• the incidence of clinically significant bleeding, defined as hemodynamically significant bleeding or requiring blood transfusions while being treated with fondaparinux [ Time Frame: daily monitoring ] [ Designated as safety issue: Yes ]
  

• the incidence of venous or thrombotic events after starting treatment with fondaparinux [ Time Frame: monitored daily while taking fondaparinux, weekly for 4 weeks after stopping fondaparinux ] [ Designated as safety issue: Yes ]
  

Drug: fondaparinux
dosage form: subcutaneous injection dosage: 7.5 to 10.0 mg frequency and duration: daily until blood test results rule out confirmed HIT; for patients with confirmed HIT, continue daily until INR (blood clotting) measurement rises to at least 2
Drug: warfarin
dosage form: oral dosage: 2.5 to 5.0 mg frequency and duration: (for confirmed HIT only) once daily, to begin when blood platelet count reaches at least 100,000, and continue for approximately 4 weeks

Currently, standard treatment of HIT involves the transition from a direct thrombin inhibitor (a type of anticoagulant or "blood thinner") to warfarin, a different type of anticoagulant. Direct thrombin inhibitors (DTIs) require IV administration and frequent blood draws for dose adjustments, which can lead to prolonged hospitalization. DTIs also affect blood test measurements, making it difficult to determine proper dosages of warfarin.

Fondaparinux is a drug that is approved by the FDA for the treatment of blood clots in deep veins and in the lungs. Fondaparinux is not FDA approved for the treatment of HIT. However, an increasing number of doctors are using fondaparinux instead of DTIs to treat HIT. Although fondaparinux appears to be more convenient and predictable than DTI medications, more research is needed to support its use as a treatment for HIT.