BACKGROUND Direct oral anticoagulants (DOACs) are the cornerstone of thromboembolic prevention in patients with atrial fibrillation, venous thromboembolism, or other cardiovascular conditions. However, DOAC use is associated with an increased risk of bleeding, with gastrointestinal (GI) bleeding being the most common site of major bleeding. Proton pump inhibitors (PPIs) are reasonably used during combined antithrombotic therapy or based on individual bleeding risk; nonetheless, evidence supporting their benefit in patients receiving DOAC therapy remains limited.

METHODS The Gastrointestinal protection Using proton-pump inhibitor in pAtients who RequireD Oral AntiCoagulants (GUARD-OAC) trial is a prospective, multicenter, open-label, randomized controlled trial evaluating the GI protective effect of PPI coadministration with DOAC. Eligible participants are patients with cardio- or cerebrovascular disease requiring long-term anticoagulation (≥1 year), who are currently receiving or initiating DOAC therapy, and have a HAS-BLED score of ≥1. The primary outcome is a composite of upper GI clinical events, including bleeding, symptomatic gastroduodenal ulcer, persistent pain of presumed GI origin with underlying multiple erosive disease, obstruction, or perforation. The secondary outcomes are the individual components of the primary outcome, GI symptoms or signs, cardiovascular or all bleeding events, and all-cause mortality. Assuming a 40% relative risk reduction of the primary outcome in the PPI plus DOAC group compared to the DOAC alone group, a total of 3,846 patients will be enrolled and followed for one year. A Clinical Events Committee will adjudicate clinical outcomes and adverse events for causality and attribution, and an independent Data Safety Monitoring Board will oversee the study. The GUARD-OAC trial is funded by the Ministry of Health & Welfare, Republic of Korea.

CONCLUSIONS The GUARD-OAC trial is the first randomized controlled trial exploring the efficacy of PPI cotherapy in patients receiving DOACs, providing evidence that may inform future guidelines on GI protection in this population.

TRIAL REGISTRATION Clinical Research Information Service, Identifier KCT0006848.