PC was above the cut-off value (rivaroxaban: 404 ng/mL; edoxaban: 402 ng/mL), determined from receiver operating characteristic curves for predicting bleeding events. On-label standard dosing was reduced to off-label underdosing due to high PCs above the cut-off more often for rivaroxaban (28.1%) than edoxaban (12.6%; P<0.001). Over a median follow-up of 13 months for rivaroxaban and 10 months for edoxaban, the annual incidence of bleeding events was higher with rivaroxaban than with edoxaban (4.88 vs. 3.73 patient-years; P<0.05), although no thromboembolic events occurred in either group. Furthermore, for patients with creatinine clearance >50 mL/min and body weight ≤60 kg, there was a greater incidence of bleeding events with rivaroxaban on-label 15 mg dosing than with edoxaban on-label 30 mg dosing (22.2% vs 2.9%; P<0.01). Conclusions: Monitoring the PCs of rivaroxaban and edoxaban in NVAF patients enables dose adjustments to reduce bleeding risk. The incidence of bleeding under drug PC monitoring was less in the edoxaban than rivaroxaban group.

Off-label use of reduced dose direct oral factor Xa inhibitors in subjects with atrial fibrillation: a review of clinical evidence

In real-world clinical practice, underdosing, i.e. off-label use of reduced doses (RDs), of oral factor Xa inhibitors (oFXaIs) is quite common in stroke prevention in non-valvular atrial fibrillation, possibly reflecting the hope to increase safety without reducing efficacy in selected patients. To assess whether this strategy is associated with some clinical benefit, we used a physician-centred approach to evaluate whether current evidence supports the hypothesis that a substantial proportion of underdosing may be voluntary rather than casual, whether and to what extent oFXaIs' dose rather than patients' characteristics are associated with bleeding events, and which are the safety and efficacy clinical implications of oFXaIs' underdosing. Our review found consistent evidence that underdosing is often an intentional strategy; however, available studies do not demonstrate a sizeable net clinical benefit of using off-label RD oFXaIs.

Rivaroxaban or Apixaban for Non-Valvular Atrial Fibrillation - Efficacy and Safety of Off-Label Under-Dosing According to Plasma Concentration

BACKGROUND

Practice-based investigations on direct oral anticoagulant (DOAC) treatment for non-valvular atrial fibrillation (NVAF) have shown that off-label under-dosing is increasingly becoming an issue. Here, we investigate the significance of drug monitoring to prevent undesirable under-dosing with DOAC. Methods and Results: In 255 outpatients with NVAF undergoing treatment with rivaroxaban or apixaban we estimated the cut-offs for bleeding events using drug plasma concentration (PC) data 3 h after drug treatment, that is, at the peak level. Furthermore, we evaluated the appropriateness of labeled and off-label dosing implemented for 348 patients using the obtainable PC threshold. A total of 73 off-label under-dose users of rivaroxaban (37% of all users and 63% of lower dose users) had acceptable peak PC (155-400 ng/mL). Additionally, 46 off-label under-dose users of apixaban (31% of all users and 55% of lower dose users) received appropriate doses according to peak PC threshold (90-386.4 ng/mL). These off-label under-dose users reported no bleeding or thromboembolic events during follow-up.

CONCLUSIONS

Anticoagulation monitoring enables personalized and appropriate off-label under-dosing in NVAF patients on rivaroxaban or apixaban through the measurement of peak PC during DOAC use.