Bioavailability of fondaparinux to critically ill patients

IntroductionVenous thromboembolism is a common problem in the intensive care unit (ICU). To decrease its incidence, prophylactic pharmacologic interventions are part of the ICU routine. However, common ICU conditions may impair the bioavailability of subcutaneously administered agents. The present study evaluates the bioavailability of prophylactic subcutaneous fondaparinux to critically ill patients.PurposeThe purpose of the study was to evaluate vasopressor effect on the bioavailability of subcutaneously administered fondaparinux.Materials and MethodsA 2-center, prospective, observational study was performed. Forty patients were enrolled and divided into 2 groups depending on their vasopressor requirements. All subjects were critically ill patients admitted to a medical ICU for an anticipated stay of more than 72 hours.InterventionsAll patients received subcutaneous fondaparinux 2.5 mg/d, and serum anti-Xa factor was serially assessed during the first 100 hours of medical ICU stay.ResultsTherapeutic anti-factor Xa levels among patients receiving vasopressors were observed. In hemodynamically normal patients, subtherapeutic concentrations were detected during the first 48 hours of fondaparinux administration.ConclusionsVasopressor therapy does not appear to affect fondaparinux bioavailability or to reduce anti-factor Xa levels. Subtherapeutic concentrations were detected during the first 48 hours of fondaparinux administration in hemodynamically stable patients. The clinical significance of reduced levels during the first 2 days of fondaparinux administration remains unknown.