Update on drug interactions with non-vitamin-K-antagonist oral anticoagulants for stroke prevention in elderly patients

Perioperative Management of Antithrombotic Therapy: An American College of Chest Physicians Clinical Practice Guideline

BACKGROUND

The American College of Chest Physicians Clinical Practice Guideline on the Perioperative Management of Antithrombotic Therapy addresses 43 Patients-Interventions-Comparators-Outcomes (PICO) questions related to the perioperative management of patients who are receiving long-term oral anticoagulant or antiplatelet therapy and require an elective surgery/procedure. This guideline is separated into four broad categories, encompassing the management of patients who are receiving: (1) a vitamin K antagonist (VKA), mainly warfarin; (2) if receiving a VKA, the use of perioperative heparin bridging, typically with a low-molecular-weight heparin; (3) a direct oral anticoagulant (DOAC); and (4) an antiplatelet drug.

METHODS

Strong or conditional practice recommendations are generated based on high, moderate, low, and very low certainty of evidence using the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) methodology for clinical practice guidelines.

RESULTS

A multidisciplinary panel generated 44 guideline recommendations for the perioperative management of VKAs, heparin bridging, DOACs, and antiplatelet drugs, of which two are strong recommendations: (1) against the use of heparin bridging in patients with atrial fibrillation; and (2) continuation of VKA therapy in patients having a pacemaker or internal cardiac defibrillator implantation. There are separate recommendations on the perioperative management of patients who are undergoing minor procedures, comprising dental, dermatologic, ophthalmologic, pacemaker/internal cardiac defibrillator implantation, and GI (endoscopic) procedures.

CONCLUSIONS

Substantial new evidence has emerged since the 2012 iteration of these guidelines, especially to inform best practices for the perioperative management of patients who are receiving a VKA and may require heparin bridging, for the perioperative management of patients who are receiving a DOAC, and for patients who are receiving one or more antiplatelet drugs. Despite this new knowledge, uncertainty remains as to best practices for the majority of perioperative management questions.

Tailored Direct Oral Anticoagulation in Patients with Atrial Fibrillation: The Future of Oral Anticoagulation?

Direct oral anticoagulants (DOAC) are currently the drug of choice for drug prevention of stroke or systemic embolism in patients with atrial fibrillation (AF). However, repeated ischemic stroke or systemic embolism and bleeding while on DOAC is still a challenging clinical phenomenon in the management of future long-term anticoagulation. It is not known whether tailoring the DOAC therapy to achieve optimal therapeutic drug levels could improve the clinical course of DOAC therapy. To be able to tailor the therapy, it is necessary to have a valid laboratory method for DOAC level assessment, to be aware of factors influencing DOAC levels and to have clinical options to tailor the treatment. Furthermore, the data regarding clinical efficacy/safety of tailored DOAC regimes are still lacking. This article reviews the current data on tailored direct oral anticoagulation in patients with AF.

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.