Moderate
Probable
Description
Simvastatin modestly potentiates warfarin anticoagulation, leading to small but potentially clinically relevant INR increases.
Mechanism
Simvastatin may inhibit CYP2C9-mediated S-warfarin metabolism; the precise mechanism is not fully elucidated but has been observed across multiple statins.
Clinical Significance
INR increases of ~10–20% have been observed; dose-dependent effect—higher simvastatin doses carry greater risk.
Management
Monitor INR when starting, stopping, or changing the simvastatin dose; adjust warfarin if INR moves outside target range.