In addition, the patient is screened at diagnosis and found to have the TPMT polymorphism. Administration of the standard dose (75 mg/m2/day) of 6-mercaptopurine will increase the patient’s bone marrow toxicity (anemia, thrombocytopenia, and neutropenia) due to decreased 6-mercaptopurine metabolism The APN is given a report of the TPMT polymorphism and orders a reduced dose (60 mg/m2/day) of 6-mercaptopurine as recommended. The patient will be monitored closely or bone marrow toxicity by both the APN and the staff nurse, with further reduction in dose if needed.