- Patients receiving anticoagulants who have prothrombin and partial thromboplastin times outside of the normal range for the laboratory assays; patients who are on anticoagulation or antiplatelet medications (e.g. dipyridamole, ticlopidine, warfarin derivatives) who are not receiving a stable dose for 3 months before baseline; patients who are receiving warfarin-derivative anticoagulants who do not have an International Normalized Ratio (INR) in the therapeutic range for the clinical indication for which the anticoagulant has been prescribed.