Note: Recommendations provided are general guidelines only and primarily based on expert opinion; individualize therapy as best as possible. There are limited data in patients with obesity demonstrating changes in apixaban drug concentrations or anti–factor Xa activity (Kido 2020; Piran 2018; Rocca 2018; Sebaaly 2020). A pharmacokinetic study in patients with obesity (>120 kg) suggests ~30% decrease in Cmax and ~20% decrease in AUC; however, the decrease in exposure is unlikely to require a change in dosing (Upreti 2013). If used in a patient with a BMI >40 kg/m2 or weight >120 kg, the International Society on Thrombosis and Haemostasis suggests measuring peak and trough exposure using an anti–factor Xa assay or mass spectrometry calibrated to apixaban. However, there is a lack of data to support apixaban dose adjustment based on anti–factor Xa activity or drug levels. Alternatively, vitamin K antagonists may be considered over apixaban in this patient population if therapeutic drug monitoring is necessary or in patients on apixaban with blood levels below the expected range (ISTH [Martin 2016]; Wasan 2019).