Odansetron and Dexamethasone Alone vs. Odansetron, Dexamethason and Apreptant to Prevent Nausea

Inclusion Criteria: * Diagnosis of cancer, admitted for myelosupppresive stem cell transplantation. Included preparative regimens include: TBI/VP16/CY, TBI/CY, BU/CY (PO \& IV), and BCV * Age 18 or older * Alcohol intake \<100 gm/d for the last year (\< approximately 5 drinks per day) * Renal function: estimated or measured CrCl 50 ml/min * Liver function: T.Bili \<1.5, AST \< 2x ULN, unless due to disease * Able to swallow tablets and capsules Exclusion Criteria: * Age \< 18 * High alcohol intake \[\> 100 gm/d in the last year\] * Allergy or intolerance to: ondansetron or dexamethasone * Renal dysfunction \[measured or estimated CrCl \< 50 ml/min\] * Liver dysfunction \[T.Bili \> 1.5, AST \> 2x ULN, unless due to disease\] * Inability to swallow tablets or capsules * Concurrent condition requiring systemic steroid use * Nonmyeloablative SCT, patients receiving the conditioning regimens not included \[see inclusion criteria\] * History of anticipatory nausea and vomiting