Utilization and Laboratory Monitoring of Andexanet Alfa Reversal of Factor Xa Inhibitors in Bleeding Patients

Abstract

Abstract Introduction Andexanet alfa, a reversal agent for factor Xa inhibitors rivaroxaban and apixaban, was approved by the Food and Drug Administration in May 2018 for patients with life-threatening bleeding. It acts by competing with endogenous factor Xa to block anticoagulant activity. Intravenous administration rapidly reduces anti-factor Xa activity. Because andexanet became available only recently, there is high potential for inappropriate use. Our objective was to investigate utilization and laboratory monitoring of andexanet in our hospital system in order to improve utilization. Methods This is a retrospective study with review of charts in the electronic medical record from April 2019 to February 2020. Charts were reviewed for the time of andexanet administration, anti-factor Xa testing before and after administration, turnaround time (TAT) for anti-factor Xa testing, and patient’s status after treatment. Results We identified 33 patients who received andexanet in our hospital system. Intracranial hemorrhage was the most common clinical symptom. Of 33 patients, 12 patients (36%) expired, one transferred to hospice, 18 (55%) were discharged alive, and two recent cases are alive awaiting disposition. Only 12 patients (36%) had anti-factor Xa testing performed prior to administration of andexanet, with one additional patient receiving testing only after administration. Factor Xa activity was misordered for anti-factor Xa in one patient. TAT for anti-factor Xa in these patients ranged from 25–112 minutes, with median 35.5 minutes. Of the 12 patients who had anti-factor Xa testing prior to administration, 4 expired and 8 survived. Pre-administration anti-factor Xa activity was significantly lower in patients who expired than in patients who survived (0.3 vs. 1.8 IU/ml, P value = 0.02). Conclusion Currently, anti-factor Xa testing is not ordered for most patients receiving andexanet alfa in our hospital system. Although not necessary for dosing decisions, anti-factor Xa testing may be useful prior to administration to identify patients unlikely to benefit from anticoagulant reversal. Despite a small sample size, there was a statistically significant difference in anti-factor Xa activity by patient outcome, suggesting that andexanet may be unhelpful in patients with low anti-factor Xa activity. Based on these findings, we are building an electronic order set to facilitate proper administration of this medication.