Moderate
Amoxicillin × Warfarin
Penicillins with extended spectrum×Vitamin K antagonist anticoagulants
Mechanism
Amoxicillin may reduce gut flora vitamin K synthesis – INR mildly rises. Effect usually moderate.
Symptoms
INR above target, occasional bleeding.
Management
Check INR on day 5 if course longer than 5 days.
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.
Sources
- Lexicomp: Lexicomp Drug Interactions (2024)– Wolters Kluwer Clinical Drug Information, Inc. Lexi-Interact Online, 2024
- Pharmaceutical Press: Stockley's Drug Interactions, 12th edition (2024)– Preston CL (ed.). Stockley's Drug Interactions. 12th ed. London: Pharmaceutical Press; 2024
- DailyMed: Warfarin: FDA prescribing information, Drug Interactions section (DailyMed) (2024)