Drug interactions
clarithromycin + warfarin
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Overview
Clarithromycin can increase warfarin effect and INR, raising bleeding risk; numerous reports and label warnings.
Mechanism of action
CYP3A4 inhibition increases R-warfarin exposure; reduced vitamin K–producing gut flora further potentiates anticoagulation.
Clinical management
Avoid if possible or choose an alternative antibiotic. If used, check INR within 3 days of start, again during therapy, and after discontinuation; adjust warfarin dose to target INR and monitor for bleeding.
Drug reference
References
- Biaxin (clarithromycin) Prescribing Information — FDA Label
- Coumadin (warfarin sodium) Prescribing Information — FDA Label
- Warfarin–Clarithromycin interaction — Lexicomp
Frequently asked questions
Can I take clarithromycin with warfarin?
The interaction is rated: Major. Clarithromycin can increase warfarin effect and INR, raising bleeding risk; numerous reports and label warnings.
How serious is the interaction between clarithromycin and warfarin?
The interaction is rated: Major. Evidence level: High.
How is the interaction between clarithromycin and warfarin managed?
Avoid if possible or choose an alternative antibiotic. If used, check INR within 3 days of start, again during therapy, and after discontinuation; adjust warfarin dose to target INR and monitor for bleeding.
Why do clarithromycin and warfarin interact?
CYP3A4 inhibition increases R-warfarin exposure; reduced vitamin K–producing gut flora further potentiates anticoagulation.
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