after joining the study you are assigned to one of three groups: patient‑controlled sedation with remimazolam, physician‑controlled sedation with remimazolam, or physician‑controlled sedation with midazolam. the assignment is done by the study system and you are not required to choose.

you receive an alfentanil injection of 5 mg. alfentanil is an opioid medication that helps control pain during the procedure.

depending on the group to which you were assigned, one of the following occurs:

patient‑controlled sedation with remimazolam: you use a handheld device to give yourself a 50 mg injection of remimazolam as needed during the colonoscopy.

physician‑controlled sedation with remimazolam: the physician gives you a single 50 mg injection of remimazolam at the start of the procedure.

comparator group (physician‑controlled midazolam): the physician gives you a single 10 mg injection of midazolam at the start of the procedure.

the dose is administered as a single injection before the colonoscopy begins; additional doses may be given only if required by the physician.

you lie on a table while the endoscopist performs the colonoscopy. the sedation you received keeps you comfortable and may cause limited awareness.

clinical staff continuously monitor your heart rate, breathing, and level of consciousness throughout the procedure.

they watch for any moderate or severe adverse events (undesired medical problems) and are prepared to intervene if needed.

after the colonoscopy you are moved to a recovery area where you are observed until you meet the criteria for safe discharge (stable vital signs, ability to sit up, and clear thinking).

the goal is to achieve discharge without unnecessary delay.

once you are ready to leave, you complete a short questionnaire that measures your overall satisfaction with the sedation experience.