• unfractionated heparin to treat an active thrombotic event within 8 hours before the infusion (prophylactic treatment with a dose of unfractionated heparin of up to 15,000 U/day was permitted); • low molecular weight heparin at a higher dose than recommended for prophylactic use (as specified in the package insert) within 12 hours before the infusion; • warfarin (if used within 7 days before study entry and if the prothrombin time exceeded the upper limit of the normal range for the institution); • acetylsalicylic acid at a dose of more than 650 mg/day within 3 days before the study; • thrombolytic therapy within 3 days before the study (thrombolytic agents permitted for the treatment of thromboses within a catheter); • glycoprotein IIb/IIIa antagonists within 7 days before study entry; • antithrombin III at a dose of more than 10,000 U within 12 hours before the study; • protein C within 24 hours before the study.