Pharmacological profiles and mechanism of action of remimazolam for ICU sedation

TL;DR

This paper explores remimazolam, a short-acting benzodiazepine, as a potential alternative for ICU sedation, highlighting its metabolism, effects, and dosing considerations.

Contribution

The paper provides a detailed pharmacological and mechanistic analysis of remimazolam for ICU sedation, including its metabolism and patient-specific dosing factors.

Findings

Remimazolam is rapidly metabolized by carboxylesterase 1 in the liver, not in the blood.

The drug accumulates during prolonged infusions, leading to delayed emergence and requiring dose adjustments based on patient characteristics.

Remimazolam shows a 10-20% higher steady-state concentration in males, obese patients, and those with higher ASA physical status.

Abstract

Remimazolam, a benzodiazepine, was first approved in 2020 for general anesthesia and procedural sedation but has not for sedation in the intensive care units. As other sedatives used in intensive care units have disadvantages such as propofol infusion syndrome and hypotension, an alternative sedative would be desired.

Remimazolam was developed as a soft drug that is designed to be rapidly metabolized to the inactive chemical, CNS7054. In humans, it is mainly metabolized by the non-specific esterase, carboxylesterase 1, in the liver, not in the blood, unlike the ultrashort-acting soft drug remifentanil. Remimazolam is a short-acting drug. The context-sensitive decrement time, which describes how the accumulated drug affects the decay curve of the drug concentration after its infusion ends, of remimazolam is similar to that of propofol. Remimazolam binds the benzodiazepine site of the gamma-aminobutyric acid type A receptors, and does not directly activate the gamma-aminobutyric acid type A receptors. Benzodiazepines are not effective in the absence of gamma-aminobutyric acid. Although hypotension appears less frequent, it can occur during remimazolam administration. Delayed emergence can occur after remimazolam infusion due to its accumulation. To prevent delayed emergence, excessive doses should be avoided. A dose of the competitive antagonist flumazenil can cause re-sedation after administration. The impact of delirium after prolonged sedation is unknown. The remimazolam concentration at steady-state is approximately 10% higher in males than in females, > 20% in obese patients than in normal weight patients, and approximately 20% higher in American Society of Anesthesiologists physical status III/IV patients than in I/II patients. The infusion rate should may be reduced in these patients. A study has shown that the required dose is higher in children than in adults.

Remimazolam could be an alternative sedative in intensive care units. Because remimazolam is short-acting, it accumulates during prolonged infusions. Infusion rate should be titrated based on patient characteristics, including sex, body mass index, and physical status. Benzodiazepine tolerance should be considered before and during remimazolam infusion. Similar to other sedatives, concurrent use of additional hypnotics and analgesics may help maintain the desired sedation in intensive care units.

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