The real world use of combined P-glycoprotein and moderate CYP3A4 inhibitors with rivaroxaban or apixaban increases bleeding.

The use of direct oral anticoagulants for stroke prevention in atrial fibrillation continues to rise. Certain populations may be at higher risk for increased drug exposure and adverse events. Pharmacokinetic studies suggest increased exposure of rivaroxaban and apixaban with combined P-gp and moderate CYP3A4 inhibitors but the clinical relevance of this is unknown. This retrospective cohort study included patients receiving rivaroxaban or apixaban from January 1, 2012 to December 31, 2016 with a moderate inhibitor (amiodarone, dronedarone, diltiazem, verapamil) for at least 3 months in the drug-drug interaction (DDI) group. Propensity matching was used to identify similar control patients without the presence of the DDI. The primary outcome was a time to event analysis of any bleeding episode as defined by the International Society of Thrombosis and Hemostasis. After propensity matching, 213 patients with similar baseline characteristics were included in each group. The mean CHA2DS2-VASc score was 3.0 and median duration of follow-up was 1.45 years. The primary outcome occurred in 26.4% of patients in the DDI group and 18.4% in the control group (hazard ratio 1.8, 95% confidence interval [CI] 1.19 to 2.73; p-value = 0.006). There was no difference in bleeding rates based on type of inhibitor. Use of a combined P-gp and moderate CYP3A4 inhibitor with rivaroxaban or apixaban increased bleeding risk compared to patients without the DDI in this real world, retrospective study. Analysis in a larger patient population is needed to confirm these findings.