Aprepitant or Ondansetron in Treating Nausea and Vomiting Caused By Opioids in Patients With Cancer

DISEASE CHARACTERISTICS: * History of malignancy (including hematological malignancies) * Has pain requiring opioid analgesics * Nausea and vomiting (associated with opioid analgesic use) that is unrelieved by at least one standard antiemetic regimen (including 5HT3 antagonist and dexamethasone combination therapy) * Patients who have failed ondansetron hydrochloride for treatment of opioid-induced nausea and vomiting will be excluded from the study PATIENT CHARACTERISTICS: * ECOG performance status 0-2 * Able to assess severity of nausea and vomiting and document it in the diary * Women must not be pregnant or lactating * Women of childbearing potential and sexually active males are strongly advised to use an accepted and effective method of contraception * Urine pregnancy test will be given to women of childbearing age * No concerns about compliance with medication regimen or medical follow-up (patient must be able to tolerate oral dosing) * No severe or chronic illness or other causes of nausea and vomiting, that in judgment of the treating physician, will place patient at risk * No severe gastrointestinal obstruction or active peptic ulcer disease * Serum ALT and AST \< 2 times upper limit of normal (ULN) * Serum bilirubin \< 2 times ULN * Serum alkaline phosphatase \< 2 times ULN PRIOR CONCURRENT THERAPY: * No surgery within the past 7 days * No chemotherapy within the past 7 days * No total or lower body radiation therapy within the past 7 days * Patient may not…