Study Evaluating the Safety, Efficacy and Pharmacokinetics of SYH9089 Injection in Patients Undergoing Abdominal Surgery.

Inclusion Criteria: * 1\. Fully understand the purpose and significance of this study, voluntarily participate in this study, voluntarily sign the informed consent, and voluntarily abide by the process of this study; 2. 18 years old ≤ age ≤75 years old, regardless of gender; 3. 19.0kg/m2≤BMI≤28.0kg/m2, ≥50.0kg for men and ≥45.0kg for women; 4. American Society of Anesthesiologists (ASA) grade I-II; 5. 5. Elective abdominal surgery under general anesthesia, and the length of the main incision is expected to be between 5-9cm (including the boundary value at both ends); 6. Can understand the research process and the use of various scales involved in this study, and can effectively communicate with researchers. Exclusion Criteria: * 1\. Patients with a history of hypersensitivity to the investigational drug, comparator drug, surgical anesthetics, rescue analgesic drugs, or other drugs that may be used during the trial; 2. Patients with a history of drug abuse/substance use, or those with positive results on a drug abuse screening; 3. Patients with neurological/psychiatric, respiratory, endocrine, hematologic, musculoskeletal, gastrointestinal, cardiovascular systems, or hepatic/renal diseases, judged by the investigator to be unsuitable for the trial; 4. Patients with a history of diabetes mellitus; 5. Patients with a history of myocardial infarction or unstable angina within 1 year prior to randomization; 6. Patients scheduled to undergo purely diagnostic exploratory surgery or palliative tumor resection, judged by the investigator to be unsuitable for the trial; 7. Patients with advanced malignant tumors, judged by the investigator to be unsuitable for the trial; 8. Combined with other pain conditions that may confound the evaluation of postoperative pain according to the investigator; 9. Patients with a history of severe or refractory postoperative nausea or vomiting; 10. Patients scheduled to receive interventions (e.g., intraperitoneal hyperthermic chemotherapy, local/intraperitoneal chemoperfusion, or infrared therapy) during the observation period (randomization to 120h after administration) that may interfere with postoperative pain assessment 11. Use of the following drugs for less than 5 half-lives before randomization (based on the actual drug instructions; or within 7 days prior to randomization if the half-life is unclear) which, in the investigator's judgement, may affect the evaluation of analgesic efficacy. These include, but are not limited to: narcotics (opioids), local anesthetics, non-steroidal anti-inflammatory drugs (NSAIDs), sedative-hypnotics, non-benzodiazepines, sedative anesthetics, glucocorticoids (except for topical use), antiepileptics, anxiolytics, antidepressants, as well as Chinese herbal medicines or proprietary Chinese medicines with sedative or analgesic effects; 12. Use of strong CYP1A2 inhibitors for less than 5 half-lives before randomization (e.g., atazanavir, ciprofloxacin, enoxacin, fluvoxamine, ethinylestradiol) ； 13. Subjects with abnormal findings during the screening period (prior to admission) in vital signs, physical examination, 12-lead ECG, or laboratory tests, which in the investigator's judgement make the subject unsuitable for participation in this trial, including: 1. Patientss with poorly controlled blood pressure despite medication: systolic blood pressure ≥160 mmHg and/or diastolic blood pressure ≥100 mmHg; or systolic blood pressure \<90 mmHg; 2. 12-lead ECG: QTcF ≥450 ms for males or ≥470 ms for females, or a history of severe arrhythmias such as second-degree type II or higher atrioventricular block, or a history of cardiac insufficiency; 3. Coagulation function: PT \> ULN + 3 seconds and/or APTT \> ULN + 10 seconds; 4. Liver function: ALT and/or AST ≥ 2 × ULN; TBIL ≥ 1.5 × ULN; ALB \< 30 g/L; 5. Renal function: Cr ≥ 1.5 × ULN; 6. PLT \< 80 × 10\^9/L; 7. HGB \< 90 g/L; 8. Random blood glucose \> 11.1 mmol/L. 14. Positive for HBsAg, HCV-Ab, HIV-Ab, or TP-Ab;; 15. Female subjects with a positive pregnancy test or who are breast feeding; fertile subjects who plan to become pregnant, are unwilling or unable to use effective contraception during the trial and within 3 months after administration, or who plan to donate sperm or ova; 16. Patients with a history of drug abuse, substance use, and/or alcoholism within 6 months prior to randomization, (alcoholism is defined as alcohol consumption exceeding 14 units per week:1 unit = 360 mL beer, or 45 mL spirits with 40% alcohol content, or 150 mL wine); 17. Patients who underwent major surgery within 3 months prior to randomization, or surgery that may significantly affect the in vivo metabolism of the investigational product or the evaluation of safety; 18. Patients with blood loss or blood donation exceeding 400 mL, or who received blood transfusion or blood products within 3 months prior to randomization; 19. Patients who participated in any clinical trial of drugs or medical devices within 3 months prior to randomization; 20. Any other conditions judged by the investigator to be unsuitable for participation in this trial.