fondaparinux and Obesity--Morbid

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/m(2)) 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/m(2)) and those with extreme obesity (BMI > 60 mg/m(2)).

Topics: Factor Xa; Female; Fondaparinux; Hemorrhage; Heparin; Humans; Male; Obesity, Morbid; Polysaccharides; Venous Thromboembolism; Venous Thrombosis

Anti-factor Xa values in morbidly obese patients receiving standard doses of fondaparinux sodium for the prevention of venous thromboembolism (VTE) were analyzed in a retrospective chart evaluation.. The administration of low-molecular-weight heparins to obese patients (body mass index [BMI] of ≥30 kg/m(2)) at the dose recommended for VTE prophylaxis has been reported to result in increased thromboembolic events and decreased anti-factor Xa levels, and some evidence indicates that weight-based dosing adjustments may be appropriate. To study this phenomenon among morbidly obese patients (BMI of ≥40 kg/m(2)), a review of the charts of 45 adult patients for whom steady-state anti-factor Xa laboratory values were obtained after at least four fondaparinux injections was conducted; in all instances, fondaparinux sodium was given at the standard dose (2.5 mg once daily). Of the total of 47 anti-factor Xa values analyzed, 22 (47%) were below the study institution's target peak range (0.3-0.5 mg/L), 20 values (43%) were within the range, and 5 (11%) were above the range. No documented thromboembolic events occurred during hospitalization in the cases evaluated. A stepwise linear regression analysis of selected demographic and clinical variables indicated that better renal function, male sex, increased BMI, and fewer fondaparinux doses were associated with a greater likelihood of diminished anti-factor Xa activity in the cases evaluated.. Anti-factor Xa concentrations in morbidly obese patients receiving fondaparinux sodium 2.5 mg subcutaneously daily for VTE prophylaxis were within or above the target range in 53% of the instances evaluated.

Topics: Adult; Aged; Anticoagulants; Cross-Sectional Studies; Factor Xa Inhibitors; Female; Fondaparinux; Humans; Linear Models; Male; Middle Aged; Obesity, Morbid; Polysaccharides; Retrospective Studies; Risk Factors; Venous Thromboembolism; Young Adult