Median effective dose of nefopam to treat postoperative pain in patients who have undergone laparoscopic cholecystectomy

Objective Nefopam is thought to reduce postoperative pain; however, the evidence is insufficient. The recommended dose is 20 mg, and the median effective dose (ED50) in the surgical setting reportedly ranges from 17 to 28 mg. However, nefopam frequently produces inadequate postoperative analgesia. We evaluated the ED50 of nefopam as a single agent in patients undergoing laparoscopic cholecystectomy. Methods Twenty-nine patients were scheduled for laparoscopic cholecystectomy. Postoperative pain was evaluated using a numerical pain scale (NPS). When the NPS score was >3, patients were administered a predetermined dose of nefopam. The dose was calculated using the up-and-down allocation technique based on the previous response. The initial dose was 28 mg, with adjustment intervals of 5 mg. An effective response was defined as a decrease in the NPS score to <3 at 30 minutes after infusion. Results The ED50 of nefopam was 62.1 mg (95% confidence interval, 52.9-72.9 mg). Eight patients reported pain upon injection, and three were excluded due to severe injection pain and phlebitis. Conclusions The estimated ED50 was higher than the predetermined dose based on previous studies. We recommend that the dose of nefopam be chosen after careful consideration of individual variations and clinical settings.