Abstract
Background: Methadone can only be administered orally in Japan. However, it is unclear how to treat pain when patients become unable to take methadone orally because of the progression of the disease. Aims: To assess retrospectively end-of-life pain control management after patients become unable to take methadone orally. Methods: Twenty-eight patients with cancer pain undergoing treatment with oral methadone died at a palliative care unit between April 2013 and September 2014. All patients died of cancer and were unable to swallow before death. We assessed pain control approaches after the patients became unable to take methadone orally. Results: Twenty-one patients survived 1 day or longer after becoming unable to swallow. Methadone was switched to another opioid because of pain. Of these 21 patients, 10 patients survived for 1 week or longer after being switched to another opioid. At this point, methadone would be mostly eliminated from the blood circulation. Among these 10 patients, seven patients were treated with subcutaneous morphine, and three patients were excluded because their pain could not be evaluated. The conversion ratio from final oral methadone dosage to oral morphine equivalent dose of opioids used on the seventh day was 6.1. Conclusion: Even when patients become unable to ingest methadone, switching to other opioids may not always be necessary because of the long half-life of methadone when pain is absent at the end of life. If necessary, pain could be managed by switching to other opioids with a conversion ratio of 6.1.
