Anticoagulants are frequently used as thromboprophylaxis and in patients with atrial fibrillation (AF) or venous thromboembolism (VTE). While obesity rates are reaching epidemic proportions worldwide, the optimal dosage for obese patients has not been established for most anticoagulants, including low-molecular-weight heparin (LMWH), non-vitamin K antagonist oral anticoagulants (NOAC), and pentasaccharides (fondaparinux). The aim of the present systematic review was to summarize the current knowledge and provide recommendations on dosage of LMWH, NOAC, and fondaparinux in obese patients (body mass index [BMI] ≥ 30 kg/m2 or body weight ≥ 100 kg). Based on a systematic search in PubMed and Embase, a total of 72 studies were identified. For thromboprophylaxis with LMWH in bariatric surgery (n = 20 studies), enoxaparin 40 mg twice daily, dalteparin 5,000 IE twice daily, or tinzaparin 75 IU/kg once daily should be considered for patients with BMI ≥ 40 kg/m2. For thromboprophylaxis with LMWH in nonbariatric surgery and in medical inpatients (n = 8 studies), enoxaparin 0.5 mg/kg once or twice daily or tinzaparin 75 IU/kg once daily may be considered in obese patients. For treatment with LMWH (n = 18 studies), a reduced weight-based dose of enoxaparin 0.8 mg/kg twice daily should be considered in patients with BMI ≥ 40 kg/m2, and no dose capping of dalteparin and tinzaparin should be applied for body weight < 140 kg. As regards NOAC, rivaroxaban, apixaban, or dabigatran may be used as thromboprophylaxis in patients with BMI < 40 kg/m2 (n = 4 studies), whereas rivaroxaban and apixaban may be administered to obese patients with VTE or AF, including BMI > 40 kg/m2, at standard fixed-dose (n = 20 studies). The limited available evidence on fondaparinux (n = 3 studies) indicated that the treatment dose should be increased to 10 mg once daily in patients weighing > 100 kg.
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