| Summary: | Background As a strong opioid, methadone has unique advantages in relieving refractory carcinous pain, but also has some limitations, such as higher risk of accumulation due to long elimination half-life, difficulties in dosage calculation and dose conversion due to significant differences between individuals, and limited clinical evidence on the use of this medicine in large doses. Objective To investigate the efficacy and safety of methadone conversion in patients with refractory carcinous pain. Methods A total of 100 inpatients with refractory carcinous pain were recruited from Cancer Hospital of the University of Chinese Academy of Sciences/Zhejiang Cancer Hospital from July 2017 to December 2021. The conversion of morphine to methadone was carried out by rapid conversion or 3-day conversion method. The doses of methadone used at one week and two weeks after the conversion, the daily mean pain intensity assessed by the Numeric Rating Scale (NRS), number of breakthrough pain and adverse reactions before and after methadone conversion were recorded. The efficacy and safety of methadone conversion were analyzed. Results There was a dynamic conversion ratio between morphine and methadone. The conversion ratio between morphine and methadone increased with the growth of the daily dose of morphine. Ninety-six cases finally completed methadone conversion. The mean NRS score and the number of breakthrough pain were significantly reduced at one week or two weeks after the conversion (P<0.05). The rate of the most severe pain relief and the rate of average pain relief were 68.8% and 75.0%, respectively, at one week after methadone conversion, and were 69.8%, and 77.1% respectively, at two weeks after methadone conversion. The main adverse reactions to methadone included dry mouth, nausea, vomiting, constipation, dizziness and cold sweat. Compared with before conversion, the incidence of nausea (χ2 pair =7.005, 8.233) and vomiting (χ2 pair =5.581, 10.907) were decreased at one week and two weeks after conversion (P<0.05) . Conclusion This study confirmed through clinical practice that methadone can reduce the mean NRS score and the number of breakthrough pain in patients with refractory cancer pain, relieve the pain intensity of patients to a certain extent, and reduce the incidence of some adverse reactions.
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