Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
HALOTHANE vs ETHRANE
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Halothane is a volatile halogenated hydrocarbon anesthetic that acts as a positive allosteric modulator of GABA-A receptors and glycine receptors, and inhibits NMDA and nicotinic acetylcholine receptors, leading to neuronal hyperpolarization and general anesthesia.
Enflurane is a volatile inhalational anesthetic that potentiates GABA-A receptor activity and inhibits excitatory neurotransmission, resulting in general anesthesia.
Induction and maintenance of general anesthesia,Sedation in intensive care (off-label),Status asthmaticus (off-label, due to bronchodilation)
Induction and maintenance of general anesthesia
Induction: 0.5-3% in oxygen or oxygen-nitrous oxide mixture, titrated to effect; Maintenance: 0.5-2% in oxygen or oxygen-nitrous oxide mixture.
1-5% inspired concentration via inhalation, titrated to effect for maintenance of general anesthesia.
Terminal elimination half-life approximately 5-10 hours post-anesthesia, with a slower terminal phase (up to 3 days) due to redistribution from fat stores. Clinically, washout is rapid initially but prolonged exposure in obese patients may lead to detectable levels for days.
Context-sensitive half-life: approximately 2-5 minutes after short procedures; prolonged after prolonged administration due to slow washout from fat stores.
Halothane is metabolized in the liver primarily by cytochrome P450 2E1 (CYP2E1) to trifluoroacetic acid and bromide ion; reductive metabolism also produces chloride ions and free radicals.
Primarily hepatic via cytochrome P450 (CYP2E1); minor metabolism to fluoride ions.
Primarily eliminated via pulmonary excretion (60-80% unchanged); approximately 20% metabolized in liver via CYP2E1, with metabolites excreted renally (trifluoroacetic acid, chloride, bromide). Only about 0.5% excreted unchanged in urine. Fecal excretion negligible.
Primarily exhaled unchanged via lungs (>95%); less than 5% metabolized in liver to fluoride ion and other metabolites, with renal excretion of metabolites.
Approximately 20-30% bound to plasma proteins, primarily albumin and lipoproteins.
Approximately 30-40%, primarily to albumin.
Volume of distribution at steady state (Vdss) approximately 2-5 L/kg; large Vd indicates extensive tissue distribution, especially to adipose tissue, brain, and muscle.
Vd: 1.2-2.0 L/kg, indicating extensive distribution into tissues, especially fat.
100% bioavailable via inhalation (only route of administration). Oral bioavailability not applicable.
By inhalation: 100% as delivered; not administered orally.
No specific dose adjustment required for renal impairment; use with caution due to potential nephrotoxicity from fluoride ions.
No dose adjustment required for GFR >10 m L/min; use with caution in severe renal impairment (GFR <10 m L/min) due to potential accumulation of inorganic fluoride metabolites.
Child-Pugh Class A: no adjustment; Child-Pugh Class B and C: avoid use; contraindicated in patients with hepatic impairment or history of halothane-induced hepatotoxicity.
No specific Child-Pugh based adjustment; use with caution in severe hepatic impairment as metabolism may be decreased.
Induction: 0.5-2% in oxygen or oxygen-nitrous oxide mixture, gradually increased; Maintenance: 0.3-1.5% as needed. Use lowest effective dose.
Induction: 2-5% inspired concentration; Maintenance: 1-3% inspired concentration, adjusted to age and response.
Reduce dose by 25-50% due to increased sensitivity and reduced clearance; monitor hemodynamics closely.
Lower inspired concentrations (0.5-2%) recommended due to increased sensitivity and reduced clearance; titrate to effect.
Halothane can cause hepatic necrosis, which may be fatal. Fatalities have occurred in patients with previous halothane exposure. Avoid repeat exposure within 3-6 months.
None
Hepatotoxicity (halothane hepatitis), malignant hyperthermia, cardiac arrhythmias (sensitizes myocardium to catecholamines), respiratory depression, hypotension, increased intracranial pressure.
May cause dose-dependent cardiovascular depression,Risk of malignant hyperthermia,Potential for nephrotoxicity due to fluoride release,Hepatotoxicity risk, especially with repeated use,Neurologic effects including seizure activity at high doses
Hypersensitivity to halothane, known or suspected susceptibility to malignant hyperthermia, history of unexplained jaundice or fever after halothane, hepatic dysfunction following previous halothane exposure, pregnancy (relative, especially first trimester).
Known hypersensitivity to enflurane or other halogenated anesthetics,Known or suspected susceptibility to malignant hyperthermia,Severe hepatic impairment,Uncontrolled epilepsy
No specific food interactions. However, fasting is required before anesthesia to reduce aspiration risk. Alcohol should be avoided for at least 24 hours post-anesthesia due to additive CNS depression.
No specific food interactions. Patient must follow preoperative fasting guidelines (nil per os, NPO) as directed by anesthesiologist to reduce risk of aspiration.
Halothane is classified as FDA Pregnancy Category C. Animal studies have shown teratogenic effects, but adequate human studies are lacking. First trimester exposure is associated with a potential increased risk of congenital malformations based on limited epidemiological data. Second and third trimester use may cause fetal depression and uterine atony; prolonged exposure can lead to neonatal respiratory depression. Avoid use during pregnancy unless clearly needed.
FDA Category B. No evidence of teratogenicity in animal studies; human data limited. Use only if clearly needed during pregnancy, especially first trimester due to potential fetal hypoxia from maternal hypotension.
Halothane is excreted into breast milk in small amounts. The milk-to-plasma (M/P) ratio is approximately 0.4. Due to low oral bioavailability, risks to the nursing infant are minimal. However, caution is advised as effects on the infant have not been fully studied. Consider pumping and discarding milk for 24-48 hours after anesthesia to minimize exposure.
