Enflurane

Enflurane

Systematic (IUPAC) name
(RS)-2-chloro-1-(difluoromethoxy)-1,1,2-trifluoro-ethane
Clinical data
AHFS/Drugs.com	Micromedex Detailed Consumer Information
Pharmacokinetic data
Protein binding	97%
Identifiers
CAS Number	13838-16-9 Y
ATC code	N01AB04 (WHO)
PubChem	CID: 3226
IUPHAR/BPS	7175
DrugBank	DB00228 Y
ChemSpider	3113 Y
UNII	91I69L5AY5 Y
KEGG	D00543 Y
ChEBI	CHEBI:4792 Y
ChEMBL	CHEMBL1257 Y
Chemical data
Formula	C3H2ClF5O
Molecular mass	184.492 g/mol
SMILES FC(Cl)C(F)(F)OC(F)F
InChI InChI=1S/C3H2ClF5O/c4-1(5)3(8,9)10-2(6)7/h1-2H Y Key:JPGQOUSTVILISH-UHFFFAOYSA-N Y
(verify)

Enflurane (2-chloro-1,1,2,-trifluoroethyl-difluoromethyl ether) is a halogenated ether. 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.

Enflurane is a structural isomer of isoflurane. It vaporizes readily, but is a liquid at room temperature.

Physical properties

Property	Value
Boiling point at 1 atm	56.5 °C
MAC	1.68
Vapor pressure at 20 °C	22.9 kPa (172 mm Hg)
Blood:gas partition coefficient	1.9
Oil:gas partition coefficient	98

Side effects

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 oxidised in the liver, producing fluoride ions and difluoromethoxy-difluoroacetic acid. This is significantly higher than the metabolism of its structural isomer isoflurane.

Enflurane also lowers the threshold for seizures, and should especially not be used on people with epilepsy. It is also known to cause malignant hyperthermia.

It relaxes the uterus in pregnant women.

Enflurane and methoxyflurane have a nephrotoxic effect and cause acute renal failure, usually by its nephrotoxic metabolite.

Pharmacology

The exact mechanism of the action of general anaesthetics have not been delineated. Enflurane acts as a positive allosteric modulator of the GABA_A, 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.

Occupational safety

In the workplace, people may be exposed to enflurane by breathing it in as a waste anaesthetic gas, swallowing it, eye contact, or skin contact. The National Institute for Occupational Safety and Health (NIOSH) has set a recommended exposure limit (REL) for exposure to waste anaesthetic gas of 2 ppm (15.1 mg/m³) over a 60 minute period. Symptoms of occupational exposure to enflurane include eye irritation, central nervous system depression, analgesia, anesthesia, convulsions, and respiratory depression.