Comparative Evaluation of Gabapentin and Memantine for Postoperative Pain Relief in Laparoscopic Cholecystectomy: Correlation with Pupillary Reflex Dilation Using Pupillometry

Abstract

Background: Effective postoperative pain management is crucial for enhanced recovery after laparoscopic cholecystectomy. Gabapentin and memantine, acting via different mechanisms, may reduce pain and opioid requirements. Pupillometry provides an objective measure of nociception.

Objective: To compare the analgesic efficacy of gabapentin and memantine for postoperative pain relief and correlate pain scores with pupillary reflex dilation.

Methods: In this prospective, randomised, controlled study, 120 patients undergoing elective laparoscopic cholecystectomy were allocated into three groups: gabapentin 900 mg (Group G, n=40), memantine 30 mg (Group M, n=40), and control (Vitamin B-complex, Group C, n=40). Postoperative pain was assessed using the Visual Analogue Scale (VAS) at multiple time points up to 24 hours. Pupillary reflex dilation was measured intraoperatively. Rescue analgesic requirements and adverse effects were recorded.

Results: Both gabapentin and memantine significantly reduced VAS scores and total rescue analgesic use compared to control (p<0.05). Gabapentin showed slightly superior analgesia with earlier onset and longer duration. Pupillometry correlated positively with VAS scores at all time points (Spearman’s r=0.40–0.70, p<0.05). Adverse effects were minimal and comparable between groups.

Conclusion: Preoperative gabapentin and memantine effectively reduce postoperative pain and rescue analgesic consumption, with gabapentin demonstrating slightly greater efficacy. Pupillometry is a reliable objective tool for nociception assessment in perioperative settings.