ICU Patients 18 Years or Older. Clinical Trial
Official title:
Pharmacokinetics of Fondaparinux (Arixtra) to Critically Ill Patients on Vasopressor Therapy
Patients in intensive care units have higher risks for developing blood clots. Arixtra inhibits blood clot formation by binding with the blood clotting factor, Xa. Critical illnesses and, specifically, medications given in the ICU to increase arterial blood pressure (vasopressors) may impair the absorption of drugs like Arixtra that are given subcutaneously. The study will measure the levels of Arixtra in blood comparing those subjects who are and those subjects who are not on blood pressure medication.
In view of the high risk of venous thrombolism (VTE) in critically ill patients, it is
essential for all ICUs to develop a standardized approach to thromboprophylaxis. Several
studies in a critical setting have shown that both low dose unfractionated heparin and low
molecular weight heparin (LMWH) reduce the incidence of VTE and either one of them is
recommended as a valid agent by the newer ACCP consensus guidelines.
However, even with prophylaxis, critically ill patients still develop VTE. Common conditions
amongst ICU patients such as generalized edema, poor peripheral perfusion during shock
states, moderate renal dysfunction, etc., are possible explanations for this observation.
Additionally, the use of vasoactive drugs may also impair peripheral circulation and reduce
effective levels of agents used for the prevention of VTE.
This prospective clinical trial will be conducted to assess whether impaired peripheral
circulation due to vasopressor (blood pressure) infusion decreases the bioavailability
(i.e., plasma concentration) of subcutaneously administered fondaparinux (i.e., does
vasopressor infusion lower blood plasma concentrations of fondaparinux), thereby reducing
the prophylactic benefits of fondaparinux administration.
Fondaparinux (Arixtra®) was chosen as the anti-thrombotic agent to be used in this study
because of its unique pharmacological properties and its safety and efficacy amongst
different medical populations. Fondaparinux sodium administered by subcutaneous injection is
rapidly and completely absorbed (absolute bioavailability is 100%). Following a single
subcutaneous dose of fondaparinux sodium 2.5 mg in young male subjects, Cmax of 0.34 mg free
acid/L is reached in approximately 2 hours. In patients undergoing treatment with
fondaparinux sodium injection 2.5 mg, once daily, the peak steady-state plasma concentration
is, on average, 0.39-0.50 mg free acid/L and is reached approximately 3 hours post-dose.
Because fondaparinux does not react with platelet factor IV, thrombocytopenia is not an
unwanted side effect.
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Observational Model: Defined Population, Time Perspective: Longitudinal