Megestrol Acetate With or Without Mirtazapine in Treating Cancer Patients With Weight Loss or Loss of Appetite

Inclusion Criteria: * Patient must have a histologically or cytologically confirmed solid malignancy * Patient must be \>=18 years old. * Patient must have shown unintentional weight loss of \>= 5% in 6 weeks dating back from time of consent or \>= 10% in 6 months dating back from time of consent * Patient must have a poor appetite (defined as a score of =\< 14 on the Simplified Nutritional Appetite Questionnaire (SNAQ) * Prior diagnostic or therapeutic surgery is allowed as long as the wound has fully healed, the patient has fully recovered from the procedure, and at least 4 weeks have elapsed from the procedure; for needle or core biopsy, or minimally invasive procedures such as chest tube placement, this 4-week recovery period does not apply, but the patient must have recovered fully from the procedure * Concomitant administration of chemotherapy is permitted but not required * Prior radiation therapy is allowed for local symptom palliation prior to the start of treatment as long as at least 2 weeks have elapsed from the procedure and the patient has fully recovered from treatment-related toxicities * Patient must have an Eastern Cooperative Oncology Group (ECOG) performance status =\< 2 * Patient must have normal organ and marrow function as defined below: * Leukocytes \>= 3,000/mcL * Absolute neutrophil count \>= 1,500/mcL * Platelets \>= 100,000/mcL * Total bilirubin within normal institutional limits * Aspartate aminotransferase (AST) (serum glutamic oxaloacetic trans…