Under den indledende behandling sås større blødninger hos 1, 3% af de patienter, der fik fondaparinux, sammenlignet med 1, 1% af dem, der fik ufraktioneret heparin.
30 Major bleeding during the initial treatment period was observed in 1.3% of fondaparinux patients, compared to 1.1% with unfractionated heparin.