ModerateMacrolides×Vitamin K antagonist anticoagulants
Updated · Methodology
Mechanism
Azithromycin suppresses vitamin K-producing gut flora, raising INR. Bleeding cases have been reported.
Symptoms
Gum bleeding, epistaxis, bruising without trauma, black or tarry stools. Higher risk in older patients and prior peptic ulcer disease.
Management
For short azithromycin courses (3–5 days), check INR 3–5 days after start and 5 days after stopping the antibiotic. If INR rises above target, reduce warfarin by 10–20%. Alternative antibiotics: a cephalosporin (minimal gut flora effect).
Check the full regimen, not just this pair
Opens the checker with these two drugs prefilled. Add the rest of the regimen and recompute additive risks.
Summary of a multi-drug list →
Medicine list: everything you take in one place →
Sources
- FDA: Zithromax (azithromycin) prescribing information (2013)– ; DailyMed setid db52b91e-79f7-4cc1-9564-f2eee8e31c45
- AEMPS: Ficha técnica: Azitromicina (nº registro 66065), sección 4.5 (2026)– AEMPS, CIMA, nº registro 66065, revisión 04/2026, sección 4.5