Parenteral anticoagulants for VTE prophylaxis and treatment in patients with obesity

For venous thromboembolism (VTE) (ie deep vein thrombosis [DVT] or pulmonary embolism [PE]) prophylaxis in patients with obesity (body mass index [BMI] 30 kg/m² or more), the optimal dosing of low molecular weight heparin (LMWH) has not been fully determined; however, at the time of writing, there is no clear evidence that higher doses of LMWH are required. For patients with a BMI of 30 to 39 kg/m², standard doses for VTE prophylaxis can be used. For patients with a BMI more than 40 kg/m², an increase in the standard prophylactic dose (eg by 30%) or weight-based dosing may be considered—seek specialist adviceNutescu, 2009Rondina, 2010.

For VTE treatment in patients with obesity, limited data suggests dosing LMWH according to actual body weight for patients up to 150 kg or with a BMI of up to 40 kg/m². Consider a dose-adjusted approach above this weight, using anti-Xa monitoring to achieve target anticoagulation levels. For patients with a high BMI or increased weight, the twice-daily dosage regimen (eg enoxaparin 1 mg/kg twice daily) may be preferred to the once-daily dosage regimen (eg enoxaparin 1.5 mg/kg once daily) because of the lack of data for the once-daily dosage regimen in this patient group and the practicalities of the available formulations.

In the acute phase after bariatric surgery, parenteral anticoagulation is recommended as initial prophylaxis or treatment of VTE; do not use direct-acting oral anticoagulants (DOACs) because absorption of these drugs is decreased in this setting. Consider switching to an oral anticoagulant after at least 4 weeks of parenteral anticoagulation; if using a DOAC, obtain a trough plasma concentration to check absorptionMartin, 2021.