Monitor apixaban concentrations in AF patients with dose-lowering criteria, says study

In patients with atrial fibrillation (AF), off-label underdosed apixaban leads to lower plasma apixaban concentrations than on-label standard and reduced-dose regimens, according to a study.

Moreover, several patients present with apixaban concentrations beyond the expected range. This indicates the potential benefits of monitoring plasma concentrations.

Overall, 374 AF patients (mean age 75.6 years, 54.8 percent female) with dose-reduction criteria for apixaban were included in this observation study. Participants were then grouped into three: on-label standard dose (5 mg twice daily; n=166), on-label reduced dose (2.5 mg twice daily; n=55), and off-label underdose (2.5 mg twice daily; n=153).

Finally, the authors compared apixaban concentrations determined via the anti-Xa assay and thrombin generation assay (TGA) parameters at trough levels.

Patients in the off-label underdose group showed significantly lower apixaban trough concentrations than those in the on-label reduced-dose and standard-dose groups (56.7 vs 83.7 vs 129.9 ng/mL; p<0.001 for all).

Of the patients, <70 percent had apixaban concentration within the expected range. The proportion of patients who exceeded the upper limit of the expected range were significantly lower in the off-label underdose group than in the on-label reduced-dose and standard-dose groups (1.3 percent vs 9.1 percent [p=0.005] vs 12.7 percent [p<0.001]).

Based on the TGA parameters, the on-label standard-dose group exhibited the lowest thrombogenic profiles. Additionally, the most significant predictor of higher apixaban concentrations was lower creatinine clearance.

“Further studies are needed to compare dosages directly, investigate the impact of plasma apixaban concentration monitoring, and validate the current dose-reduction criteria,” the authors said.