{"Thioguanine can be affected by a patient's TPMT and NUDT15 phenotype. This patient is predicted to be a NUDT15 poor metabolizer and is at high risk for life threatening myelosuppression with normal doses of thioguanine and should receive greatly reduced doses. Reduce doses to 25% of normal dose and adjust doses of thioguanine based on degree of myelosuppression and disease-specific guidelines. Allow 4-6 weeks to reach steady-state after each dose adjustment. In setting of myelosuppression, emphasis should be on reducing thioguanine over other agents. For non-malignant conditions, consider alternative non-thiopurine immunosuppressant therapy. Because a TPMT genotype does not appear to have been ordered for this patient, it is not known if TPMT results would further influence the recommended dose or drug. If thiopurines are required and TPMT genotype status is unknown, consider evaluating TPMT erythrocyte activity to assess TPMT phenotype. Erythrocyte TPMT activity test results can be falsely low at diagnosis of leukemia and is unreliable in the case of recent red blood cell transfusions. Please consult a clinical pharmacist for more information."}