Moderate
Established
説明
Regular or high-dose acetaminophen can potentiate the anticoagulant effect of warfarin, leading to INR elevation and increased bleeding risk, even though single analgesic doses carry a lower risk.
機序
Acetaminophen inhibits CYP2C9-mediated warfarin metabolism and may reduce hepatic synthesis of vitamin K-dependent clotting factors through a NAPQI-mediated mechanism; the effect is dose-dependent.
臨床的意義
Pharmacokinetic studies and case reports demonstrate clinically significant INR increases with acetaminophen doses exceeding 2 g/day over several days.
対処法
Limit acetaminophen to the lowest effective dose and duration; monitor INR more frequently when starting or stopping regular acetaminophen use; counsel patients to report unusual bruising or bleeding.