Analogues of etomidate: modifications around etomidate's chiral carbon and the impact on in vitro and in vivo pharmacology

Anesthesiology. 2014 Aug;121(2):290-301. doi: 10.1097/ALN.0000000000000268.


Background: R-etomidate possesses unique desirable properties but potently suppresses adrenocortical function. Consequently, efforts are being made to define structure-activity relationships with the goal of designing analogues with reduced adrenocortical toxicity. The authors explored the pharmacological impact of modifying etomidate's chiral center using R-etomidate, S-etomidate, and two achiral etomidate analogues (cyclopropyl etomidate and dihydrogen etomidate).

Methods: The γ-aminobutyric acid type A receptor modulatory potencies of drugs were assessed in oocyte-expressed α1(L264T)β3γ2L and α1(L264T)β1γ2L γ-aminobutyric acid type A receptors (for each drug, n = 6 oocytes per subtype). In rats, hypnotic potencies and durations of action were measured using a righting reflex assay (n = 26 to 30 doses per drug), and adrenocortical potencies were quantified by using an adrenocorticotropic hormone stimulation test (n = 20 experiments per drug).

Results: All four drugs activated both γ-aminobutyric acid type A receptor subtypes in vitro and produced hypnosis and suppressed adrenocortical function in rats. However, drug potencies in each model ranged by 1 to 2 orders of magnitude. R-etomidate had the highest γ-aminobutyric acid type A receptor modulatory, hypnotic, and adrenocortical inhibitory potencies. Respectively, R-etomidate, S-etomidate, and cyclopropyl etomidate were 27.4-, 18.9-, and 23.5-fold more potent activators of receptors containing β3 subunits than β1 subunits; however, dihydrogen etomidate's subunit selectivity was only 2.48-fold and similar to that of propofol (2.08-fold). S-etomidate was 1/23rd as potent an adrenocortical inhibitor as R-etomidate.

Conclusion: The linkage between the structure of etomidate's chiral center and its pharmacology suggests that altering etomidate's chiral center may be used as part of a strategy to design analogues with more desirable adrenocortical activities and/or subunit selectivities.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adrenal Cortex / drug effects
  • Adrenal Cortex Diseases / chemically induced
  • Adrenal Cortex Diseases / pathology
  • Anesthetics, Intravenous / chemistry*
  • Anesthetics, Intravenous / pharmacology*
  • Anesthetics, Intravenous / toxicity
  • Animals
  • Carbon / chemistry*
  • Etomidate / analogs & derivatives*
  • Etomidate / chemistry
  • Etomidate / pharmacology*
  • Female
  • GABA Agonists / chemical synthesis
  • GABA Agonists / chemistry
  • GABA Agonists / pharmacology
  • Hypnotics and Sedatives / chemical synthesis
  • Hypnotics and Sedatives / chemistry
  • Hypnotics and Sedatives / pharmacology
  • Indicators and Reagents
  • Lethal Dose 50
  • Male
  • Molecular Conformation
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, GABA-A / drug effects
  • Solubility
  • Stereoisomerism
  • Structure-Activity Relationship
  • Xenopus laevis


  • Anesthetics, Intravenous
  • GABA Agonists
  • Hypnotics and Sedatives
  • Indicators and Reagents
  • Receptors, GABA-A
  • Carbon
  • Etomidate