Abstract
Purpose：Methadone is an opioid used in Japan for the treatment of cancer pain. A thorough consideration of complex pharmacokinetics with individual differences and of serious adverse effects is necessary before switching to methadone; therefore, methadone is not yet widely used. We examined the analgesic and adverse effects of methadone through clinical cases and considered the clinical significance of methadone as an opioid analgesic for the treatment of cancer pain. Methods：The clinical course of 44 patients with cancer pain who were switched to methadone from other opioids was analyzed. Results：Out of the 44 cases investigated, 37 cases （84.1％） were successful. In the successful cases, pain intensity before and after methadone administration was reduced from an average of 7.5 to 2.8, respectively, on the numerical rating scale. Strong drowsiness （six cases） and nausea （three cases） were observed as adverse effects. However, no serious effects, such as QT prolongation and respiratory depression, were recognized. Conclusion：For patients with refractory cancer pain who require a high opioid dose, methadone is considered to be one of the alternatives in pain therapeutics.
