Drug-drug interaction between warfarin and statins: A Danish cohort study

Anna E. Engell*, Andreas L.O. Svendsen, Bent S. Lind, Christen L. Andersen, John S. Andersen, Tora G. Willadsen, Frederik Persson, Anton Pottegård

*Corresponding author for this work

    Research output: Contribution to journalJournal articleResearchpeer-review

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    Initiation of statin treatment is suggested to increase the international normalised ratio (INR) among warfarin users. However, available data is limited and conflicting. We conducted a register-based cohort study to evaluate the drug-drug interaction between warfarin and statins. By linking data on INR measurements and filled prescriptions, we identified warfarin users 2000-2015 initiating simvastatin (n = 1363), atorvastatin (n = 165) or rosuvastatin (n = 23). Simvastatin initiation led to an increase in mean INR from 2.40 to 2.71, with INRs peaking after 4 weeks, corresponding to a mean change of 0.32 (95%CI 0.25-0.38). High-dose and low-dose simvastatin led to comparable changes (mean change 0.33 vs 0.29). Initiation of atorvastatin and rosuvastatin lead to INR increases of 0.27 (95%CI 0.12-0.42) and 0.30 (95%CI -0.09-0.69). In conclusion, initiation of simvastatin, atorvastatin or rosuvastatin among warfarin users led to a minor increase in INR. The magnitude of this change is for most patients likely of limited clinical relevance.

    Original languageEnglish
    JournalBritish Journal of Clinical Pharmacology
    Issue number2
    Pages (from-to)694-699
    Publication statusPublished - Feb 2021


    • anticoagulants and warfarin
    • drug interactions
    • statins


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