Patients who receive a chemotherapy called melphalan are at high risk of having nausea and vomiting. A medication called olanzapine has been shown to decrease nausea and vomiting after chemotherapy. A previous research study found the 10 mg dose of olanzapine (combined with 3 standard medications used routinely to prevent nausea/vomiting) to be effective for patients who received melphalan chemotherapy, but several other studies have shown many patients have a side effect of sleepiness (e.g., sedation) with that dose of the medication. Our study will compare two lower doses of olanzapine (5 mg and 2.5 mg) in combination with the 3 standard medications used to prevent nausea/vomiting in the patients who receive melphalan chemotherapy to determine which dose is effective in preventing nausea and vomiting with the lowest amount of sleepiness side effect.

This study is a randomized, double-blinded trial comparing olanzapine 2.5 mg vs 5 mg in combination with standard triplet antiemetic prophylaxis in patients with multiple myeloma who are receiving high-dose melphalan conditioning chemotherapy before autologous stem cell transplantation to determine chemotherapy-induced nausea and vomiting (CINV) and sedation outcomes.

Inclusion Criteria:

• Receipt of high-dose melphalan 140-200 mg/m2
• Autologous stem cell transplantation recipient

Exclusion Criteria:

• Allergy to olanzapine
• Documented nausea or vomiting within 24 hours prior to enrollment
• Treatment with other antipsychotic agents such as risperidone, quetiapine, clozapine, phenothiazine, or butyrophenone within 30 days prior to enrollment or planned during protocol therapy
• Chronic alcoholism
• Pregnant
• Decline or unable to provide informed consent