A total of 78 subjects undergoing gastroscopy/colonoscopy were randomly assigned to the methoxetomidate hydrochloride group and the etomidate group according to the ratio of 1:1:1 with etomidate as the control group, 26 cases in each group. All subjects were blinded to treatment allocation. Screening assessments for all subjects will be completed within D-14 to D-2 before the first dose. For all subjects who received the investigational drug, they were required to return to the research center on D2-5 to complete the corresponding examination before being discharged from the group. To preliminarily evaluate the efficacy and safety of ET-26 in gastroscopy/colonoscopy.

Inclusion Criteria:

1. patients undergoing routine gastroscopy/colonoscopy with an expected gastroscopy/colonoscopy procedure time of less than 20 minutes;
2. age ≥ 18 and ≤ 75 years old, regardless of gender;
3. American Society of Anesthesiologists (ASA) grade I-III;
4. Body mass index (BMI) 18-30 kg/m2 (including the cut-off value) and body weight ≤100 kg;
5. Vital signs during screening: respiratory rate ≥10 and ≤24 times/min; Pulse oxygen saturation (SpO2) ≥95% while breathing air; Systolic blood pressure (SBP) ≥90mmHg and ≤160mmHg; Diastolic blood pressure (DBP) ≥60mmHg and ≤100mmHg; Heart rate (ECG) ≥55 and ≤100 beats/min;
6. Serum cortisol concentration was normal or abnormal but not clinically significant according to the investigator's judgment;
7. Able to understand the procedures and methods of this study, willing to sign the informed consent and strictly abide by the trial protocol to complete the study.

Exclusion Criteria:

1. patients requiring complex endoscopic techniques (such as cholangiopancreatography, endoscopic ultrasonography, endoscopic mucosal resection, endoscopic submucosal dissection, peroral endoscopic myotomy, etc.) or undergoing tracheal intubation;
2. patients with possible gastroduodenal outflow obstruction with retention of contents or upper gastrointestinal bleeding;
3. patients who were known or suspected to have allergies or contraindications to the components of the investigational drug or the prescribed regimen, or who were suspected to have epilepsy or severe liver and kidney dysfunction;
4. predicted difficulty in intubation or ventilation (e.g., modified Mallampti score Ⅲ-Ⅳ, congenital microglossia, mandibular hypoplasia, etc.);
5. having any of the following respiratory management risks before/at the time of screening: 1) history of asthma, wheezing; 2) sleep apnea syndrome;
6. QTcF≥450 ms (male) or ≥470 ms (female) at screening and confirmed by review; Or clinically significant electrocardiographic abnormalities that were deemed by the investigator to be ineligible for the study;
7. use of any of the following drugs or treatments before screening:1) enrolled in a clinical trial of any drug within 1 month before screening; 2) use of medications or treatments that affect cortical function within 3 days before screening; 3) Use of medications that may affect QT interval within 2 weeks before screening;
8. Laboratory tests during the screening period meet the following standards:1)AST and ALT ≥ 3×ULN;2)TBIL≥1.5×ULN;3)hemoglobin ≤90 g/L (and no blood transfusion within 14 days); 4)ANC≤1.5×109/L;5)platelet count ≤80×109/L;6)serum creatinine ≥1.5×ULN;
9. pregnant and lactating women; The reluctance of women or men of childbearing potential to use contraception for the entire dosing period; Subjects (including male subjects) who plan to become pregnant within 3 months after the trial;
10. Subjects with any other factors considered by the investigator to be ineligible for participation in the trial