Drug interactions
azithromycin + 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
Azithromycin may increase warfarin’s anticoagulant effect, raising INR and bleeding risk during and shortly after therapy.
Mechanism of action
Reduction of vitamin K–producing gut flora and possible inhibition of R-warfarin metabolism (CYP3A4) leading to increased anticoagulant effect; variable magnitude.
Clinical management
Monitor INR more frequently: check within 3–5 days of starting azithromycin and again after completion; adjust warfarin dose as needed. Consider earlier/more frequent checks if high bleeding risk; counsel on bleeding signs.
Drug reference
References
- ZITHROMAX (azithromycin) Prescribing Information — FDA Label
- COUMADIN (warfarin sodium) Prescribing Information — FDA Label
Frequently asked questions
Can I take azithromycin with warfarin?
The interaction is rated: Moderate. Azithromycin may increase warfarin’s anticoagulant effect, raising INR and bleeding risk during and shortly after therapy.
How serious is the interaction between azithromycin and warfarin?
The interaction is rated: Moderate. Evidence level: High.
How is the interaction between azithromycin and warfarin managed?
Monitor INR more frequently: check within 3–5 days of starting azithromycin and again after completion; adjust warfarin dose as needed. Consider earlier/more frequent checks if high bleeding risk; counsel on bleeding signs.
Why do azithromycin and warfarin interact?
Reduction of vitamin K–producing gut flora and possible inhibition of R-warfarin metabolism (CYP3A4) leading to increased anticoagulant effect; variable magnitude.
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