Chemical prophylaxis to prevent venous thromboembolism in morbid obesity: literature review and dosing recommendations

Pharmacologic prophylaxis of deep vein thrombosis and venous thromboembolism (VTE) is an important aspect of medical care, particularly in the inpatient setting. Low-molecular weight heparins, heparin, and fondaparinux are commonly used agents to prevent VTE, each of which has well established dosing regimens in patients with normal body mass index. Dosing of these medications in morbidly obese populations (BMI > 40 kg/m2) is not as clearly defined in guidelines. This article reviews published data to support specific dosing regimens and monitoring strategies of these agents in this population. The most validated parenteral agent to prevent VTE in morbidly obese hospitalized patients is enoxaparin, dosed at 40 mg subcutaneously (SC) twice daily. If unfractionated heparin is utilized for prophylaxis in morbidly obese patients, a dose of 7500 units SC three times daily should be considered. Monitoring of anti-factor Xa levels to guide prophylactic dosing is an option, although the utility of this lab test is limited, as target anti-Xa ranges for VTE prophylaxis have not been universally defined and trials have not shown a clear link between anti-factor Xa levels and bleeding or thrombotic events. Additional studies are needed to clearly define the most appropriate dosing strategies in patients with moderate obesity (BMI 35–40 mg/m2) and those with extreme obesity (BMI > 60 mg/m2).