INTRODUCTION Morbid obese patients have different pharmacodynamic and pharmacokinetic as compared to normal weight individuals. 1 These patients have low pain threshold. 2 Management of postoperative pain in obese patients is always a challenge. Laparoscopic sleeve gastrectomy is an effective surgical procedure in facilitating the patient weight loss and preventing the serious future health complications. Laparoscopic sleeve gastrectomy causes moderate to severe postoperative pain. 3 Caution is always warranted when analgesics, opioids, are used in obese patients, especially in the postoperative period. Different types of surgeries cause different types and severity of pain and postoperative analgesic requirement. 4 Multiple modal analgesia is recommended in obese patients for the reduction of opioid consumption and its side effects. 5 Gabapentin as a multimodal analgesic and pain modulator has been extensively studied for many surgical procedures and found to be having post- operative opioid sparing effect and improved pain scores. 6 Gabapentin inhibits the calcium influx to A and C neurons reducing excitatory neurotransmitter release from the dorsal horn and thereby inhibiting nociception. 5 However, in literature the effectiveness of preoperative administration of gabapentin for postoperative pain and opioid sparing effect showed varying results in different types of surgeries. The effectiveness of gabapentin in a particular surgical intervention is difficult to predict. The evidence regarding the effect of gabapentin on post- operative pain and opioid sparing effect in morbidly obese patients is sparse. Gabapentin is also known to be effective for the treatment of generalised anxiety disorders. However, in literature mixed results were reported regarding its effectiveness for the reduction of preoperative anxiety. It was hypothesised that pre- operative administration of an anticonvulsant drug, gabapentin, could be helpful to optimise the post- operative pain, opioid requirement and preoperative anxiety in obese patients undergoing laparoscopic sleeve gastrectomy. The objective of this study was to determine the effective- ness of gabapentin for the reduction of acute post- operative pain, morphine consumption and preoperative Journal of the College of Physicians and Surgeons Pakistan 2019, Vol. 29 (8): 697-701 697 ORIGINAL ARTICLE The Effect of Gabapentin on Postoperative Pain, Morphine Sparing Effect and Preoperative Anxiety in Patients Going for Sleeve Gastrectomy Surgical Procedure Mueen Ullah Khan 1 , Fahad Y. Bamehriz 2 , Mansoor Aqil 1 , Fatama Al Dammas 1 , Awatif Fadin 1 and Rashid Saeed Khokhar 1 ABSTRACT Objective: To determine the effectiveness of preoperative administration of gabapentin in reduction of acute postoperative pain, morphine consumption and preoperative anxiety and sedation in obese patients undergoing laparoscopic sleeve gastrectomy. Study Design: Double-blinded randomised control trial. Place and Duration of Study: King Khalid University Hospital, King Saud University Riyadh, Saudi Arabia, from July 2014 to January 2017. Methodology: Fifty patients undergoing sleeve gastrectomy were enrolled in the study. The subjects received either 1200 mg gabapentin or placebo 2 hours before surgery. The amount of morphine consumption and postoperative pain at 4, 8,12,16, 20 and 24 hours of surgery were measured. Preoperative anxiety and sedation were recorded at 2 hours interval after the drug administration. Results: There was no significant difference in patient characteristics in both groups. 24 hours PCA morphine consumption was significantly lower in gabapentin group than in the placebo group, 15.08 ±4.55 vs. 27.80 ±2.51 (p=0.001). Preoperative VAS anxiety, pre- verses post-drug, was significantly lower in gabapentin group 5.80 ±1.11 vs. 3.52 ±1.00 (p=0.001) than in placebo group 6.08 1.28 vs. 6.28 1.24 (p=0.635). Preoperative sedation score was not different in both groups. Conclusion: Preoperative oral gabapentin was effective in reducing the postoperative pain, morphine consumption and preoperative anxiety in morbid obese patients undergone laparoscopic sleeve gastrectomy. Key Words: Obesity-morbid, Gabapentin, Postoperative pain, Analgesic opioid, Preoperative anxiety, Laparoscopic sleeve gastrectomy. Department of Anesthesia 1 / Surgery 2 , King Khalid University Hospital College of Medicine, King Saud University, Riyadh, Saudi Arabia Correspondence: Dr. Mueen Ullah Khan, Department of Anesthesiology, King Khalid University Hospital, College of Medicine, King Saud University, P.O Box 7805, Riyadh 11472, Saudi Arabia E-mail: mueenullahpk@hotmail.com Received: September 04, 2018; Revised: February 26, 2019; Accepted: April 22, 2019