Anti-Xa Levels in Morbidly Obese Patients Using Apixaban or Rivaroxaban, Before and After Bariatric Surgery.

Background: Despite limited evidence about the efficacy and safety of anticoagulation in patients post bariatric surgery, both vitamin K antagonists (VKA) and direct-acting oral anticoagulants (DOACs) are commonly prescribed.

Aim: To evaluate plasma anti-Xa levels of DOACs in morbidly obese (MO) patients before and after a Roux-en-Y gastric bypass (RYGB) procedure.

Patients And Methods: Retrospective, cross-sectional, and longitudinal study of anti-Xa activity of apixaban or rivaroxaban in MO patients (N = 41).

Results: Preoperative analysis of plasma anti-Xa levels were within the normal range in patients using apixaban (n = 29; body mass index [BMI] 44.5 ± 5.1 kg/m) as well as those using rivaroxaban (n = 12; BMI 42.6 ± 5.9 kg/m). Postoperative anti-Xa levels of apixaban were all within the therapeutic range, whereas anti-Xa levels of rivaroxaban were subtherapeutic in nine out of 14 (64%) patients. Perioperative longitudinal follow-up in patients using apixaban (n = 18) showed no significant change in anti-Xa levels after RYGB.

Conclusion: Plasma anti-Xa levels of apixaban in MO patients remained within the therapeutic range up to a body weight of 144 kg. In patients using rivaroxaban, no statistically significant relation between anti-Xa levels and bodyweight was found. After RYGB, plasma anti-Xa levels of apixaban were unaffected, whereas plasma anti-Xa levels of rivaroxaban tended to become subtherapeutic.