Background: Off-label dosing of direct oral anticoagulants (DOACs) is encountered clinically among patients with atrial fibrillation (AF), although data on the clinical outcomes of over- and under-dosing are lacking in Japan. Methods and Results: We examined the clinical outcomes of off-label DOAC dosing using the SAKURA AF Registry, a prospective multicenter registry in Japan. Among 3,237 enrollees, 1,676 under any of the 4 DOAC regimens were followed up for a median of 39.3 months: 746 (45.0%), appropriate standard-dose; 477 (28.7%), appropriate low-dose; 66 (4.0%), over-dose; and 369 (22.2%) under-dose. Compared with the standard-dose group, patients in the under- and over-dose groups were significantly older and had a higher stroke risk. After multivariate adjustment, stroke/systemic embolism (SE) and death events were equivalent between the standard- and under-dose groups, but major bleeding events tended to be lower in the under-dose group (hazard ratio [HR] 0.474, P=0.0739). Composite events (stroke/SE, major bleeding, or death) were higher in the over-dose than in the standard-dose group (HR 2.714, P=0.0081).
Conclusions: Clinical outcomes were not worse for under-dose than for standard-dose users among patients with different backgrounds. Over-dose users, however, were at higher risk for all clinical events and required careful follow-up. Further studies are needed to clarify the safety and effectiveness of off-label DOAC dosing in Japan.
Keywords: Atrial fibrillation; Direct oral anticoagulants; Off-label dose therapy.