Life threatening retroperitoneal haemorrhage due to therapeutic fondaparinux.

We report the case of a patient with pulmonary embolism, treated with fondaparinux as bridging therapy until therapeutic levels were achieved on warfarin, who developed a non-traumatic massive retroperitoneal haematoma requiring substantial resuscitation with blood products and arterial embolisation. To our knowledge, this condition has not been reported with therapeutic doses of fondaparinux. Our patient, however, may have been more predisposed to bleeding due to the unpredictable pharmacokinetics of fondaparinux secondary to his morbid obesity, reduced clearance of the drug due to renal insufficiency and concomitant treatment with low dose aspirin and warfarin. Another consideration was the lack of a specific reversing agent for fondaparinux in the setting of a life threatening haemorrhage.