OBJECTIVES:~Primary~Compare the efficacy of standard antiemetic therapy comprising ondansetron and dexamethasone combined with either aprepitant or placebo in controlling nausea and vomiting, as determined by the number of retch/emesis-free days, in patients undergoing hematopoietic stem cell transplantation.~Secondary~Determine the safety of aprepitant in these patients.~Compare nausea, appetite, taste changes, nutritional intake, and mucositis in patients treated with these regimens.~Determine the pharmacokinetics of cyclophosphamide, carboxyethylphosphoramide mustard, hydroxycyclophylamide, and aprepitant in these patients.~OUTLINE: This is a randomized, placebo-controlled, single-blind, pilot study. Patients are randomized to 1 of 2 treatment arms.~Arm I: Beginning on the first day of conditioning chemotherapy, patients receive oral aprepitant once daily and standard antiemetic therapy comprising oral or IV ondansetron and oral dexamethasone.~Arm II: Patients receive oral placebo once daily and standard antiemetic therapy as in arm I.~In both arms, treatment continues until day 4 after stem cell transplant in the absence of unacceptable toxicity.~After completion of study therapy, patients are followed until day 18.~PROJECTED ACCRUAL: A total of 40 patients (20 per treatment arm) will be accrued for this study.
RATIONALE: Antiemetic drugs, such as aprepitant, ondansetron, and dexamethasone, may help lessen or prevent nausea and vomiting in patients undergoing a stem cell transplant.~PURPOSE: This randomized clinical trial is studying aprepitant, ondansetron, and dexamethasone to see how well they work compared to placebo, ondansetron, and dexamethasone in preventing nausea and vomiting in patients who are undergoing a stem cell transplant.