Anrikefon Injection for Postoperative Analgesia in Thoracoscopic Lung Surgery: A Randomized, Double-Blind, Active-Controlled, Parallel-Group, Single-Center Clinical Study

Inclusion Criteria:

1. Age 18 to 85 years (inclusive), either sex.
2. Body mass index (BMI) 18.0 to 30.0 kg/m² (inclusive).
3. American Society of Anesthesiologists (ASA) physical status Class I to III preoperatively.
4. Undergoing elective thoracoscopic lung surgery under general anesthesia (complete video-assisted thoracoscopic surgery, without conversion to thoracotomy), with successful recovery from anesthesia within 1 hour postoperatively, fully awake, able to accurately complete NRS scoring with an NRS score ≥ 4, and willing to accept the analgesic regimen defined in the study protocol.
5. Able to understand the purpose, procedures, and scale scoring methods of the study, capable of operating the PCA device, and able to communicate effectively with investigators.
6. Voluntarily participating and providing written informed consent.

Exclusion Criteria:

1. Known or suspected allergy or contraindication to any of the study drugs.
2. History of opioid abuse, drug or alcohol dependence, or current preoperative use of opioids.
3. Use of analgesic medications (acetaminophen, NSAIDs, opioids, tramadol, etc.) within 24 hours preoperatively.
4. Uncontrolled severe cardiovascular disease (second-degree or higher atrioventricular block, resting heart rate < 50 bpm, uncontrolled hypertension, myocardial infarction or unstable angina within the past 6 months), hepatic insufficiency (ALT/AST > 2× upper limit of normal), renal insufficiency (eGFR < 30 mL/min/1.73m² or maintenance dialysis), neuropsychiatric dysfunction, or inability to cooperate with pain assessment.
5. History of chronic pain.
6. Severe respiratory or circulatory failure during anesthesia/surgery (including intraoperative conversion to thoracotomy, operative time > 6 hours, or intraoperative hemorrhage > 1000 mL).
7. Pregnancy or lactation, or positive urine pregnancy test in women of childbearing potential.
8. Participation in another drug/device clinical trial within 30 days before randomization.
9. Any other condition that the investigator deems unsuitable for participation.