Excreted in breast milk in low amounts; M/P ratio not established. Consider benefits of breastfeeding vs. risk of infant exposure. Minimal systemic absorption in infant expected.
No specific dose adjustment is recommended, but pregnancy alters pharmacokinetics: increased volume of distribution and decreased protein binding may require higher initial doses to achieve desired anesthetic depth. However, due to increased sensitivity to myocardial depression and uterine relaxation, use the minimum effective dose. Reduce concentration as needed to maintain uterine perfusion and avoid fetal hypoxia.
No specific dose adjustments required for pregnancy; however, MAC decreases by approximately 30% during pregnancy due to hormonal changes and increased progesterone. Monitor depth of anesthesia closely.
Halothane is a volatile halogenated hydrocarbon anesthetic. It sensitizes the myocardium to catecholamines, increasing risk of arrhythmias; avoid epinephrine use. Associated with halothane hepatitis (immune-mediated hepatotoxicity), especially with multiple exposures. Malignant hyperthermia trigger; have dantrolene ready. Use with caution in patients with increased intracranial pressure as it can elevate ICP. Use with low fresh gas flows to minimize pollution and cost.
ETHRANE (enflurane) is a potent inhalation anesthetic. Its use is limited due to risk of seizures at high doses and potential for nephrotoxicity from fluoride ion release. Avoid in patients with history of seizures or renal impairment. Rapid induction and recovery; use with caution in hypotensive patients due to myocardial depression. Malignant hyperthermia trigger.
This medication will make you unconscious for surgery. You will not feel pain or remember the procedure.,You must fast before anesthesia; do not eat or drink for at least 6-8 hours before surgery.,Tell your anesthesiologist about any liver problems or previous reactions to anesthesia.,Notify your doctor if you have a personal or family history of malignant hyperthermia.,Avoid alcohol for at least 24 hours after anesthesia.,Do not drive or operate machinery for 24 hours after receiving halothane.
You will receive this anesthesia medication only in a hospital setting under expert supervision.,Possible side effects include nausea, vomiting, shivering, and confusion after waking up.,Tell your doctor if you have a history of seizures, kidney problems, or muscle disorders.,Avoid driving or operating machinery for at least 24 hours after anesthesia.,Do not eat or drink for the time specified by your healthcare team before surgery.
"Efonidipine, a dihydropyridine calcium channel blocker, inhibits L-type and T-type calcium channels, leading to vasodilation and reduced myocardial contractility. Halothane, a volatile inhalational anesthetic, depresses myocardial function and sensitizes the myocardium to catecholamines, increasing the risk of arrhythmias. Concurrent use can result in additive negative inotropic effects and profound hypotension, potentially leading to cardiovascular collapse."
"Halothane, a volatile anesthetic, can inhibit the cytochrome P450 enzyme CYP2B6, which is primarily responsible for the metabolism of bupropion, an antidepressant and smoking cessation aid. This inhibition leads to decreased clearance of bupropion, resulting in elevated plasma concentrations that increase the risk of dose-dependent adverse effects such as seizures, anxiety, and insomnia. Clinically, patients may exhibit heightened neuropsychiatric toxicity and reduced seizure threshold, particularly during and after halothane anesthesia."
"Halothane, a volatile halogenated anesthetic, inhibits cytochrome P450 (CYP) isoenzymes, particularly CYP2C19, which is crucial for the hepatic bioactivation of clopidogrel to its active metabolite. Concomitant administration can lead to reduced plasma concentrations of the active thiol metabolite of clopidogrel, diminishing its antiplatelet effect and increasing the risk of thrombotic events such as stent thrombosis or myocardial infarction in patients with coronary artery disease. This interaction is especially significant in patients undergoing surgery where halothane is used for anesthesia while clopidogrel is indicated for recent acute coronary syndrome or percutaneous coronary intervention."
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about HALOTHANE vs ETHRANE, answered by our medical review team.
HALOTHANE is a General Anesthetic that works by Halothane is a volatile halogenated hydrocarbon anesthetic that acts as a positive allosteric modulator of GABA-A receptors and glycine receptors, and inhibits NMDA and nicotinic acetylcholine receptors, leading to neuronal hyperpolarization and general anesthesia.. ETHRANE is a General Anesthetic that works by Enflurane is a volatile inhalational anesthetic that potentiates GABA-A receptor activity and inhibits excitatory neurotransmission, resulting in general anesthesia.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between HALOTHANE and ETHRANE depend on the specific clinical indication. These are both General Anesthetic agents and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of HALOTHANE is: Induction: 0.5-3% in oxygen or oxygen-nitrous oxide mixture, titrated to effect; Maintenance: 0.5-2% in oxygen or oxygen-nitrous oxide mixture.. The standard adult dose of ETHRANE is: 1-5% inspired concentration via inhalation, titrated to effect for maintenance of general anesthesia.. Dosing should always be individualized based on indication, renal and hepatic function, age, and other patient factors.
No direct drug-drug interaction has been formally documented between HALOTHANE and ETHRANE in current clinical databases. However, individual patient risk factors including other medications, organ function, and comorbidities should always be evaluated by a qualified healthcare provider.
The maternal-fetal safety profiles differ. HALOTHANE is classified as Category C. Halothane is classified as FDA Pregnancy Category C. Animal studies have shown teratogenic effects, but adequate human studies are lacking. First trimester exposure is associated w. ETHRANE is classified as Category C. FDA Category B. No evidence of teratogenicity in animal studies; human data limited. Use only if clearly needed during pregnancy, especially first trimester due to potential fetal . Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.