EXPLANATION

Remimazolam is an ultra-short-acting, rapid onset benzodiazepine that was approved in 2020 for use in adults undergoing procedural sedation in the United States. Its favorable pharmacological profile combined with its hemodynamic stability make it an attractive sedative, particularly in medically complex patients^1,2. Limited widespread population studies and cost may be current limitations to practical adaptation into clinical practice, but nonetheless its use is likely to increase as it becomes more widely available.

Like other benzodiazepines, remimazolam is a GABA_A agonist, leading to increased frequency of opening of chloride ion channels. This results in hyperpolarization and inhibition of neural activity. Onset of action is within 60 seconds, with peak effect around 3 to 4 minutes, and a typical duration of action of 11-14 minutes in healthy controls^1,2. It has a low volume of distribution and mean distribution half-life (t_1/2) of 0.5-2 minutes. It is rapidly hydrolyzed to a pharmacologically inactive metabolite via tissue esterase activity, primarily liver carboxylesterase CES1 (answer B) and excreted in urine^1,2. These properties lead to fast onset and offset of sedation and predictable duration of action. CYP3A4 is associated with midazolam metabolism¹. Non-specific esterases hydrolyze medications such as remifentanil^1,2. And Hoffman elimination is non-enzymatic degradation associated with cisatracurium.

Notably, pharmacokinetic properties were not significantly altered in elderly patients, those with end-stage renal dysfunction, or mild to moderate hepatic dysfunction. There was, however, lower clearance in patients with severe hepatic impairment, suggesting that dose adjustment may be recommended. Further studies are needed in larger populations. Adverse effects include changes to heart rate and blood pressure, nausea, dizziness, and headaches. Similar to other benzodiazepines, flumazenil can be used to reverse the effects of remimazolam^2,3.

Preparation is in a 20mg powdered vial and should be dissolved in 8.2mL of 0.9% sodium chloride, resulting in a 2.5mg/mL final concentration once reconstituted. A precipitate will form if remimazolam is dissolved in Lactated Ringer’s solution². Typical dosing involves a 5 milligram (mg) bolus administered intravenously over 1 minute. Supplemental doses of 2.5mg can be given, with at least 2 minutes between doses. While not FDA-approved for general anesthesia, studies investigating the role of remimazolam in total intravenous anesthesia (TIVA) are ongoing. Suggested doses are 0.2-0.4mg/kg on induction followed by 1-2mg/kg/hr as a maintenance infusion². Small scale studies have suggested superiority with regards to hemodynamic stability during TIVA, but there was no major difference in time to emergence and extubation compared to propofol³.

Remimazolam is not yet FDA-approved for use in pediatric patients and most studies to date have been completed in the adult population. Early pediatric studies suggest similar pharmacokinetics, but further investigation is needed to assess pediatric dosing and application to specific procedures. Use in patients with mitochondrial diseases may be of particular interest, where caution with propofol and volatile agents is advised⁴.

Remimazolam has been most extensively studied in endoscopy. Compared with propofol, a recent meta-analysis demonstrated similar times of induction and return to neurologic baseline, but less hypotension and respiratory depression requiring treatment in the remimazolam group³. Given its favorable pharmacologic properties and improved safety profile, remimazolam may play an important role in sedation for medically fragile patients undergoing sedation for short procedures.

REFERENCES

1. Kim KM. Remimazolam: pharmacological characteristics and clinical applications in anesthesiology. Anesth Pain Med 2022;17(1):1-11

2. Abcejo AS., Teixeira MT. Remimazolam: patient safety considerations of a novel, practice-changing drug in perioperative medicine. APSF Newsletter 2023;38:80–83.

3. Barbosa EC., Espírito Santo PA., Baraldo S., et al. Remimazolam versus propofol for sedation in gastrointestinal endoscopic procedures: a systematic review and meta-analysis. Br J Anaesth. 2024 Jun;132(6):1219-1229

4. Aszkiełowicz A, Kapłan C, Kapica P, et al. Remimazolam: a comprehensive review. Anaesthesiol Intensive Ther. 2025 Oct 1;57(1):257-266