Major
Established
説明
Concurrent use significantly increases bleeding risk through dual anticoagulant/antiplatelet mechanisms. Even low-dose aspirin (81 mg) meaningfully raises the risk of major hemorrhage.
機序
Aspirin irreversibly inhibits COX-1-mediated thromboxane A2 synthesis, impairing platelet aggregation; additionally, aspirin may displace warfarin from plasma proteins and inhibit hepatic CYP2C9, increasing warfarin exposure.
臨床的意義
Meta-analyses demonstrate a 2- to 3-fold increase in major bleeding events when aspirin is added to warfarin therapy.
対処法
Avoid combination unless clearly indicated (e.g., mechanical heart valves). If combined, use the lowest effective aspirin dose, tighten INR monitoring, and add gastroprotection (PPI).