|Trade names||Forane, others|
|AHFS/Drugs.com||FDA Professional Drug Information|
|Chemical and physical data|
|Molar mass||184.5 g/mol|
|3D model (JSmol)|
Isoflurane, sold under the trade name Forane among others, is a general anesthetic. It can be used to start or maintain anesthesia. Often another medication is used to start anesthesia due to airway irritation with isoflurane. It is used by inhalation.
Side effects include a decreased ability to breathe (respiratory depression), low blood pressure, and irregular heartbeat. Serious side effects may include malignant hyperthermia and high blood potassium. It should not be used in people with a history of malignant hyperthermia in either themselves or their family members. It is unknown if use during pregnancy is safe for the baby, but use during a cesarean section appears to be safe. Isoflurane is in the halogenated ether family of medication.
Isoflurane was approved for medical use in the United States in 1979. It is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system. The wholesale cost in the developing world is about 17.24 to 170.40 USD per 250 ml bottle.
Isoflurane is always administered in conjunction with air and/or pure oxygen. Often nitrous oxide is also used. Although its physical properties imply that anaesthesia can be induced more rapidly than with halothane, its pungency can irritate the respiratory system, negating any possible advantage conferred by its physical properties. It is usually used to maintain a state of general anesthesia which has been induced with another drug, such as thiopentone or propofol.
Animal studies have raised safety concerns of certain general anesthetics, in particular ketamine and isoflurane, in young children. The risk of neurodegeneration was increased in combination of these agents with nitrous oxide and benzodiazepines such as midazolam. Whether these concerns occur in humans is unclear.
Concerns exist with regard to the relationship between administration of isoflurane and postoperative cognitive dysfunction (POCD), for which the elderly are especially vulnerable.
Biophysical studies using NMR spectroscopy has provided molecular details of how inhaled anesthetics interact with three amino acid residues (G29, A30 and I31) of amyloid beta peptide and induce aggregation. This area is important as "some of the commonly used inhaled anesthetics may cause brain damage that accelerates the onset of Alzheimer’s disease".
|Boiling point (at 1 atm):||48.5 °C|
|Density (at 25 °C):||1.496 g/mL|
|MAC :||1.15 vol %|
|Vapor pressure:||238 mmHg||31.7 kPa||(at 20 °C)|
|295 mmHg||39.3 kPa||(at 25 °C)|
|367 mmHg||48.9 kPa||(at 30 °C)|
|450 mmHg||60.0 kPa||(at 35 °C)|
|Water solubility||13.5 mM||(at 25 °C)|
|Blood:gas partition coefficient:||1.4|
|Oil:gas partition coefficient:||98|
Mechanism of action
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 binds to GABA, glutamate and glycine receptors, but has different effects on each receptor. Isoflurane acts as a positive allosteric modulator of the GABAA receptor in electrophysiology studies of neurons and recombinant receptors. It potentiates glycine receptor activity, which decreases motor function. It inhibits receptor activity in the NMDA glutamate receptor subtypes. Isoflurane inhibits conduction in activated potassium channels. Isoflurane also affects intracellular molecules. It activates calcium ATPase by increasing membrane fluidity . It binds to the D subunit of ATP synthase and NADH dehydrogenase.
Together with enflurane and halothane, it replaced the flammable ethers used in the pioneer days of surgery. Its name comes from being a structural isomer of enflurane, hence they have the same empirical formula.
The average lifetime of isoflurane in the atmosphere is 3.2 years, its global warming potential is 510 and the yearly emissions add up to 880 tons.
Isoflurane is frequently used for veterinary anaesthesia.
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