Psychomotor Recovery Following Remimazolam-induced Sedation and the Effectiveness of Flumazenil as an Antidote.

Purpose: Remimazolam tosylate (HR-7056) is a novel ester-type benzodiazepine with ultrafast onset of effect. The compound is being developed for sedation induction and maintenance during anesthesia. It was approved for procedural anesthesia in December 2019 by the National Medical Products Administration of China. Previous studies have reported on remimazolam's effects on consciousness and cognition. Although the time to full psychomotor recovery after remimazolam-mediated sedation is critical for decisions regarding hospital discharge, relevant clinical evidence is still lacking. This study investigated the residual psychomotor effects of remimazolam and their recovery from sedating treatment in 2 simulated clinical settings: (1) single-dose administration for sedation initiation; and (2) constant rate infusion for sedation maintenance.

Methods: A single-ascending-dose, parallel-group, midazolam-controlled study and a 2-way crossover study evaluating the reversal effect of flumazenil versus placebo after a 2-h constant rate infusion were conducted with HR-7056 in 87 Chinese healthy volunteers; the studies used a double-blind, randomized trial design. A battery of psychomotor tests was administered before dosing and several times postdose over 4-6 h. Pharmacokinetic, sedation, and safety assessments were performed throughout the studies.

Findings: After bolus infusion, the Bispectral Index score decreased in a concentration-dependent manner with HR-7056, accompanied by a sharp drop of Modified Observer's Assessment of Alertness/Sedation score. The recovery of consciousness was much faster with HR-7056 than with midazolam. During the constant rate infusion, the Bispectral Index score was maintained between 40 and 60 with an average plasma remimazolam concentration of ~1000 ng/mL. Subjects' performance in saccadic and smooth pursuit eye movement, body sway, test of choice reaction time, and word recall was significantly impaired after single-dose midazolam and after constant rate infusion of remimazolam. The end-of-infusion injection of flumazenil shortened the median time to full alertness to 3.5 min and effectively reversed psychomotor and cardiovascular dysfunction.

Implications: The study results showed quicker psychomotor recovery from sedation in the remimazolam-treated group. The moderate and short-lasting residual effect of remimazolam after 2-h conscious sedation proposes a need for psychomotor assessment(s) before hospital discharge. ClinicalTrials.gov identifiers: NCT01970072 and NCT03444480.