Fluvastatin and Warfarin: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Warfarin
Fluvastatin
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
What happens
Increased warfarin exposure, increased INR, and an increased risk of bleeding
Interaction Deep Dive
Coadministration of fluvastatin (CYP2C9 inhibitor) with warfarin (CYP2C9 substrate) may increase warfarin exposure, and may also increase INR. Consider CYP2C9 inhibition potential when starting, stopping, or changing the dose of concomitant medications2. There are postmarketing reports of clinically evident bleeding and/or increased INR in patients taking concomitant statins and warfarin. Obtain an INR before starting fluvastatin in patients taking warfarin and frequently enough after initiation or discontinuation to ensure that no significant alteration in INR occurs. Once the INR is stable, monitor INR at regularly recommended intervals 1. Statin therapy in combination with warfarin is beneficial when clinically indicated with appropriate monitoring 3.
Why it happens (mechanism)
Inhibition of CYP2C9-mediated metabolism of warfarin
Literature reports
4 reports — tap to read
a) Coadministration of vitamin K antagonists (VKAs) with statin therapy was associated with a minor increase in anticoagulant effect of VKAs in a systematic review of 8 studies. Warfarin was the most commonly used VKA and simvastatin was the most commonly used statin within the studies. In patients receiving warfarin, initiation of simvastatin increased INR by 0.15 to 0.65. A similar effect of slightly increased anticoagulation (increased INR, reduced VKA doses, and increased risk of hospitalization for gastrointestinal bleeds) also occurred with other statins, including atorvastatin, rosuvastatin, and fluvastatin. Studies including pravastatin did not report an effect on anticoagulation. Due to significant heterogeneity between studies, a direct comparison by meta-analysis was not feasible 4.
b) Supratherapeutic elevation of the INR occurred in a 67-year-old male patient receiving concomitant therapy with warfarin and fluvastatin. Maintained on a stable regimen of warfarin 4 mg daily for over 5 months (target INR, 2 to 3), the patient had received concomitant therapy with atorvastatin 20 mg daily while on warfarin, without incident. Nine weeks after converting to fluvastatin 80 mg/day (extended release formulation), his INR measured at 6.6. The patient denied episodes of bruising or bleeding, and had not changed his warfarin regimen. He was converted back to atorvastatin, warfarin was discontinued for 4 days and then dose-adjusted 1 week later, and within 4 weeks, his INR returned to within target range 5.
c) When a 68-year-old female patient on warfarin (42.5 mg per week) was given fluvastatin 20 mg daily, the INR increased to 4.17 after 2 weeks of fluvastatin therapy. Reduction of the warfarin dose was required to achieve a therapeutic INR (range, 2.5 to 3.5). Fluvastatin was discontinued after 2 months secondary to insomnia. An 83-year-old female patient was stabilized on warfarin 22 mg per week with resulting INRs of 1.84 to 2.73. Fluvastatin 20 mg daily was added to therapy, and the INR increased to 3.47 in 1 week. The warfarin dose was decreased to 14 mg per week, and the INR decreased to 1.67. However, the patient discontinued fluvastatin therapy due to dizziness, and the warfarin dose was increased to its pre-fluvastatin levels, with the subsequent INRs returning to the therapeutic range. The third patient, a 51-year-old male, received warfarin 60 mg per week, resulting in INRs of 1.95 to 3.4. After 1 week of fluvastatin therapy at 20 mg daily, the patient reported rectal bleeding, and the INR was 4.2. When warfarin was decreased to 52.5 mg weekly, the INR dropped to 3.2 within 6 days. Four months later, the patient continued on fluvastatin therapy, and the INRs remained in the therapeutic range 6.
d) There are postmarketing reports of clinically evident bleeding and/or increased INR in patients taking concomitant statins and warfarin. In the drug-interaction studies, coadministration of 40 mg once daily fluvastatin for 8 days with 30 mg once daily warfarin, increased the AUC and Cmax of S-warfarin by 7% and 10% respectively and Cmax of R-warfarin by 6%. The AUC and Cmax of fluvastatin increased by 30% and 67% respectively. However, the findings are clinically not significant 1.
Common questions
Can I take Fluvastatin and Warfarin together?
Increased warfarin exposure, increased INR, and an increased risk of bleeding Always confirm with your pharmacist or prescriber before making any change.
How serious is the Fluvastatin and Warfarin interaction?
It is rated moderate. Can be significant — usually manageable with monitoring.
How quickly could this interaction happen?
The documented onset is "delayed". Effects tend to build up gradually over days to weeks.
How strong is the evidence for this interaction?
The evidence is graded "established". Well documented — supported by controlled studies or strong clinical data.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Fluvastatin or Warfarin need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there anything you'd monitor while I'm on both?
References (6)
- Product Information: Lescol(R) XL oral extended release tablets, fluvastatin sodium oral extended release tablets. Sandoz, Inc.(per FDA), Princeton, NJ, 2023. DailyMed
- Product Information: WARFARIN SODIUM oral tablets, warfarin sodium oral tablets. Teva Pharmaceuticals (per Dailymed), Parsippany, NJ, 2023. DailyMed
- Wiggins BS, Saseen JJ, Page RL, et al: Recommendations for management of clinically significant drug-drug interactions with statins and select agents used in patients with cardiovascular disease: a scientific statement from the American Heart Association. Circulation 2016; 134(21):e468-e495. PubMed
- Engell AE, Svendsen ALO, Lind BS, et al: Drug-drug interactions between vitamin K antagonists and statins: a systematic review. Eur J Clin Pharmacol 2021; 77(10):1435-1441. DOI
- Andrus MR: Oral anticoagulant drug interactions with statins: case report of fluvastatin and review of the literature. Pharmacotherapy 2004; 24:285-290. PubMed
- Kline SS & Harrell CC: Potential warfarin-fluvastatin interaction (letter). Ann Pharmacother 1997; 31:790. DOI
Keep reading about Warfarin
Keep reading about Fluvastatin
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