Abstract
ObjectiveIn this study, we aimed to assess the utilization pattern (potentially inappropriate dosing and concomitant use of contraindicated drugs) and adherence to direct oral anticoagulants (DOACs), including apixaban, dabigatran, and rivaroxaban, in patients with atrial fibrillation (AF) unsuitable for warfarin.MethodsWe used nationally representative data, namely Health Insurance Review and Assessment Service-Aged Patient Sample 2014, that included medical and pharmacy claims of approximately 1 million patients aged 65 or older. We included patients who had at least one diagnosis of AF and at least one prescription of DOAC between January 1 and December 31, 2014. In 2014, DOACs were reimbursed only to patients with AF unsuitable for warfarin. Appropriate dosing and contraindicated drugs were determined according to the Summary of Product Characteristics for each DOAC. Multivariate logistic regression was performed to examine the factors contributing to the concomitant use of contraindicated drugs. To assess adherence, we calculated the medication possession ratio (MPR).ResultsThe percentage of inappropriate dosing was 11.8% among 1,234 patients with AF; it was the highest in rivaroxaban users (16.8%). Contraindicated drugs were prescribed to 236 patients (19.1%). Clinics, smaller healthcare institutions, and outpatient visits were significantly related to contraindicated drug use. The mean MPRs were 0.95, 0.93, and 0.91 for apixaban, dabigatran, and rivaroxaban, respectively (P = 0.075).ConclusionsCareful monitoring is warranted in patients with AF aged over 65 who were unsuitable for warfarin to reduce the incidence of inappropriate dosing and concomitant use of contraindicated drugs.
Highlights
Atrial fibrillation (AF) is one of the risk factors of stroke, where 15–20% of stroke events are related to atrial fibrillation (AF) [1, 2]
Careful monitoring is warranted in patients with AF aged over 65 who were unsuitable for warfarin to reduce the incidence of inappropriate dosing and concomitant use of contraindicated drugs
The majority of patients were treated with dabigatran (48.1%), followed by rivaroxaban (43.4%) and apixaban (8.6%)
Summary
Atrial fibrillation (AF) is one of the risk factors of stroke, where 15–20% of stroke events are related to AF [1, 2]. Older patients with AF constitute almost half of all patients with AF and are known to have increased risk of stroke and bleeding [3]. As a previous study reported, doses of oral anticoagulants (OACs), concomitant drugs, comorbidities, and adherence largely affect the anticoagulant effect of OACs in older patients with AF [3]. Warfarin has been widely used for prevention of stroke in patients with AF. Based on the results of several clinical trials, direct oral anticoagulants (DOACs) were approved for the same purpose [4,5,6,7]. DOACs have fewer drug interactions and lower risk of intracranial hemorrhage. It does not require regular blood tests [8]
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