Pediatric Experience with Fondaparinux in Deep Venous Thrombosis.

Over the past two years we have employed daily SC fondaparinux as longterm anticoaguation in five pediatric patients who presented with deep venous thrombosis (DVT; 3 cases) or DVT combined with heparin-induced thrombocytopenia (HIT) confirmed by ELISA for HIT antibody ( 2 cases). The Table summarizes characteristics of the patients. In all cases, anti-factor Xa levels were obtained 3–4 hrs after the third dose and were in the range of 0.5 to 1.2 IU/ml, calibrated to fondaparinux. Indications for fondaparinux were outpatient treatment of HIT or suspected HIT (2 cases), a desire for true once-daily outpatient dosing of a SC agent (3 cases), or a desire to minimize volume of agent given SC (2 cases). Dosing for Pt 1 was based upon a calculated enhanced renal excretion of fondaparinux in very young children, assuming drug metabolism to vary as (body mass}^0.75 rather than as body mass. Pt 5 had previously required 10,000 IU of a low MW heparin SC bid, in view of her heterozygous ATIII deficiency, and suffered recurrent hematomas at the injection sites. These almost entirely resolved with use of fondaparinux and a consequent 60% reduction in the daily injected volume of anticoagulant. There have been no episodes of recurrent thrombosis and no bleeding complications after a mean pt follow-up of 8.5 months. Thus, fondaparinux can be employed safely and effectively in both young children and adolescents, with and without HIT.