Bleeding disorder or haemorrhage, cerebrovascular event, uncontrolled HTN, head injury, severe liver disease, peptic ulcer, oesophageal varices, blood vessel abnormalities, certain tumours, pericarditis, endocarditis, concomitant use w/ anticoagulants, pancreatitis, recent major surgery, including brain or spinal surgery, CPR for >2 min duration in the last 2 wk.