Aim: Edoxaban is a non-vitamin K antagonist oral anticoagulant (NOAC) widely used for long-term stroke prevention in patients with non-valvular atrial fibrillation (NVAF). Adherence to NOACs is unsatisfactory and decreases over time. The aim of this study was to explore appropriated remedial dosing regimens for non-adherent edoxaban-treated NVAF patients through the Monte Carlo simulation. Methods: Six proposed regimens were compared with the recommendations in the European Heart Rhythm Association (EHRA) guide regarding the trough total deviation time considering both edoxaban plasma concentration and inactive factor Xa activity. Monte Carlo simulations were performed using RxODE based on the published population pharmacokinetics/pharmacodynamics model. Results: The proposed remedial strategies were different from EHRA recommendations and were related to delay duration. The missed dose can be taken immediately if the delay time is within 11 h. When the delay period is between 12 and 19 h, a half dose followed by a regular dosing schedule is recommended. When the delay time exceeds 19 h, a full dose followed by a half dose is preferred compared to that recommended in the EHRA guide. Our proposed strategies resulted in a shorter total deviation time than EHRA guide. Conclusion: PK/PD modelling and simulation are effective in developing and evaluating the remedial strategies of edoxaban, which could help maximize its therapeutic effect.

Background: Rivaroxaban is an oral anticoagulant used widely for stroke prevention in patients with non-valvular atrial fibrillation (NVAF). During long-term anticoagulant therapy, delayed or missed doses are common. However, a lack of practical instructions on remedial methods has created a barrier to maximise the benefit of the medications. This study aimed to explore appropriate remedial dosing regimens for non-adherent rivaroxaban-treated patients. Methods: Monte Carlo simulation based on a previously established rivaroxaban population pharmacokinetic/pharmacodynamic (PK/PD) model for patients with NVAF was employed to design remedial dosing regimens. The proposed regimens were compared with remedial strategies in the European Heart Rhythm Association (EHRA) guide by assessing deviation time in terms of drug concentration, factor Xa activity, and prothrombin time under various scenarios of non-adherence. Results: The proposed remedial dosing regimens were dependent on delay duration. The missed dose should be taken immediately when the delay does not exceed 6 h; a half dose is advisable when the delay is between 6-20 h. A missed dose should be skipped if less than 4 h remains before the next dose. Age or renal function does not significantly influence remedial dosing regimens. The proposed regimens resulted in shorter deviation time than that of the EHRA guide in most non-adherence scenarios. Conclusion: EHRA guide may not provide optimal remedial strategies for rivaroxaban-treated non-adherent patients based on simulation. PK/PD and simulation provide valid evidence on the remedial dosing regimen of rivaroxaban for patients with NVAF, which could help to minimise the risk of bleeding and thromboembolism.