The effect of simvastatin on warfarin anticoagulation: a Swedish register-based nationwide cohort study

Purpose Some data indicate that simvastatin may increase the anticoagulative effect in patients treated with warfarin, but the evidence is scarce. The aim of the present study was to investigate how the anticoagulative effect of warfarin is affected by the initiation of simvastatin in a very large p...

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Bibliographic Details
Published in:European journal of clinical pharmacology 2019-10, Vol.75 (10), p.1387-1392
Main Authors: Andersson, Marine L., Mannheimer, Buster, Lindh, Jonatan D.
Format: Article
Language:English
Subjects:
Adolescent
Adult
Aged
Aged, 80 and over
Anticoagulants
Anticoagulants - pharmacology
Biomedical and Life Sciences
Biomedicine
Blood Coagulation - drug effects
Cohort analysis
Drug Interactions
Female
Humans
Hydroxymethylglutaryl-CoA Reductase Inhibitors - pharmacology
International Normalized Ratio
Male
Medicin och hälsovetenskap
Middle Aged
Pharmacokinetics and Disposition
Pharmacology/Toxicology
Retrospective Studies
Simvastatin
Simvastatin - pharmacology
Sweden
Warfarin
Warfarin - pharmacology
Young Adult
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Summary:Purpose Some data indicate that simvastatin may increase the anticoagulative effect in patients treated with warfarin, but the evidence is scarce. The aim of the present study was to investigate how the anticoagulative effect of warfarin is affected by the initiation of simvastatin in a very large patient sample. Methods In a retrospective cohort study, we included 5637 individuals on warfarin treatment initiating simvastatin. INR values and warfarin doses were calculated week-by-week during co-treatment. Data were obtained from two large Swedish warfarin registers and from the Swedish Prescribed Drug Register. Results INR increased from 2.43 at baseline to 2.58, 4 weeks after simvastatin initiation, and did not stabilize until the last quarter of the year studied. Consequently, the proportion of patients with an INR above 3 increased from around 8 to 15%. Conclusions In conclusion, initiation of simvastatin resulted in moderately increased INR values and subsequent dose decreases in patients already on warfarin. In order to avoid the increased risk of bleeding, the initiation of simvastatin may be accompanied by closer INR monitoring.
ISSN:0031-6970
1432-1041
1432-1041
DOI:10.1007/s00228-019-02703-3