STUDY OBJECTIVE: To investigate whether melatonin administered intraoperatively reduced pain following laparoscopic cholecystectomy.

DESIGN: Randomized, placebo-controlled, double-blinded study.

SETTING: Two surgical departments in Copenhagen.

PATIENTS: 44 women between 18 and 70 years of age, who were surgical candidates for laparoscopic cholecystectomy.

INTERVENTIONS: Patients were anesthetized by a standard protocol and received a standard multimodal postoperative analgesic regimen. Patients undergoing surgery were admitted on the day of surgery and were discharged the day after surgery. Ten mg of intravenous (IV) melatonin or placebo were administered at the time of surgical incision.

MEASUREMENTS: Pain was assessed by a set of questionnaires documenting "pain at rest" using a visual analog scale (VAS). The use of rescue medication was recorded. Sleep quality and general well-being were measured on separate VAS scales. Sleepiness was assessed by the Karolinska Sleepiness Scale.

MAIN RESULTS: Forty-four patients were included and randomized to the study. Three patients did not complete the study. No differences in VAS pain scores, sleep quality, general well-being, or sleepiness were found between the two groups in the postoperative period. The use of postoperative rescue medication did not differ between the groups.

CONCLUSIONS: The use of 10mg of IV melatonin administered during laparoscopic cholecystectomy did not affect postoperative pain or use of analgesic medication.