Key result
Standard apixaban dosing in patients weighing ≥120 kg or with BMI ≥40 kg/m2 showed weight negatively correlated with peak anti-Xa levels (r=-0.42, p=0.002), though only 9% had subtherapeutic peaks.
Why the study?
Recent guidelines suggest standard apixaban doses are appropriate for VTE in patients with BMI >40 kg/m2 or >120 kg, but AF is excluded from this recommendation.
Does apixaban achieve adequate anti-Xa levels in severely obese patients (BMI ≥40 kg/m2 or weight ≥120 kg) with AF or VTE?
Cohort (n=55)
No
Does apixaban achieve adequate anti-Xa levels in severely obese patients (BMI ≥40 kg/m2 or weight ≥120 kg) with AF or VTE?
Standard dosing of apixaban in severely obese patients achieves adequate anti-Xa levels, supporting its use for both VTE and AF in this population.
Supports standard apixaban dosing for adequate anti-Xa levels in most severe obesity; leaves open randomized outcome trials in AF and VTE.
BACKGROUND: Recent guidelines suggest that, for venous thromboembolism (VTE), standard doses of apixaban are appropriate in patients with body mass index (BMI) >40 kg/m2 or >120 kg. Atrial fibrillation (AF) is excluded from this recommendation. OBJECTIVE: The goals of our study were to measure and describe anti-Xa levels of patients with a BMI ≥40 kg/m2 and/or a weight ≥120 kg with a clinical indication of AF or VTE who were treated with apixaban, and to determine whether BMI or weight are associated with anti-Xa levels in this population. METHODS: We conducted an observational cohort study at a single health care system in Oregon, USA. Patients meeting enrollment criteria were recruited and had peak and trough apixaban anti-Xa levels drawn. RESULTS: Of 55 patients enrolled, 5 (9%) had peak anti-Xa levels below the reference range and 3 (6%) had trough anti-Xa levels below the reference range. BMI did not significantly correlate with peak or trough anti-Xa levels (r = -0.10, p = 0.45 and r = -0.14, p = 0.31). Weight had a moderate, negative correlation with peak anti-Xa levels (r = -0.42, p = 0.002) and a weak, negative correlation with trough anti-Xa levels (r = -0.32, p = 0.02). CONCLUSIONS AND RELEVANCE: This study provides evidence that anti-Xa levels among obese patients are not substantially different from patients with nomral BMI and weight. This supports recent ISTH guidance for standard dosing of apixaban for VTE patients with BMI >40 kg/m2 or weight >120 kg and provides additional evidence that the standard dosing may also be appropriate in patients with AF.
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Harkness et al. (2022) conducted a cohort in Atrial fibrillation or venous thromboembolism (n=55). Apixaban was evaluated on Peak and trough apixaban anti-Xa levels and their association with BMI or weight. Standard apixaban dosing in patients weighing ≥120 kg or with BMI ≥40 kg/m2 showed weight negatively correlated with peak anti-Xa levels (r=-0.42, p=0.002), though only 9% had subtherapeutic peaks.
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