Thrombotic thrombocytopenic purpura may occur after a short exposure (<2 wk). Patients w/ hematopoietic disorders eg, neutropenia or thrombocytopenia, hemorrhagic diathesis or other hemorrhagic disorders associated by a prolonged bleeding time or conditions w/ an increased risk of bleeding eg, GI ulcers, acute cerebral hemorrhage or severe liver dysfunction. Perform full blood counts prior to treatment & every 2 wk during 1st 3 mth of therapy & w/in 2 wk after treatment. Discontinue therapy 10-14 days before elective surgery.