Pilot Study of Olanzapine and Aprepitant to Prevent Nausea and Vomiting in Children Receiving Chemotherapy

The purpose of this study is to determine the feasibility of a larger trial comparing olanzapine and aprepitant and to obtain preliminary data on the effectiveness of these two medications to treat nausea and vomiting in children receiving chemotherapy. Children receiving 2 cycles of chemotherapy with a high risk of causing nausea and vomiting will receive olanzapine in one cycle and aprepitant in another cycle. Children will be randomized to see which medicine they receive first. The investigators will record the number of extra medications used for nausea, the number of times a child vomits, and the amount of nausea the child feels each day.