Utilization of Apixaban Pharmacokinetics for Dose Optimization in High-Risk Elderly Patients

A total of 127 patients were included (median age 79 years, maximum age 97 years; 51% female). At baseline, 16% had subtherapeutic apixaban plasma concentrations and 20% had supratherapeutic concentrations. Female sex was associated with subtherapeutic concentrations while a standard dose (10 mg/day) of apixaban was associated with supratherapeutic plasma concentrations. Dose adjustment was more common in patients with standard dose therapy and in patients with an out-of-range baseline apixaban measurement with adjusted odds ratio of 6.1 and 95% confidence interval of 2.2-16.9 and 4.9 (95% confidence interval 1.9-12.7), respectively. In patients who had undergone repeated apixaban maximum plasma concentration measurements, we found 24 bleeding events and six thrombotic or embolic events within a 1-year follow-up from the second maximum plasma concentration measurement. Bleeding events were more common in patients whose maximum plasma concentration was out of the therapeutic range (28% vs 15%), CONCLUSIONS: Dose adjustment based on apixaban plasma concentration monitoring increased the proportion of patients who have apixaban concentrations within the therapeutic range. In high-risk elderly patients, an apixaban concentration measurement coupled with active intervention (e.g., dose adjustment) is likely to be clinically beneficial in avoiding bleeding and thromboembolic events.