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Halogenated ether

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Structural formula of isoflurane, a typical halogenated ether. The C—O—C (carbon-oxygen-carbon) in the center is the ether group and the Cl (chlorine) and F (fluorine) are the halogen atoms, which have been substituted for all but two H (hydrogen) atoms.

Halogenated ethers are a subcategory of ethers—organic chemicals that containan oxygen atom connected to two alkyl groups or similar structures. An example of an ether is the solvent diethyl ether.[1]Halogenated ethers differ from other ethers because there are one or more halogen atoms—fluorine, chlorine, bromine, or iodine—as substituents on the carbon groups. .[2] Examples of commonly used halogenated ethers include halothane, isoflurane, sevofluorane and desflurane.[3]

History

An ideal inhaled anesthetic wasn't found until 1950. Volatile substances like diethyl ether, which have severe risks of nausea, were used before.[4] Diethyl ether has the unfortunate disadvantage of being extremely flammable, especially in the presence of enriched oxygen mixtures. Thus, there were many instances of fires and even explosions during surgery.[5]

James Young Simpson

James Young Simpson, an obstetrics surgeon, used ethers to help women relieve their labor pains but ultimately deemed them unsuitable due to their drawbacks. Simpson and his friends tested the halogenated hydrocarbon, chloroform, as a substitute inhalation agent during a house party. They woke from unconsciousness pleasantly surprised with the its effectiveness. This was the first recorded successful use of halogenated hydrocarbons as anesthetics. [4]

Common Halogenated Ethers

Common halogenated ethers with chemical structure and formula
Halogenated Ether Chemical Formula Chemical Structure Use
Sevoflurane C4H3F7O
Induction and maintenance of general anesthesia for adults and children. [6]
Isoflurane C3H2ClF5O
Induction and maintenance of general anesthesia for adults and children. [7]
Desflurane C3H2F6O Induction and maintenance of general anesthesia for adults. Maintenance in children following induction by other agents. [8]
Methoxyflurane C3H4Cl2F2O Short term pain relief; rarely used for chronic pain or as an anesthetic because of nephrotoxicity risks. [9]
Enflurane C3H2ClF5O Induction and maintenance of general anesthesia. Used to reduce pain during vaginal delivery. [10]

Use in anesthesiology

Perhaps the most common use of halogenated ethers has been in anesthesiology.[11] The first widely used inhalation anesthetic was diethyl ether, which is a non-substituted (non-halogenated) ether. This drug enabled surgeons to perform otherwise painful operations on patients after rendering them unconscious.[12]

Diethyl ether has the unfortunate disadvantage of being extremely flammable, especially in the presence of enriched oxygen mixtures.[13] This property has resulted in many instances of fires and even explosions in operating rooms during surgery. Thus, diethyl ether has fallen out of favor as a general anesthetic.[14]

Diethyl ether was initially replaced by non-flammable (but more toxic) halogenated hydrocarbons such as chloroform and trichloroethylene. Halothane is another halogenated hydrocarbon anesthetic agent which was introduced into clinical practice in 1956. Due to its ease of use and improved safety profile with respect to organ toxicity, halothane quickly replaced chloroform and trichloroethylene.

All inhalation anesthetics in current clinical use are halogenated ethers, except for halothane (which is a halogenated hydrocarbon or haloalkane), nitrous oxide, and xenon.[15]

Halogenated ethers have the advantages of being non-flammable as well as less toxic than earlier general anesthetics. Halogenated ethers differ from other ethers because they contain at least one halogen atom in each molecule. Examples of halogenated ethers include the general anesthetics isoflurane, desflurane, and sevoflurane. However, not all halogenated ethers have anesthetic effects, and some compounds such as flurothyl do the opposite and have stimulant and convulsant effects.

Inhalation anesthetics are vaporized and mixed with other gases prior to their inhalation by the patient before or during surgery. These other gases always include oxygen or air, but may also include other gases such as nitrous oxide or helium. In most surgical situations, other drugs such as opiates are used for pain and skeletal muscle relaxants are used to cause temporary paralysis. Additional drugs such as midazolam may be used to produce amnesia during surgery. Although newer intravenous anesthetics (such as propofol) have increased the options of anesthesiologists, halogenated ethers remain a mainstay of general anesthesia.

