Osemitidine fumarate is a novel G protein-biased ligand μ-opioid receptor agonist. Previous studies have confirmed its potent analgesic effects and safety: compared with morphine, it reduces respiratory depression and gastrointestinal dysfunction. This study aims to evaluate the effects of osemitidine on postoperative gastrointestinal function recovery and pain in patients undergoing lumbar spine surgery through a multicenter, double-blind, randomized controlled trial.

Inclusion Criteria:

• Age between 18 and 75 years old;
• Patients undergoing lumbar surgery under general anesthesia (within 3 segments) and expected to receive postoperative patient-controlled analgesia;
• ASA classification I-III;
• BMI between 18 and 30 kg/m²;
• Informed consent obtained from the patient.

Exclusion Criteria:

• Use of any painkillers within 3 days before surgery; or long-term treatment with non-steroidal anti-inflammatory drugs (NSAIDs), defined as: within 3 months before surgery, use of NSAIDs daily for more than 2 consecutive weeks;
• Presence of intestinal obstruction or suspicious symptoms: nausea and vomiting, abdominal bloating and pain, cessation of gas or bowel movements within the past two weeks, imaging suggesting intestinal dilation, or large amounts of air-fluid levels;
• Patients with severe liver dysfunction (based on Child-Pugh classification, grade C);
• History of or planned gastrointestinal surgery;
• Patients allergic to the study drug;
• Pregnant or breastfeeding patients;
• QTcF abnormalities, males >450 ms, females >470 ms;
• Participation in other drug trials within the past 30 days;
• Long-term use of opioids (defined as: within 12 months before surgery, use for more than 1 month, more than 3 days per week, with daily doses exceeding 15 mg morphine equivalent);
• Pre-existing neurological or psychiatric disorders: such as epilepsy, depression, schizophrenia, etc.;
• Patients deemed unsuitable for this study by the investigator.