Background: Nefopam and propacetamol are the most commonly used analgesics in postoperative multimodal analgesic regimens. Distinct mechanisms are involved in each drug's anti-nociceptive effects. No studies have compared pain relief efficacy between the two drugs in patients undergoing transplantation surgery. Here, we investigated whether the administration of nefopam or propacetamol to healthy living kidney donors who underwent rectus sheath block (RSB) for parietal pain could reduce the subsequent opioid dose necessary to produce adequate analgesia.

Methods: This prospective, randomized controlled trial included 72 donors undergoing elective hand-assisted living donor nephrectomy into two groups: propacetamol (n = 36) and nefopam (n = 36). Intraoperative RSB was performed in all enrolled donors. The primary outcome was the total volume of intravenous opioid-based patient-controlled analgesia (PCA) used on postoperative day 1 (POD 1). Additionally, the Numeric Rating Scale scores for flank (visceral) and umbilicus (parietal) pain at rest and during coughing were compared, and the Korean adaptation of the Quality of Recovery-15 Questionnaire (QoR-15 K) was evaluated on POD 1.

Results: Both groups had similar preoperative and intraoperative characteristics. On POD 1, the total amount of PCA infusion was significantly lower in the nefopam group than in the propacetamol group (44.5 ± 19.3 mL vs. 70.2 ± 29.0 mL; p < 0.001). This group also reported lower pain scores at the flank and umbilical sites and required fewer rescue doses of fentanyl in the post-anesthesia care unit. However, pain scores and fentanyl consumption in the ward were comparable between groups. The QoR-15 K scores were similar between groups; there were substantial improvements in breathing, pain severity, and anxiety/depression levels in the nefopam group. The incidences of postoperative complications, including sweating and tachycardia, were similar between groups.

Conclusion: Compared with propacetamol, nefopam provides a greater analgesic effect for visceral pain and enhances the effects of blocks that reduce the opioid requirement in living kidney donors with parietal pain managed by RSB.

Trial registration: The trial was registered prior to patient enrollment in the clinical trial database using the Clinical Research Information Service (registration no. KCT0007351 , Date of registration 03/06/2022).