Inclusion Criteria: - Inclusion: Baseline aPTT values for all subjects must be within normal range. In addition, all subjects must also test negative for occult blood in the stool, have no history of bleeding disorders or no use of aspirin or NSAIDs within 14 days of study Day 1. Exclusion Criteria: - Exclusion: The study will also exclude subjects who have any evidence or history of thrombocytopenia, heparin-induced thrombocytopenia or other contraindications to heparin (e.g., recent surgeries).