Dixon Up-and-Down Method for Optimizing Oxycodone Dosage in Painless Colonoscopy

Yujie Ding,1,* Chunliu Hou,2,* Yan Li1– 3 1Institute of Traditional Chinese Medicine, Tianjin University of Traditional Chinese Medicine, Tianjin, 301617, People’s Republic of China; 2Department of Anesthesiology, Tianjin Medical University, Tianjin, 300070, People’s Republic of China; 3Department of Anesthesiology, Tianjin Jizhou District People’s Hospital (Fifth Teaching Hospital of Tianjin University of Traditional Chinese Medicine), Tianjin, 301900, People’s Republic of China*These authors contributed equally to this workCorrespondence: Yan Li, Department of Anesthesiology, Tianjin Jizhou District People’s Hospital (Fifth Teaching Hospital of Tianjin University of Traditional Chinese Medicine), Tianjin, 301900, People’s Republic of China, Email drliyanteam@163.comAim: Inadequate analgesia during painless colonoscopy can result in undesirable body movements, undermining patient safety and procedural success. Oxycodone, known for its dual κ- and μ-receptor agonism, may provide effective analgesia with a reduced incidence of adverse effects compared to other opioids. However, the optimal intravenous dose of oxycodone for suppressing body movement during colonoscopy has not been established.Methods: This prospective, single-center, dose-finding study enrolled adult patients scheduled for painless colonoscopy. All participants received intravenous oxycodone in combination with propofol, with the oxycodone dose determined according to the Dixon and Massey up-and-down sequential allocation method. The primary outcome was the median effective dose (ED50) of oxycodone required to suppress body movement during colonoscope insertion. Body movement was graded, and a positive response was defined as movement graded ≥ 2. The ED50 was estimated as the mean of crossover midpoints after at least seven reversal pairs, and the 95% confidence interval (CI) was determined by probit regression. Adverse events within 20 minutes after the procedure, including agitation, abdominal pain, nausea or vomiting, dizziness or headache, and postural instability, were also recorded.Results: A total of 36 patients were enrolled. The calculated ED50 of oxycodone for suppression of body movement during colonoscope insertion was 0.055 mg/kg, 95% CI: 0.047– 0.063 mg/kg.Conclusion: Intravenous oxycodone, when dosed by the Dixon up-and-down method, is effective and safe for analgesia during painless colonoscopy.Clinical Trial Registration: ChiCTR:ChiCTR2300077446.Keywords: oxycodone, painless colonoscopy, up-and-down method, median effective dose, ED50, analgesia