Evaluation of anesthetic effects of remimazolam using mouse model with jugular vein cannulation

OBJECTIVE: Remimazolam, a novel ultra-short-acting benzodiazepine anesthetic, provides rapid recovery with minimal circulatory depression, making it a promising agent for procedural sedation. However, differences in regulatory approvals and safety requirements across countries limit its clinical use. Therefore, its pharmacological properties and safety should be clarified in further studies. In this study, jugular vein-cannulated model mice were administered intravenous anesthetic, and the sedative effects of remimazolam were compared with those of midazolam and propofol. METHODS: Following jugular vein cannulation, each mouse was administered a single intravenous dose of remimazolam or midazolam, and changes in sedation levels were assessed using a sedation scale. In another test, continuous infusion of propofol or remimazolam was administered using a precise microflow pump and sedation scale scores, defensive reflexes, and vital signs were analyzed. RESULTS: The sedation scale score increased after a single administration of remimazolam or midazolam in a concentration-dependent manner, followed by gradual recovery, whereas continuous administration caused a gradual increase that stabilized over time. Continuous remimazolam administration (30 mg/kg/h) produced sedation comparable to that produced by propofol administration (120 mg/kg/h), although with much smaller decreases in heart and breathing rates. Defensive reflex reactivity in mice administered remimazolam exhibited a shorter time to reflex extinction than in those administered propofol, with repeated extinction and recovery cycles. CONCLUSIONS: Our findings suggest that the jugular vein-cannulated mouse model is useful for evaluating time-dependent sedative effects. Continuous remimazolam administrationmaintained stable sedation with minimal vital depression and faster defensive reflex suppression than propofol administration.