Pharmacology
Pharmacodynamics
(R)-Etomidate is tenfold more potent than its (S)-enantiomer. At low concentrations (R)-etomidate is a modulator at GABAA receptors containing β2 and β3 subunits. At higher concentrations, it can elicit currents in the absence of GABA and behaves as an allosteric agonist. Its binding site is located in the transmembrane section of this receptor between the beta and alpha subunits (β+α−). β3-containing GABAA receptors are involved in the anesthetic actions of etomidate, while the β2-containing receptors are involved in some of the sedation and other actions that can be elicited by this drug. Pharmacokinetics
At the typical dose, anesthesia is induced for the duration of about 5–10 minutes, though the half-life of drug metabolism is about 75 minutes, because etomidate is redistributed from the plasma to other tissues. Onset of action: 30–60 seconds
Peak effect: 1 minute
Duration: 3–5 minutes; terminated by redistribution
Distribution: Vd: 2–4.5 L/kg
Protein binding: 76%
Metabolism: Hepatic and plasma esterases
Half-life distribution: 2.7 minutes
Half-life redistribution: 29 minutes
Half-life elimination: 2.9 to 5.3 hours

Metabolism
Etomidate is highly protein-bound in blood plasma and is metabolised by hepatic and plasma esterases to inactive products. It exhibits a biexponential decline. Formulation
Etomidate is usually presented as a clear colourless solution for injection containing 2 mg/ml of etomidate in an aqueous solution of 35% propylene glycol, although a lipid emulsion preparation (of equivalent strength) has also been introduced. Etomidate was originally formulated as a racemic mixture, but the R form is substantially more active than its enantiomer. It was later reformulated as a single-enantiomer drug, becoming the first general anesthetic in that class to be used clinically.
Using a continuous etomidate infusion for sedation of critically ill trauma patients in intensive care units has been associated with increased mortality due to adrenal suppression. Continuous intravenous administration of etomidate leads to adrenocortical dysfunction. The mortality of patients exposed to a continuous infusion of etomidate for more than 5 days increased from 25% to 44%, mainly due to infectious causes such as pneumonia.Because of etomidate-induced adrenal suppression, its use for patients with sepsis is controversial. Cortisol levels have been reported to be suppressed up to 72 hours after a single bolus of etomidate in this population at risk for adrenal insufficiency. For this reason, many authors have suggested that etomidate should never be used for critically ill patients with septic shock because it could increase mortality. However, other authors continue to defend etomidates use for septic patients because of etomidates safe hemodynamic profile and lack of clear evidence of harm. A study by Jabre et al. showed that a single dose of etomidate used for Rapid Sequence Induction prior to endrotracheal intubation has no effect on mortality compared to ketamine even though etomidate did cause transient adrenal suppression. In addition, a recent meta-analysis done by Hohl could not conclude that etomidate increased mortality. The authors of this meta-analysis concluded more studies were needed because of lack of statistical power to conclude definitively about the effect of etomidate on mortality. Thus, Hohl suggests a burden to prove etomidate is safe for use in septic patients, and more research is needed before it is used.