- The subject requires concomitant treatment, in therapeutic doses, with anti-coagulants such as warfarin or warfarin-related agents, heparin, thrombin or factor Xa inhibitors or antiplatelet agents (i.e. clopidogrel); low dose aspirin (=< 81 mg/day) low-dose warfarin (=< 1 mg/day) and prophylactic low molecular weight heparin are permitted