This is a Phase II, dose-escalation clinical trial conducted in mechanically ventilated patients receiving sedation no longer than 24 hours. The efficacy, safety, and pharmacokinetics of remimazolam besylate were evaluated using a randomized, single-blind design.

Inclusion Criteria:

• Body mass index (BMI) ≥18 and ≤ 30 kg/m2
• Being Intubated and mechanically ventilated ≤48 hours before enrollment and expected to be on a ventilator for at least 6 hours
• Requirement for light to moderate sedation (a Richmond agitation-sedation scale score of -2 to 1)

Exclusion Criteria:

• Refusal to be included
• Allergy or unsuitability to any composition of study drugs or remifentanil
• Living expectancy less than 48 hours
• Myasthenia gravis
• Status asthmaticus
• Abdominal compartment syndrome
• Serious hepatic dysfunction (CTP 10-15);
• Chronic kidney disease with glomerular filtration rate (GFR) < 29 ml/min/1.73m2
• Mean blood pressure less than 65 mm Hg or the need for a continuous infusion of norepinephrine at ≥0.5 ug/kg/min to maintain Mean blood pressure ≥ 65 mm Hg
• Possible requirement for surgery or bedside tracheostomy in 24 hours
• Possible requirement for renal replacement therapy in 24 hours
• Acute severe neurological disorder and any other condition interfering with sedation assessment
• Abuse of controlled substances or alcohol
• Pregnancy or lactation