Methadone versus morphine for postoperative analgesia in gynecological laparoscopy: protocol for a randomized controlled trial
Idelberto do Val Ribeiro-Junior, Luiz Gustavo Oliveira Brito, Ana Paula da Silva Rios, Helymar Costa Machado, Angelica de Fatima de Assuncao Braga, Vanessa Henriques Carvalho
Abstract
Background: Methadone has unique pharmacological properties among opioids, including N-methyl-D-aspartate receptor antagonism and a long half-life, which may enhance postoperative analgesia. Evidence regarding its efficacy and safety in gynecological laparoscopic surgery remains limited. This study protocol will compare intraoperative methadone and morphine regarding postoperative pain, opioid consumption, cardiac safety, and patient-reported outcomes. The primary objective is to compare the analgesic effects of methadone and morphine during the first 24 hours following gynecologic surgery. Methods: This study protocol, randomized, double-blind, parallel-group clinical trial will be conducted at a tertiary gynecologic care hospital. Adult women undergoing gynecological laparoscopy will be randomly assigned to receive intravenous methadone or morphine at a dose of 0.15 mg/kg of ideal body weight, 60 minutes before the end of surgery. The primary outcome is postoperative pain at rest and during movement within the first 24 hours, measured using the Visual Analog Scale (VAS). Pain will also be assessed at the third postoperative month as a secondary outcome as well as remifentanil consumption, nausea, vomiting, sedation, corrected QT interval, and quality of life measured with the WHOQOL-BREF questionnaire. A minimum sample size of 78 participants (39 individuals per group) was calculated with a study power of 80% and a confidence level of 95%. After data collection, the analyses will be performed with the support of a statistician using Student’s t-test, chi-square test, Fisher’s exact test, Mann-Whitney test, and analysis of variance (ANOVA), as appropriate. A two-sided p-value <0.05 will be considered statistically significant. Conclusion: This study protocol will inform evidence-based opioid selection and perioperative analgesic strategies safely. No results are yet available.
Keywords
References
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Submitted date:
12/28/2025
Accepted date:
08/21/2026
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