Abstract:Objective To determine the median effective dose（ED50）and 95% effective dose（ED95）of namefene hydrochloride in inhibiting sufentanil - induced cough（SIC）during induction of general anesthesia in children.Methods Thirty-five children［aged 1-6 years，29 males，6 females，body mass（15.2±3.9）kg，American Society of Anesthesiologists physical status I］，scheduled for elective laparoscopic unilateral high ligation of hernial sac under general anesthesia at the Children’s Hospital of Nanjing Medical University from November 2025 to January 2026 were enrolled. Nalmefene hydrochloride was intravenously injected at the start of anesthesia induction with an initial dose of 0.25 μg/kg. Two minutes after the injection，sufentanil 0.3 μg/kg was intravenously administered，followed by propofol 2 mg/kg one minute later. The occurrence of cough was observed. The dose of nalmefene was determined by a modified sequential method：if a positive cough response occurred after sufentanil injection，the next patient’s dose was increased by 0.05 μg/kg；otherwise，it was decreased by 0.05 μg/kg. The study was terminated after eight cross-over points were achieved. The ED50，ED95 and 95% CI of nalmefene for inhibiting SIC during anesthesia induction in children were calculated using Probit regression analysis. Results The ED50 and ED95 of nalmefene in inhibiting SIC during anesthesia induction were 0.087 μg/kg（95% CI：0- 0.168 μg/kg）and 0.283 μg/kg（95% CI：0.187- 2.005 μg/kg），respectively. Conclusion The ED50 and ED95 of nalmefene for prevention of SIC during anesthesia induction in children Fig.1 Sequential diagram of nalmefene inhibiting SIC in children were 0.087 μg/kg and 0.283 μg/kg，respectively. Pretreatment with 0.283 μg/kg of nalmefene hydrochloride can effectively prevent SIC during induction of general anesthesia in children.