Letter by Suwa et al Regarding Article, “Safety of Switching From a Vitamin K Antagonist to a Non–Vitamin K Antagonist Oral Anticoagulant in Frail Older Patients With Atrial Fibrillation: Results of the FRAIL-AF Randomized Controlled Trial”

Abstract

al 1 recently demonstrated that switching from international normalized ratio-guided vitamin K antagonist (VKA) to non-VKA oral anticoagulant (NOAC) treatment in frail older patients with atrial fibrillation provokes more bleeding events compared with continuing VKA. However, international normalized ratio-guided VKA and nonmonitored NOAC treatment mainly used rivaroxaban, without clarification of the dose adjustment; therefore, this is an inadequate comparative study. In addition, although the authors show that the incidence of bleeding events was somewhat different (higher in rivaroxaban and apixaban and lower in edoxaban) in Figure 3, illustrating the subgroup analyses, they do not comment on the reason that the prescription of NOAC was nonrandomized. Each NOAC has clear differences in drug effects, especially concerning safety. We indicated that rivaroxaban had a high incidence of bleeding events, and plasma concentration in peak samplings measured with anti-FXa chromogenic assay showed higher levels in rivaroxaban compared with edoxaban dosing. 2 We had the same results when switching from rivaroxaban to edoxaban in the same patients, including elderly participants. 2 As mentioned previously, plasma concentration-directed dose adjustment has been shown to be helpful in controlling outcomes and prevented unnecessary bleeding events in NOAC dosing, even off-label dosing. 2,3 When using oral anticoagulants, many bleeding and thromboembolic events occurred. If