Etomidate (AMIDATE®) is an imidazole derivative anesthetic and hypnotic with little effect on blood gases, ventilation, or the cardiovascular system. It is intended for the induction of general anesthesia by intravenous injection. Etomidate (AMIDATE®) is also indicated for the supplementation of subpotent anesthetic agents, such as nitrous oxide in oxygen, during maintenance of anesthesia for short operative procedures such as dilation and curettage or cervical conization. It also produces a unique toxicity among anesthetic drugs - inhibition of adrenal steroid synthesis that far outlasts its hypnotic action and that may reduce survival of critically ill patients. The major molecular targets mediating anesthetic effects of etomidate (AMIDATE®) in the central nervous system are specific gamma-aminobutyric acid (GABA) type A receptor subtypes. The R(+) isomer of etomidate is 10 times more potent than its S(-) isomer at potentiating GABA-A receptor activity.

Isoflurane (1-chloro-2, 2,2-trifluoroethyl difluoromethyl ether) a nonflammable liquid administered by vaporizing, is a general inhalation anesthetic drug. Isoflurane is a clear, colorless, stable liquid containing no additives or chemical stabilizers. Similar to many general anesthetics, the exact mechanism of the action has not been clearly delineated. Isoflurane reduces pain sensitivity (analgesia) and relaxes muscles. Isoflurane likely potentiates GABA-A and glycine receptor activity, which decreases motor function, inhibits receptor activity in the NMDA glutamate receptor subtypes and binds to glutamate receptors. Isoflurane is always administered in conjunction with air and/or pure oxygen. Often nitrous oxide is also used. Although its physical properties imply that anesthesia can be induced more rapidly than with halothane, its pungency can irritate the respiratory system, negating this theoretical advantage conferred by its physical properties. It is usually used to maintain a state of general anesthesia that has been induced with another drug, such as thiopentone or propofol.

Enflurane (2-chloro-1,1,2,-trifluoroethyl-difluoromethyl ether) is a halogenated ether structural isomer of isoflurane. Developed by Ross Terrell in 1963, it was first used clinically in 1966. It was increasingly used for inhalational anesthesia during the 1970s and 1980s but is no longer in common use. Clinically, enflurane produces a dose-related depression of myocardial contractility with an associated decrease in myocardial oxygen consumption. Between 2% and 5% of the inhaled dose is oxidized in the liver, producing fluoride ions and difluoromethoxy-difluoroacetic acid. This is significantly higher than the metabolism of its structural isomer isoflurane. The exact mechanism of the action of general anesthetics has not been delineated. Enflurane acts as a positive allosteric modulator of the GABAA, glycine, and 5-HT3 receptors, and as a negative allosteric modulator of the AMPA, kainate, and NMDA receptors, as well as of nicotinic acetylcholine receptors.