Assessment of Anti-Xa activity in patients receiving concomitant apixaban with strong p-glycoprotein inhibitors and statins

What is known and objectives Although the apixaban Food and Drug Administration (FDA) package insert recommends dose reduction in patients administered dual strong inhibitors of p-glycoprotein (P-gp) and cytochrome P-450 (CYP) 3A4, there are limited published data regarding potential drug-drug interactions between apixaban (Eliquis) and common p-glycoprotein (P-gp) and CYP3A4 inhibitors co-administered with statins. The aim of this study was to investigate the degree of elevation relative to apixaban serum peak and trough concentration after the co-administration of amiodarone, diltiazem and statins (atorvastatin, rosuvastatin and simvastatin). Methods Patients prescribed apixaban 5mg twice daily for at least one week were identified from the anticoagulation clinic database and contacted for potential enrolment. A total of 117 volunteers were enrolled with eight excluded due to discontinued use, resulting in 109 volunteers (44 females and 65 males delineated into age groups 40-64 and >= 65 years old) completing the observational study. Fifty-five volunteers were administered apixaban without the P-gp inhibitors amiodarone or diltiazem, with or without statins (atorvastatin, rosuvastatin and simvastatin). Fifty-four volunteers were administered apixaban with either amiodarone or diltiazem, with or without statins (atorvastatin, rosuvastatin or simvastatin). Peak and trough concentrations were assessed for each patient utilizing an apixaban anti-Xa assay. Results Of the combinations studied, the mean apixaban trough concentration upon co-administration of amiodarone without a statin was elevated compared to apixaban alone (experimental 156.83 +/- 79.59 ng/ml vs. control 104.09 +/- 44.56 ng/ml; p = 0.04). The co-administration of diltiazem and rosuvastatin, and the administration of amiodarone without a statin led to greater than 1.5-fold increase in apixaban concentrations (peak experimental 315.19 +/- 157.53 ng/ml vs control 207.6 +/- 83.38 ng/ml; p = 0.08 and trough experimental 182.03 +/- 95.93 ng/ml vs control 112.32 +/- 37.78 ng/ml; p = 0.17) suggesting the need to assess dose adjustment for patients per the FDA package insert. In addition, the aggregated mean peak (p = 0.0056) and trough (p = 0.0089) elevation of CYP3A4 experimental groups (atorvastatin and simvastatin) co-administered apixaban and diltiazem were statistically significant compared with the aggregated non-CYP3A4 control groups (no statin and rosuvastatin). What is new and conclusion Herein, we report novel data regarding peak and trough apixaban concentrations after concomitant administration of P-gp and CYP3A4 inhibitors (amiodarone or diltiazem) co-administered with statins (atorvastatin, rosuvastatin or simvastatin). Providers should consider utilizing the apixaban anti-Xa assay or comparative heparin anti-Xa assay to determine if patients require dose reduction to decrease adverse events in high-risk patients prescribed apixaban and concomitant p-glycoprotein and CYP3A4 inhibitors amiodarone or diltiazem with and without a CYP3A4 or non-3A4 statin.