Major
Clarithromycin × Warfarin
Macrolide antibiotic×Vitamin K antagonist anticoagulants
Mechanism
Clarithromycin inhibits CYP3A4 and CYP2C9. INR rises 25-50%.
Symptoms
Gum and nose bleeding, petechiae, haematuria within 5-10 days.
Management
Check INR on days 3 and 7. Alternative – azithromycin (minimal INR 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.