Efficacy and safety of morphine versus methadone for patient-controlled analgesia: a randomized clinical trial

The aim of the study was to evaluate the efficacy and safety of intravenous patient-controlled analgesia (PCA) morphine versus intravenous PCA with methadone for postoperative pain management. In a randomized controlled clinical trial, 400 patients were randomly allocated to receive either morphine or methadone delivered via intravenous PCA after surgery. Patients were followed for 24 hours after surgery. Pain and patient satisfaction was assessed via numeric rating scale as well as sedation score. Data on the incidence of nausea and vomiting, severe sedation and pruritus were also collected. Pain scores at 1 and 3 hours postoperatively in the morphine group was significantly higher than methadone group (p < 0.05), but the trend of pain score, sedation score and the incidence of nausea and vomiting during the 24 hours follow-up were not significantly different between groups. Patients in the methadone group had higher ratings of satisfaction than the morphine group (p = 0.001). Incidence of pruritus in morphine group were higher than the methadone group (P-value = 0.006). PCA with methadone might be more effective than PCA with morphine in reducing postoperative pain during the first hours after surgery with less frequency of pruritus.