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Am J Health Syst Pharm. 2011 Sep 15;68(18):1716-22. doi: 10.2146/ajhp110010.

Effect of fondaparinux prophylaxis on anti-factor Xa concentrations in patients with morbid obesity.

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  • 1Inpatient Pharmacy Department, University of New Mexico Hospital, Albuquerque 87106, USA.

Abstract

PURPOSE:

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.

SUMMARY:

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.

CONCLUSION:

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.

PMID:
21880887
DOI:
10.2146/ajhp110010
[PubMed - indexed for MEDLINE]
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