Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
ETHRANE vs FLUOTHANE
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Enflurane is a volatile inhalational anesthetic that potentiates GABA-A receptor activity and inhibits excitatory neurotransmission, resulting in general anesthesia.
Halothane enhances GABA-A receptor activity and inhibits NMDA receptors, leading to neuronal hyperpolarization and decreased excitability. It also potentiates glycine receptor function and disrupts synaptic transmission via interaction with voltage-gated sodium channels.
Induction and maintenance of general anesthesia
Induction and maintenance of general anesthesia,Off-label: Use for status asthmaticus (rarely)
1-5% inspired concentration via inhalation, titrated to effect for maintenance of general anesthesia.
Induction: 0.5-3% halothane in oxygen or nitrous oxide/oxygen; maintenance: 0.5-1.5%.
Context-sensitive half-life: approximately 2-5 minutes after short procedures; prolonged after prolonged administration due to slow washout from fat stores.
Terminal elimination half-life is biphasic: initial 2-5 minutes (rapid redistribution), terminal 15-20 hours for trace amounts in adipose tissue due to slow release; contextually, emergence from anesthesia occurs within minutes.
Primarily hepatic via cytochrome P450 (CYP2E1); minor metabolism to fluoride ions.
Hepatic metabolism via cytochrome P450 enzymes (CYP2E1 major, CYP2A6 minor) to trifluoroacetic acid, chloride, and bromide ions; reductive metabolism under hypoxic conditions produces potentially hepatotoxic intermediates.
Primarily exhaled unchanged via lungs (>95%); less than 5% metabolized in liver to fluoride ion and other metabolites, with renal excretion of metabolites.
Primarily exhaled unchanged via the lungs; negligible renal (0.5% as metabolites) and fecal elimination.
Approximately 30-40%, primarily to albumin.
~40-50% bound to albumin.
Vd: 1.2-2.0 L/kg, indicating extensive distribution into tissues, especially fat.
2-5 L/kg; indicates extensive tissue distribution, particularly in adipose and brain.
By inhalation: 100% as delivered; not administered orally.
Inhalation: 100% (administered as gas); no other relevant routes.
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.
No dose adjustment required for renal impairment; halothane is minimally excreted renally.
No specific Child-Pugh based adjustment; use with caution in severe hepatic impairment as metabolism may be decreased.
Contraindicated in patients with Child-Pugh class B or C cirrhosis due to risk of hepatotoxicity; use with caution in mild impairment with reduced doses.
Induction: 2-5% inspired concentration; Maintenance: 1-3% inspired concentration, adjusted to age and response.
Induction: 0.5-2% halothane in oxygen; maintenance: 0.3-1%. Dose based on response.
Lower inspired concentrations (0.5-2%) recommended due to increased sensitivity and reduced clearance; titrate to effect.
Reduce induction concentration to 0.5-1% and maintenance to 0.5% due to increased sensitivity and slower clearance.
None
Halothane is associated with a risk of life-threatening hepatic injury, including fatal hepatic necrosis, primarily following repeated exposure or in patients with known hypersensitivity. It should be avoided in patients with a history of unexplained jaundice or fever after halothane administration.
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
Risk of hepatic necrosis (especially with repeated use); malignant hyperthermia; respiratory depression; hypotension; cardiac arrhythmias (including sensitization to catecholamines); increased intracranial pressure; requires trained personnel and monitoring; use caution in patients with hepatic disease.
Known hypersensitivity to enflurane or other halogenated anesthetics,Known or suspected susceptibility to malignant hyperthermia,Severe hepatic impairment,Uncontrolled epilepsy
Known hypersensitivity to halothane or other halogenated anesthetics; history of unexplained jaundice or fever after halothane administration; suspected or known hepatic injury from halogenated anesthetics; risk of malignant hyperthermia (including family history).
No specific food interactions. Patient must follow preoperative fasting guidelines (nil per os, NPO) as directed by anesthesiologist to reduce risk of aspiration.
No specific food interactions known, but fasting is required preoperatively to prevent aspiration pneumonitis caused by relaxation of the lower esophageal sphincter and loss of airway reflexes.
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.
FDA Pregnancy Category C. First trimester: Increased risk of congenital anomalies (cleft palate, skeletal defects) in animal studies; avoid unless essential. Second and third trimesters: Prolonged exposure may cause neonatal respiratory depression, hypotonia, and thermoregulatory instability; risk of fetal hypoxia due to maternal hypotension.
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.
Halothane is excreted in breast milk in low concentrations. M/P ratio not determined. Short-term use is considered compatible with breastfeeding; avoid prolonged or repeated exposure. Monitor infant for sedation and feeding difficulties.
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.
Increased sensitivity to myocardial depression; reduce dose by 25-50% in pregnant patients. Monitor closely for hypotension. No specific pharmacokinetic adjustments required due to pregnancy, but consider decreased MAC (minimum alveolar concentration) in late pregnancy.
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.
Halothane is a potent inhalational anesthetic with low blood-gas solubility, allowing rapid induction and emergence. It sensitizes the myocardium to catecholamines, increasing risk of arrhythmias, especially with epinephrine use. Halothane can cause hepatic necrosis, particularly with repeated exposure (halothane hepatitis). Avoid in patients with unexplained jaundice after prior halothane use. Use low concentrations with spontaneous ventilation to prevent respiratory depression.
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.
Avoid food or drink for at least 6-8 hours before surgery to reduce aspiration risk.,Report any history of liver disease or allergic reactions to anesthesia.,You may experience shivering or nausea after waking up from anesthesia.,Do not drive or operate machinery for at least 24 hours after anesthesia.,Inform your doctor if you notice yellowing of skin or eyes, dark urine, or severe fatigue after surgery.
No interactions on record
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about ETHRANE vs FLUOTHANE, answered by our medical review team.
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.. FLUOTHANE is a General Anesthetic that works by Halothane enhances GABA-A receptor activity and inhibits NMDA receptors, leading to neuronal hyperpolarization and decreased excitability. It also potentiates glycine receptor function and disrupts synaptic transmission via interaction with voltage-gated sodium channels.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between ETHRANE and FLUOTHANE 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 ETHRANE is: 1-5% inspired concentration via inhalation, titrated to effect for maintenance of general anesthesia.. The standard adult dose of FLUOTHANE is: Induction: 0.5-3% halothane in oxygen or nitrous oxide/oxygen; maintenance: 0.5-1.5%.. 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 ETHRANE and FLUOTHANE 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. 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 . FLUOTHANE is classified as Category C. FDA Pregnancy Category C. First trimester: Increased risk of congenital anomalies (cleft palate, skeletal defects) in animal studies; avoid unless essential. Second and third trime. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.