Cyproheptadine in Preventing Weight Loss in Children Receiving Chemotherapy for Cancer

INCLUSION CRITERIA: * ≥ 2 years and ≤ 21 years of age at the time of study entry * Scheduled to receive chemotherapy for: * Newly diagnosed: * Non-rhabdo soft tissue sarcomas, scheduled to receive chemotherapy, as well as intermediate or high-risk rhabdomyosarcoma, any stage osteosarcoma and any stage Ewing's sarcoma * Intermediate or high-risk neuroblastoma * Wilms' tumor (Stage III/IV) * Hepatoblastoma (Stage III/IV) * Germ cell tumors (Stage III/IV) * Brain tumors, including medulloblastoma, PNET and ependymomas * AML * Relapsed/recurrent disease (any patient) * Able to register and randomize within 28 days of starting chemotherapy (registration /randomization and start of study agent may occur at anytime up to and including Day 28 after the initiation of chemotherapy) EXCLUSION CRITERIA: * ≥ 29 days after starting chemotherapy * Documented history of unintended weight loss ≥ 5% presumed secondary to cancer within 3 months of study entry * Currently taking cyproheptadine HCl (or have taken cyproheptadine HCl within 3 weeks of study registration) * History of anorexia nervosa or bulimia * Taking other appetite-stimulating medications, i.e. dronabinol (Marinol) during the past three weeks. * Initiation of other appetite enhancing agents, including steroids prescribed for the intent of weight gain, i.e. Megace. Note: Other forms of nutrition therapies, e.g. appetite-stimulating medications, TPN or enteral tube feedings are not allowed during this study. * Children receivin…