Inhalational anesthetics

Last updated: April 26, 2022

Summarytoggle arrow icon

Inhalational anesthetics are used for the induction and maintenance of general anesthesia as well as sedation. The exact mechanisms by which they act are still unknown. The most common inhalational anesthetics are sevoflurane, desflurane, and nitrous oxide. Of these, sevoflurane is the most common because of its rapid onset of action and the fact that patients recover quickly from it. Inhalational anesthetics cause respiratory depression, a decrease in arterial blood pressure and cerebral metabolic demand, and an increase in cerebral blood flow. While side effects differ based on the substance (e.g., halothane can cause hepatotoxicity), the most common side effect is nausea.

Overviewtoggle arrow icon

Overview of inhalational anesthetics
Agents Indications Mechanism of action Adverse effects
Nitrous oxide
  • Exact mechanism of action still unknown, leads to:
    • Sedation/narcosis
    • Anesthesia (nitrous oxide)
    • ↓ Respiration and arterial blood pressure, myocardial depression
    • ↑ Cerebral blood flow and ICP, ↓ cerebral metabolic demand
  • Can diffuse into gas-filled body compartments → expansion of the gas in that compartment
  • ↑ Pulmonary vessel resistance
  • Agitation (especially in pediatric patients) [1]
  • Proconvulsive

Pharmacokinetics and pharmacodynamicstoggle arrow icon

Pharmacokinetic principles

Pharmacodynamic principles

Pharmacokinetics and pharmacodynamics of common inhalational anesthetics


Pharmacodynamicstoggle arrow icon

General effects

  • Anesthesia
  • Sedation/narcosis
  • ↓ Respiration
  • ↓ Arterial blood pressure
  • Myocardial depression
  • ↓ Cerebral metabolic demand
  • ↑ Cerebral blood flow
  • ↑ ICP
  • Postoperative: nausea and vomiting

Specific characteristics of common inhalational anesthetics

Specific characteristics
Nitrous oxide
  • Can cause expansion of gas trapped in a cavity
  • Usually insufficient if used alone → often combined with a more potent inhalational anesthetic to achieve the “second gas effect”
  • Rapid onset and recovery
  • Very rapid onset and recovery
  • Pungent odor; irritates airways → not suitable for induction of anesthesia
  • Most commonly used inhalational anesthetic
  • Rapid onset and recovery
  • Nonpungent → suitable for induction of anesthesia
  • Most potent of the fluranes
  • Relatively slow onset and recovery
  • Pungent odor → not suitable for induction of anesthesia
  • Seizures (proconvulsive)
  • Medium speed of onset and recovery


Adverse effectstoggle arrow icon

General side effects

Side effects of specific substances


We list the most important adverse effects. The selection is not exhaustive.

Referencestoggle arrow icon

  1. $ULTANE® (sevoflurane) volatile liquid for inhalation.
  2. $FORANE (isoflurane, USP) Liquid For Inhalation.
  3. Le T, Bhushan V. First Aid for the USMLE Step 1 2015. McGraw-Hill Education ; 2014
  4. Katzung B,Trevor A. Basic and Clinical Pharmacology. McGraw-Hill Education ; 2014
  5. King A, Weavind LM, Joshi GP, Nussmeier NA. General Anesthesia: Induction. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. Last updated: September 7, 2017. Accessed: September 25, 2017.
  6. ASA. Practice guidelines for preoperative fasting and the use of pharmacologic agents to reduce the risk of pulmonary aspiration: Application to healthy patients undergoing elective procedures. Anesthesiology. 2011; 114 (3): p.495-511.doi: 10.1097/aln.0b013e3181fcbfd9 . | Open in Read by QxMD
  7. Drug record - Halothane. . Accessed: October 6, 2017.
  8. Halothane Hepatotoxicity. Updated: October 17, 2016. Accessed: October 12, 2017.
  9. Eger EI II . Characteristics of anesthetic agents used for induction and maintenance of general anesthesia. Am J Health Syst Pharm. 2004; 61 (20).
  10. Wenker OC. Review of Currently Used Inhalation Anesthetics; Part I. The Internet Journal of Anesthesiology. 1999; 2 (3).

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