Key result
In patients taking apixaban 5-mg twice daily, 63.6% and 81.8% of those with an initial trough or peak level in the upper quintile, respectively, maintained a high level when retested at 2 months.
Why the study?
Off-label apixaban dose reduction to prevent bleeding may increase stroke risk; the study evaluated whether a single high drug level predicts high levels at 2 months to identify candidates for dose reduction.
Does a single measurement of high apixaban levels predict persistently high levels at 2 months in patients receiving apixaban for AF or VTE?
Cohort (n=100)
No
Does a single measurement of high apixaban levels predict persistently high levels at 2 months in patients receiving apixaban for AF or VTE?
A single measurement of high apixaban levels reliably predicts persistently high levels at 2 months, which may help identify patients suitable for off-label dose reduction to mitigate bleeding risk.
Single high apixaban levels may persist at 2 months; hypothesis-generating for level-guided dosing but should not yet change practice.
Background Patients with atrial fibrillation (AF) are frequently treated with apixaban 2.5-mg twice daily (BID) off-label, presumably to reduce the bleeding risk. However, this approach has the potential to increase the risk of ischemic stroke. If a single measurement could reliably identify patients with high drug levels, the increased stroke risk may be mitigated by confining off-label dose reduction to such patients. Objectives This study aimed to determine whether a single high apixaban level is predictive of a similarly high level when the test is repeated in 2 months. Methods In this prospective cohort study of clinic patients receiving apixaban 5-mg BID for AF or venous thromboembolism, peak and trough apixaban levels were measured using the STA-Liquid anti-Xa assay at baseline and 2 months. We calculated the proportions of patients with levels that remained in the upper quintile. Results Of 100 enrolled patients, 82 came for a second visit, 55 of whom were treated with apixaban 5-mg BID. Seven (63.6%, 95% confidence interval [CI]: 35.4–84.8%) and nine (81.8%, 95% CI: 52.3–94.9%) of 11 patients with a baseline trough and peak level in the upper quintile, respectively, had a subsequent level that remained within this range. Only one (9.1%, 95% CI: 1.6–37.7%) patient had a subsequent level that fell just lower than the median. Conclusion The trough and peak levels of apixaban in patients who have a high level on a single occasion, usually remain high when the assay is repeated in 2 months. Accordingly, the finding of a high apixaban level in patients deemed to be at high risk of bleeding, allows physicians contemplating off-label use of the 2.5-mg BID dose to limit its use to selected patients who are less likely to be exposed to an increased risk of thrombosis.
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Vries et al. (2022) conducted a cohort in Atrial fibrillation or venous thromboembolism (n=100). Apixaban was evaluated on Proportion of patients with a baseline trough level in the upper quintile whose subsequent level remained in the upper quintile at 2 months (95% CI 35.4-84.8). In patients taking apixaban 5-mg twice daily, 63.6% and 81.8% of those with an initial trough or peak level in the upper quintile, respectively, maintained a high level when retested at 2 months.
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