Clinical significance of potential interaction between warfarin and statins is unclear. Our objective was to determine whether use of statins as a class or use of simvastatin modulates the rate of bleeding requiring hospitalization among new warfarin users. Using Finnish healthcare databases, we identified a cohort of 101,588 warfarin initiators between 1 January 2009 and 30 June 2012. By the end of 2012, these patients accumulated 92,695 person-years of exposure to warfarin-only and 60,253 years of exposure to warfarin-with-statin. The outcome was a composite of gastrointestinal, intracranial or other bleeding leading to hospitalization. A Poisson generalized estimating equation model was employed to estimate rate ratios (RR) and their 95% confidence intervals (CI) for exposure to warfarin-with-statin compared to warfarin-only and to allow multiple episodes per patient and time-dependent covariates. In multivariable models, we found no difference in the bleeding rate in association with exposure to any statin (multivariable-adjusted RR = 0.98, 95% CI 0.89-1.07) or to simvastatin (RR = 1.01, 95% CI 0.91-1.11) with warfarin compared to exposure to warfarin-only. We conclude that concomitant use of statins and warfarin was not associated with an increased rate of bleeding requiring hospitalization.
© 2018 Nordic Association for the Publication of BCPT (former Nordic Pharmacological Society).