A double-blind, randomized, active controlled, multi-center, parallel group study comparing HSK3486 with Propofol, in patients undergoing a colonoscopy.

Inclusion Criteria:

1. Scheduled to undergo a diagnostic or therapeutic colonoscopy;
2. Male or female patients, ASA grade I~III, aged ≥ 18 and≤ 70;
3. Body mass index (BMI) ≥ 18 and ≤ 30 kg/m2;
4. the respiratory rate ≥10 and ≤24, SpO2 when inhaling ≥95%, SBP≥90mmHg, DBP≥60mmHg, HR≥55and ≤100;
5. Patient can understand the procedure of this study and is willing to comply with study requirements. The patient can sign the ICF voluntarily.

Exclusion Criteria:

1. Patients were contraindicated in general anesthesia.
2. Patients with a known sensitivity to propofol, opioids, naloxone, eggs, soy products or a medical condition such that these agents were contraindicated.
3. The patient has some history or evidence of increased risk of sedation or anesthesia, such as cardiovascular disease, respiratory disease, cerebrovascular disease, gastrodintestinal disease and other system disease prior to the screening and/or baseline period.
4. Patients with a history of drug or ethanol abuse with the past 3 months.
5. Patients with respiratory management difficulties.
6. Patients in receipt of any investigational drug within 30 days before screening.
7. Patients in receipt of propofol, opioid , other sedative or anesthetic or analgesics within 72 hours before screening.
8. Abnormal laboratory results consisting of any of the following:

1) neutrophil count≤ 1.5×109/L； 2）platelet≤ 80×109/L； 3）hemoglobin≤ 90 g/L; 4）aspartate aminotransferase≥ 1.5×ULN； 5) serum creatinine≥ 1.2×ULN. 9. Pregnant women or female patients with a positive serum or urine human chorionic gonadotropin pregnancy test at screening or baseline or lactating female patients.

10. Patients with an inability to communicate well with the investigator, or deemed unsuitable according to the investigator (in each case providing a reason)