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.
Goldstein et al. (2026) studied this question.