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

Inclusion Criteria (those who meet all of the following are eligible)

1. Patients requiring diagnostic colonoscopy with an estimated examination time ≤ 30 min; males and females, ASA grade I-II, between 18 and 65 years old (inclusive);
2. Body mass index (BMI) ≥ 18 and ≤ 30 kg/m2
3. Respiratory rate between ≥ 10 and ≤ 24 breaths per minute; SpO2 when inhaling > 95%; SBP ≥ 90 mmHg; DBP ≥ 60 mmHg; heart rate between ≥ 50 and ≤ 100 beats per minute;
4. Subjects must understand the procedures and methods of this study, and be willing to provide informed consent and to complete the trial in strict accordance with clinical trial protocol.

Exclusion Criteria (those who meet any one of the following are ineligible):

1. Patients having contraindications to general anesthesia or previous history of anesthesia accidents;

2. Patients with a known sensitivity to propofol, opioids, naloxone, eggs, soy products or a medical condition such that these agents were contraindicated;

3. Patient received any of the following drugs or therapies prior to screening:

   1. Participated in other drug clinical trials within 3 month prior to screening;
   2. In receipt of propofol and/or opioid analgesics within 1 month prior to screening;

4. 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.

5. Patient whose laboratory parameters measured at screening/prior to enrollment reach the following criteria and verified through re-examinations:

   1. ANC ≤ 1.5 x 109/L;
   2. PLT ≤ 80 x 109/L;
   3. Hb ≤ 90 g/L (no blood transfusion within the last 14 days);
   4. AST and ALT ≥ 2.5 x ULN;
   5. TBIL ≥ 1.5 x ULN;
   6. Creatinine ≥ 1.5 x ULN.

6. History of alcohol abuse within 3 months prior to screening or with a positive result of alcohol saliva strip test (before dose);

7. History of medication abuse within 3 months prior to screening, or a positive urine medication test (during screening or before dose administration);

8. Women who are pregnant or breastfeeding; women of child-bearing potential or men who are unwilling to use contraception during the trial; Patients who are planning pregnancy within 1 month after the completion of the trial (including male patients);

9. Potential difficult airway or difficult tracheal intubation, as determined by the investigator, and/or history of intubation failure;

10. Patients determined by the investigator to be unsuitable for participating in this trial for any reason.