Remimazolam is an ultra–short-acting benzodiazepine currently being developed for procedural sedation and for induction and maintenance of anesthesia. This trial was the fourth study for procedural sedation. The aim was to compare the safety and efficacy profile of remimazolam and to refine suitable doses for subsequent phase III studies in this indication.

This was a randomized, double-blind, parallel group, active controlled clinical trial with 162 male and female patients, aged 18 to 70, scheduled to undergo a routine colonoscopy. Patients were randomized to receive 1 of 3 remimazolam doses or midazolam for sedation. Supplemental oxygen and 100 μg of fentanyl was given before procedures were started, and the colonoscopy commenced as soon as suitable sedation had been achieved (Modified Observer's Assessment of Alertness/Sedation score ≤3). Top-up doses of the study drug and/or fentanyl were allowed to maintain suitable sedation and/or analgesia. Response was defined as sufficient sedation, no rescue sedative, and no ventilation required.

This study showed that a single dose of remimazolam or midazolam, followed by top-up doses to maintain suitable sedation, provided adequate sedation with a high success rate (>92%) for the remimazolam groups, compared with 75% for the midazolam group (P = .007). There was no requirement for mechanical ventilation in any group, and procedure failures were all due to use of rescue sedative.

The high success rates and good safety profile of remimazolam observed in this study warrants further investigation and confirmation in phase III trials. (Clinical trial registration number: NCT01145222.)