Warfarin Interactions

492 known interactions for Warfarin. Click any interaction for the full evidence-based breakdown.

⚠️ Major (25)

Warfarin + Activated CharcoalDANGEROUS — loss of anticoagulation protection
Warfarin + AmiodaroneFDA-documented major interaction. Warfarin dose should be reduced by 33-50% when amiodarone is started. Effect persists months after amiodarone discontinuation due to 40-55 day half-life.
Warfarin + AspirinFDA-documented major interaction. Some patients require both (mechanical heart valves, recent stents), but the combination requires careful risk-benefit assessment and monitoring.
Warfarin + CarbamazepineFDA-documented interaction. Warfarin dose increase usually needed. INR monitoring essential when starting, stopping, or adjusting carbamazepine dose.
Warfarin + CBD Oil🔴 MAJOR — CBD significantly increases warfarin levels. Do NOT combine without close medical supervision and frequent INR monitoring.
Warfarin + CelecoxibFDA-documented interaction. Celecoxib CYP2C9 inhibition plus residual bleeding risk. Monitor INR closely. COX-2 selectivity does not eliminate the interaction.
Warfarin + CiprofloxacinFDA-documented interaction. INR monitoring recommended when starting or stopping ciprofloxacin in warfarin patients.
Warfarin + Clarithromycin🔴 AVOID — FDA-documented interaction. Clarithromycin increases warfarin levels via CYP3A4 inhibition. INR monitoring essential. Consider azithromycin as a safer macrolide alternative.
Warfarin + ClopidogrelFDA-documented interaction. Sometimes prescribed together intentionally (mechanical valve + stent) but bleeding risk is very high. Triple therapy (warfarin + clopidogrel + aspirin) is extremely high risk.
Warfarin + Dong QuaiDANGEROUS — additive anticoagulant/antiplatelet effect; significant bleeding risk
Warfarin + ErythromycinFDA-documented interaction. Monitor INR closely during erythromycin treatment.
Warfarin + FluconazoleFDA-documented major interaction. INR can increase 2-3 fold. Warfarin dose reduction of 25-50% typically needed. Frequent INR monitoring required.
Warfarin + FluvoxamineFDA-documented interaction. Fluvoxamine is the SSRI most likely to increase warfarin levels (strong CYP1A2 + moderate CYP2C9 inhibition). INR monitoring essential.
Warfarin + Ginkgo Biloba🔴 CAUTION — Major interaction between Ginkgo Biloba and Warfarin. Avoid unless under direct medical supervision.
Warfarin + IbuprofenFDA-documented interaction. Increased risk of serious GI bleeding. Avoid combination if possible. If NSAID needed, use lowest dose for shortest duration with GI protection.
Warfarin + LumbrokinaseLumbrokinase + Warfarin — MAJOR Bleeding Risk (Contraindicated)
Warfarin + MetronidazoleFDA-documented interaction. INR monitoring required. Warfarin dose reduction usually needed during metronidazole course.
Warfarin + NaproxenFDA-documented interaction. Avoid combination. Naproxen longer half-life means extended period of increased bleeding risk compared to shorter-acting NSAIDs.
Warfarin + NattokinaseNattokinase + Warfarin — MAJOR Bleeding Risk (Contraindicated)
Warfarin + PhenytoinFDA-documented bidirectional interaction. Monitor both INR and phenytoin levels when drugs are used together or when either is adjusted.
Warfarin + RifampinFDA-documented major interaction. Rifampin can reduce warfarin effectiveness by 50% or more. Warfarin dose increases of 2-5x may be needed. When rifampin is stopped, warfarin levels will rise dangerously.
Warfarin + SerrapeptaseSerrapeptase + Warfarin — MAJOR Bleeding Risk
Warfarin + St. Johns Wort🔴 CAUTION — Major interaction between St. Johns Wort and Warfarin. Avoid unless under direct medical supervision.
Warfarin + Trimethoprim-SulfamethoxazoleFDA-documented major interaction — one of the most clinically significant warfarin-drug interactions. INR can rise dramatically. Consider alternative antibiotics.
Warfarin + Vitamin K2🔴 CAUTION — Major interaction between Vitamin K2 and Warfarin. Avoid unless under direct medical supervision.

⚡ Moderate (24)

✅ Safe (443)