Methadone to Treat Painful Chemotherapy Induced Peripheral Neuropathy

Chemotherapy induced peripheral neuropathy (CIPN) or nerve pain, is a painful and debilitating complication which can chronically affect up to 70% of patients who receive chemotherapy. It causes "glove-and-stocking" distribution of nerve-pain, weakness, and other debilitating symptoms. This can affect patient's quality of life, function, ability to tolerate chemotherapy, and return to work. Duloxetine is the only recommended medication to reduce the painful symptoms and consequences of CIPN by national and international groups such as the American Society of Clinical Oncology. However, studies indicate it only has modest effect; for example, the largest study shows it only reduces pain by 0.73/10 points compared to placebo. Another promising medication in theory and practice is methadone. It is a commonly used and well-studied opioid with unique attributes which allows it to treat non-cancer and cancer associated nerve-pain with better efficacy when compared to other opioids. Furthermore, patients appear to develop less tolerance to methadone over time when compared to other opioids; this is helpful as many develop long-term CIPN and may greatly benefit from long-term pain medication. Therefore, if a patient requires chronic opioids to reduce the painful symptoms of CIPN, one that develops less tolerance is invaluable. Despite the promising role for methadone to treat CIPN, it has not been studied to treat this condition. Therefore, methadone may never be considered by prescribers to reduce the painful symptoms of CIPN. This study is a randomized controlled trial to assess the efficacy of methadone compared to duloxetine to treat painful CIPN. Participants will be randomized to receive either methadone or duloxetine regularly for 5 weeks. Methadone and duloxetine will be placed in indistinguishable capsules, so the participant and assessor are not aware of their treatment. They will be followed virtually or in-person weekly for 5 weeks where they will answer brief questionnaires detailing the effect of their treatment on their pain and their dose will increase weekly as tolerated until their pain is controlled or its the end of the study. This study would be critical in assessing the efficacy of a very promising medication to reduce the painful symptoms of CIPN: a debilitating disorder with otherwise few treatment options.