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.

To investigate the efficacy and safety of methadone conversion in patients with refractory carcinous pain.

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.

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) .

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.

美沙酮属于强阿片类药物，在难治性癌痛的治疗中有其独特的优势，但同时美沙酮具有t_1/2长、易引起药物蓄积等特性，个体差异大，因此其剂量的把握及转换较为复杂，且在需要较大剂量阿片类药物的患者中应用经验更为有限。

探讨盐酸美沙酮片治疗难治性癌痛患者的疗效和安全性。

选取2017年7月至2021年12月在中国科学院大学附属肿瘤医院（浙江省肿瘤医院）住院的100例难治性癌痛患者为研究对象，采用美沙酮快速转换或3天转换法进行美沙酮转换，统计转换后1周及2周美沙酮剂量，同时记录美沙酮转换前后日平均疼痛强度〔以疼痛数字评分法（NRS）评分评价〕、爆发痛次数及不良反应等，对难治性癌痛患者美沙酮转换的疗效和安全性进行分析。

吗啡与美沙酮存在动态转换比关系，吗啡日剂量越大，与美沙酮之间的转换比也越大。100例难治性癌痛患者中有96例患者最终完成美沙酮转换，与转换前相比，96例患者美沙酮转换后1周、2周平均NRS评分、爆发痛次数均降低（P<0.05）。96例患者美沙酮转换后1周，最严重疼痛强度和平均疼痛强度的有效缓解率分别为68.8%和75.0%；转换后2周，最严重疼痛强度和平均疼痛强度的有效缓解率分别为69.8%和77.1%。美沙酮的不良反应主要有口干、恶心、呕吐、便秘、头晕和冷汗等；与转换前相比，转换后1周、2周恶心（χ²_配对=7.005、8.233）、呕吐（χ²_配对=5.581、10.907）发生率均降低（P<0.05）。

本研究通过临床实践证实美沙酮可降低难治性癌痛患者的平均NRS评分、爆发痛次数，对患者的疼痛强度有一定缓解作用，并能降低部分不良反应发生率。