·       Diagnosis is based on both clinical and serologic grounds. HIT antibody seroconversion without thrombocytopenia or other clinical sequelae is not considered HIT. HIT is seroconversion with unexplained platelet count fall, usually > 50%, even if nadir remains > 150 x 10⁹/liter, or skin lesions at heparin injection sites or acute systemic reactions (fever, chills, cardiorespiratory distress: hypertension, tachycardia, dyspnea, chest pain, cardiorespiratory arrest) within 30 minutes of IV heparin bolus administration.  Although heparin-induced antibody formation occurs in 10-20% of patients treated with heparin, the vast majority of these patients never develop HIT.  Rapid onset HIT, platelet count falling with 24 hours of heparin, is strongly associated with recent heparin exposure within the past 100 days.

Fondaparinux (Arixtra®) was approved by MEC not to be added to formulary in 9/2002 due to bleeding concerns and lack of reversibility. It is recommended for formulary inclusion at this time and will be restricted to hematologists for patients who have or have had heparin induced thrombocytopenia or who are allergic to LMWH. Pharmacy will automatically adjust the dose of fondaparinux, when ordered for DVT/PE treatment, based on the patient’s renal function and lean body weight.

o       Pharmacy will determine the patient's creatinine clearance and lean body weight before dispensing fondaparinux.

o       Patients will not receive fondaparinux unless a recent serum creatinine has been determined and the calculated creatinine clearance is > 30 ml/min.

o       Fondaparinux prophylaxis should not be given to patients weighing < 50 kg following orthopedic surgery.

o       Fondaparinux is contraindicated in patients with bacterial endocarditis

o       Patients receiving fondaparinux will have a serum creatinine and BUN determined every other day during therapy.

o       Fondaparinux Anti Xa levels will be drawn on all patients.

Fondaparinux Dosing, Dosing Tools: Based on Lean Body Weight, & Based on Levels