Administration and toxicity– We administer UDCA (total daily dose 12 mg/kg or 600 mg orally, divided in two doses) beginning the day before the preparative regimen begins (ie, day –1) and continue treatment for three months. If mucositis or nausea interrupts administration of UDCA, we resume treatment when the patient is again able to take oral medications. UDCA is well-tolerated; the major adverse effects are rash and diarrhea in