Use in polymers

The perfluorinated epoxides are used as comonomers for the production of polytetrafluoroethylene.[16]

See also

References

  1. ^ Schmitt, Laura; Hinxlage, Ilka; Cea, Pablo A.; Gohlke, Holger; Wesselborg, Sebastian (2021-02-13). "40 Years of Research on Polybrominated Diphenyl Ethers (PBDEs)—A Historical Overview and Newest Data of a Promising Anticancer Drug". Molecules. 26 (4): 995. doi:10.3390/molecules26040995. ISSN 1420-3049. PMC 7918430. PMID 33668501.
  2. ^ Tang, Shaokun; Baker, Gary A.; Zhao, Hua (2012). "Ether- and alcohol-functionalized task-specific ionic liquids: attractive properties and applications". Chemical Society Reviews. 41 (10): 4030–4066. doi:10.1039/c2cs15362a. ISSN 0306-0012. PMC 3341508. PMID 22456483.
  3. ^ Bertram-Ralph, Elliott; Amare, Muataz (2022-01-01). "Inhalational anaesthesia". Anaesthesia & Intensive Care Medicine. 23 (1): 60–68. doi:10.1016/j.mpaic.2021.10.003. ISSN 1472-0299.
  4. ^ a b Whalen, Francis X.; Bacon, Douglas R.; Smith, Hugh M. (2005-09-01). "Inhaled anesthetics: an historical overview". Best Practice & Research Clinical Anaesthesiology. Renaissance of Inhalational Anaesthesia. 19 (3): 323–330. doi:10.1016/j.bpa.2005.02.001. ISSN 1521-6896.
  5. ^ insideout (2015-04-27). "Understanding the Safety Risks of Diethyl Ether". VelocityEHS. Retrieved 2024-11-04.
  6. ^ "Sevoflurane (inhalation route)". Mayo Clinic. Retrieved 2024-12-01.
  7. ^ "Isoflurane (inhalation route)". Mayo Clinic. Retrieved 2024-12-01.
  8. ^ Khan, Joohi; Patel, Preeti; Liu, Mark (2024), "Desflurane", StatPearls, Treasure Island (FL): StatPearls Publishing, PMID 30725791, retrieved 2024-12-01
  9. ^ Methoxyflurane Inhalation as an Analgesic for Minor Gynecological, Ambulatory, or Emergency Procedures: Rapid Review. CADTH Health Technology Review. Ottawa (ON): Canadian Agency for Drugs and Technologies in Health. 2024. PMID 39466939.
  10. ^ PubChem. "Enflurane". pubchem.ncbi.nlm.nih.gov. Retrieved 2024-12-01.
  11. ^ "Halogenated Anesthetics", LiverTox: Clinical and Research Information on Drug-Induced Liver Injury, Bethesda (MD): National Institute of Diabetes and Digestive and Kidney Diseases, 2012, PMID 31644158, archived from the original on 2022-08-21, retrieved 2022-08-21
  12. ^ Dunstan M (October 22, 2016). "Ether: The First Anaesthetic – Scientific Scribbles". The University of Melbourne. Retrieved 2022-08-21.
  13. ^ "Diethyl Ether". webwiser.nlm.nih.gov. National Library of Medicine. Retrieved 2022-08-21.
  14. ^ Macdonald AG (December 1994). "A brief historical review of non-anaesthetic causes of fires and explosions in the operating room". British Journal of Anaesthesia. 73 (6): 847–856. doi:10.1093/bja/73.6.847. PMID 7880680.
  15. ^ Luethy A, Boghosian JD, Srikantha R, Cotten JF (June 2017). "Halogenated Ether, Alcohol, and Alkane Anesthetics Activate TASK-3 Tandem Pore Potassium Channels Likely through a Common Mechanism". Molecular Pharmacology. 91 (6): 620–629. doi:10.1124/mol.117.108290. PMC 5438130. PMID 28325748.
  16. ^ Siegemund, Günter; Schwertfeger, Werner; Feiring, Andrew; Smart, Bruce; Behr, Fred; Vogel, Herward; McKusick, Blaine; Kirsch, Peer (2016-01-28). "Fluorine Compounds, Organic". Ullmann's Encyclopedia of Chemical Technology. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA. pp. 1–56. doi:10.1002/14356007.a11_349.pub2. ISBN 978-3-527-30673-2.
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