Allopurinol and Warfarin interaction
Allopurinol and Warfarin: both prescribing labels describe an interaction that usually calls for monitoring, a dose change, or spacing the doses.
Usually manageable with monitoring or a dose change. Tell your pharmacist you take both.
What the FDA labels say
From the Allopurinol label · effective 2026-05-21
Assess INR frequently and adjust warfarin dosage accordingly when allopurinol is added to warfarin therapy.
Dicumarol Clinical Impact Allopurinol tablets prolongs the half-life of the anticoagulant, dicumarol.
Adjust the dosage of dicumarol accordingly when allopurinol tablet is added to anticoagulant therapy.
Warfarin Clinical Impact Allopurinol may inhibit the metabolism of warfarin, possibly enhancing its anticoagulant effect.
From the Warfarin (Warfarin Sodium) label · effective 2026-06-24
…fluvoxamine, metronidazole, miconazole, oxandrolone, sulfinpyrazone, tigecycline, voriconazole, zafirlukast aprepitant, bosentan, carbamazepine, phenobarbital, rifampin CYP1A2 acyclovir, allopurinol, caffeine, cimetidine, ciprofloxacin, disulfiram, enoxacin, famotidine, fluvoxamine, methoxsalen, mexiletine, norfloxacin, oral contraceptives, phenylpropanolamine, propafenone,…
Taking more than these two? Interactions stack. Check your whole list at once; it stays in your browser.
Open in the checkerNot medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.