MAJOR — Use With Caution
FDA-documented major interaction. INR can increase 2-3 fold. Warfarin dose reduction of 25-50% typically needed. Frequent INR monitoring required.
Evidence level: STRONG
Fluconazole (Diflucan, an antifungal) dramatically increases the blood-thinning effect of warfarin by blocking the enzyme that removes warfarin from your body. This can cause dangerous, even life-threatening bleeding.
Fluconazole is a strong CYP2C9 inhibitor. Warfarin S-enantiomer (more potent) is metabolized by CYP2C9. Fluconazole dramatically increases warfarin levels and anticoagulant effect. FDA label for both drugs documents this interaction.
If you take warfarin and need fluconazole, your doctor should reduce your warfarin dose and check your INR (blood clotting test) frequently. Even a single dose of fluconazole can significantly increase bleeding risk.
Take Warfarin at the same time each day (evening is common for warfarin). Fluconazole follows its prescribed schedule. Many medications can affect anticoagulant levels — always inform your pharmacist before starting anything new.
Higher risk with: older age (65+), history of GI bleeding, concurrent use of multiple blood-thinning agents, liver disease, heavy alcohol use, recent surgery.
Unusual bruising, blood in urine or stool, nosebleeds that won't stop, bleeding gums, black tarry stools, vomiting blood, severe headache (possible brain bleed)
Request INR check within 3-5 days of starting fluconazole. Discuss preemptive warfarin dose reduction (typically 25-50%). Consider alternative antifungals if possible.
This medication combination requires careful medical oversight. Your doctor or anticoagulation clinic can adjust doses or select alternatives with fewer bleeding risks. Frequent INR monitoring is essential.
Fluconazole (Diflucan, an antifungal) dramatically increases the blood-thinning effect of warfarin by blocking the enzyme that removes warfarin from your body. This can cause dangerous, even life-threatening bleeding.
Take Warfarin at the same time each day (evening is common for warfarin). Fluconazole follows its prescribed schedule. Many medications can affect anticoagulant levels — always inform your pharmacist before starting anything new.
Unusual bruising, blood in urine or stool, nosebleeds that won't stop, bleeding gums, black tarry stools, vomiting blood, severe headache (possible brain bleed)
This medication combination requires careful medical oversight. Your doctor or anticoagulation clinic can adjust doses or select alternatives with fewer bleeding risks. Frequent INR monitoring is essential.
Request INR check within 3-5 days of starting fluconazole. Discuss preemptive warfarin dose reduction (typically 25-50%). Consider alternative antifungals if possible.
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