Methadone as an Alternative Treatment for Children Underdoing HSCT

Mucositis is a normal side effect of stem cell transplant which happens as a result of chemotherapy being given prior to a new donor cell infusion (bone marrow transplant). The chemotherapy will kill cancer cells, but good cells, such as those in the mouth, are killed too. The mouth cells going away causes the areas in the mouth to be blistered, irritated, sore, and extremely painful. Pain medication (usually morphine or hydromorphone if allergic to morphine) are given when oral blisters are seen or felt by patient in patient's mouth. However, one pain medication given through a vein in the patient may or may not be effective and providers are often challenged with providing good pain control while waiting for the new donor cells to grow, which will then heal the mouth. This is a period of waiting that is 6-8 weeks. The investigators know that methadone, a second pain medication, may decrease pain in a different way than morphine. This is because methadone works in a different way in the brain than morphine. By giving these pain medicines together, the hope of the study is to show decreased pain while waiting for new cells to grow. The goal of this clinical trial is to hope to learn whether adding methadone (second pain medication) to the current pain medication which is morphine alone (all patients will receive this pain medication) will help reduce the pain experience of participant. Current treatment of morphine alone is sometimes not entirely effective and so any improvement of pain while waiting for new cells to grow is one of the goals of this study. If methadone is effective in decreasing pain, then patients may benefit in the future from using these two medications up front when getting a transplant. Participant in this study between 6-18 years of age and is needing a stem cell transplant for a disease that can potentially be cured by transplantation. Participant in this study is receiving chemotherapy and/or radiation conditioning that can cause mucosit