Medication adherence and treatment persistence following switching from vitamin K antagonists to direct oral anticoagulants: a systematic review

Background Switching from vitamin K antagonists (VKAs) to direct oral anticoagulants (DOACs) has become increasingly common because of the limitations associated with VKA therapy. However, adherence and persistence after switching remain important determinants of treatment effectiveness. This systematic review evaluated adherence and persistence outcomes following switching from VKAs to DOACs and summarized the reported reasons for switching. Methods A systematic review was conducted in accordance with PRISMA guidelines. PubMed and Scopus were searched for studies published between January 2016 and April 2026 evaluating adherence or persistence following switching from VKAs to DOACs. Eligible studies included randomized and observational studies involving adult patients with atrial fibrillation, venous thromboembolism, or other indications requiring anticoagulation therapy. Data on study characteristics, adherence and persistence outcomes (including proportion of days covered, medication possession ratio, and discontinuation measures), and reasons for switching were extracted and synthesized narratively. Results Sixteen studies were included. Adherence was assessed using both objective refill-based measures and subjective patient-reported tools. Objective adherence rates were generally moderate to high, with the proportion of patients achieving proportion of days covered (PDC) ≥ 80% ranging from 76% to 97.5% across most studies. Studies using subjective patient-reported instruments, including MMAS-8, ACTS, and PACT-Q2, reported more variable adherence levels. Persistence rates ranged from 54% to 94%, although substantial variability in persistence definitions and follow-up duration limited direct comparison across studies. Poor international normalized ratio control and low time in therapeutic range were the most commonly reported reasons for switching from VKAs to DOACs. Conclusions Studies evaluating switching from VKAs to DOACs generally reported moderate-to-high objective adherence rates, although persistence outcomes and subjective adherence measures were more variable. Methodological heterogeneity across studies highlights the need for standardized evaluation approaches and continued adherence-support strategies after switching.