 - - Use of the following medications: unfractionated heparin to treat an active thrombotic event within 8 hours before the infusion; low-molecular-weight heparin at a higher dose than recommended for prophylactic use within 12 hours before the infusion, warfarin used within 7 days of study entry, aspirin use at a dose of more than 650 mgday within 3 days before the study, thrombolytic therapy within 3 days before the study, glycoprotein IIbIIIa antagonists within 7 days before the study entry, administration of activated protein C Xigris in the 24 hours before study entry. 