Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
ISOFLURANE vs ULTANE
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Isoflurane is a general inhalation anesthetic that acts as a positive allosteric modulator of GABA-A receptors and glycine receptors, and inhibits excitatory receptors such as NMDA and AMPA receptors. It potentiates inhibitory neurotransmission and depresses excitatory neurotransmission, leading to anesthesia, amnesia, and muscle relaxation.
Sevoflurane is a volatile general anesthetic that enhances inhibitory neurotransmission via GABA-A and glycine receptors, and inhibits excitatory neurotransmission via NMDA and nicotinic acetylcholine receptors, producing anesthesia, amnesia, and muscle relaxation.
Induction and maintenance of general anesthesia,Sedation in mechanically ventilated patients (off-label)
Induction and maintenance of general anesthesia in adult and pediatric patients for inpatient and outpatient surgery
Induction: 1-3% in oxygen or oxygen/nitrous oxide mixture via inhalation; Maintenance: 0.5-2% in oxygen or oxygen/nitrous oxide mixture via inhalation.
Inhalation: Induction, 0.5-3% sevoflurane in oxygen or oxygen/nitrous oxide; maintenance, 1.5-3% sevoflurane with or without nitrous oxide.
Terminal elimination half-life is approximately 2.5 to 5 hours. Context: The context-sensitive half-time varies with duration of anesthesia; for short procedures (<1 hour), half-life is about 2-4 minutes, but for prolonged anesthesia, it can be 30-60 minutes due to redistribution from fat stores.
Terminal elimination half-life of inorganic fluoride is approximately 2-5 hours (mean 3.0 h) in adults; context: prolonged with obesity or renal impairment.
Isoflurane undergoes minimal metabolism (approximately 0.2%) primarily via hepatic cytochrome P450 enzymes (CYP2E1), leading to the production of inorganic fluoride and trifluoroacetic acid. The major route of elimination is via exhalation as unchanged drug.
Approximately 5% of sevoflurane is metabolized by cytochrome P450 (CYP2E1) to hexafluoroisopropanol (HFIP), carbon dioxide, and inorganic fluoride.
Primarily eliminated via exhalation through the lungs (>99%). Less than 1% undergoes hepatic metabolism to trifluoroacetic acid and fluoride ions, which are excreted renally.
Renal excretion of inorganic fluoride metabolites accounts for >95% of elimination; <5% excreted unchanged in urine.
Approximately 5-20% bound to plasma proteins, primarily albumin.
Minimal binding to plasma proteins; <5% bound.
Volume of distribution is about 2-5 L/kg, reflecting extensive tissue distribution, especially to lipid-rich tissues like brain and fat.
Volume of distribution at steady state: 0.5-1.5 L/kg (mean 1.0 L/kg); large Vd indicates extensive tissue distribution.
Inhalation: Bioavailability is essentially 100% for inspired drug; systemic absorption is nearly complete due to rapid pulmonary exchange.
Inhalation: ~100% bioavailable; no oral route.
No dose adjustment required in renal impairment; pharmacokinetics unaffected.
No dose adjustment required for GFR ≥30 m L/min; use with caution in GFR <30 m L/min due to potential for elevated fluoride concentrations, but no specific dose adjustment recommended.
No specific dose adjustment guidelines; use with caution in severe hepatic impairment due to potential for hepatotoxicity.
No dose adjustment required for Child-Pugh A or B; use with caution in Child-Pugh C, but no specific dose adjustment recommended.
Induction: 1.5-3% in oxygen or oxygen/nitrous oxide mixture; Maintenance: 0.5-2% in oxygen or oxygen/nitrous oxide mixture; titrate to effect.
Induction: 2-4% sevoflurane in oxygen or oxygen/nitrous oxide, up to 8% for mask induction; maintenance: 1.5-3% with or without nitrous oxide.
Reduce concentrations by 20-50% due to increased sensitivity and decreased MAC; monitor hemodynamics closely.
Elderly patients are more sensitive to sevoflurane; use lower doses for induction and maintenance, typical maintenance 0.5-2% sevoflurane.
Because isoflurane is a potent halogenated anesthetic, it may cause malignant hyperthermia, a life-threatening condition characterized by hypermetabolism, muscle rigidity, tachycardia, and hyperthermia. Immediate treatment with dantrolene and discontinuation of triggering agents is essential.
None
Risk of malignant hyperthermia,Respiratory depression,Hypotension and myocardial depression,Elevated intracranial pressure,Hepatic injury (rare),Nephrotoxicity due to fluoride ion (rare),QT interval prolongation,Use with caution in patients with coronary artery disease
Risk of malignant hyperthermia; may cause respiratory depression; caution in patients with preexisting respiratory or cardiovascular disease; monitor for hepatotoxicity; use with caution in patients with renal impairment (elevated fluoride levels); sevoflurane may cause QT prolongation
Known or suspected susceptibility to malignant hyperthermia,Prior history of unexplained jaundice or fever after isoflurane administration,Concurrent use of entacapone (increased risk of intraoperative myocardial depression)
Known or suspected susceptibility to malignant hyperthermia,Known sensitivity to sevoflurane or other halogenated agents
No specific food interactions with isoflurane. However, fasting before anesthesia is required to reduce the risk of pulmonary aspiration.
No specific food interactions with sevoflurane. However, patients should adhere to preoperative fasting guidelines (typically 6-8 hours for solids, 2 hours for clear liquids) to reduce aspiration risk during anesthesia.
Isoflurane is not associated with major congenital malformations but may cause fetal depression, especially during third trimester. Avoid elective use until after delivery.
Sevoflurane (ULTANE) is classified as FDA Pregnancy Category B. Animal studies have not demonstrated teratogenic or fetotoxic effects at clinically relevant doses. In humans, limited data do not indicate an increased risk of major malformations with first-trimester exposure. However, use during the second and third trimesters may cause transient neonatal depression, including hypotonia and respiratory depression, due to placental transfer. Prolonged or repeated exposure should be avoided, especially during organogenesis, as with all volatile anesthetics.
Minimal transfer into breast milk; M/P ratio unknown. Considered compatible with breastfeeding after single exposure; observe infant for sedation.
Sevoflurane is excreted into breast milk in low quantities. The milk-to-plasma (M/P) ratio has not been specifically determined for sevoflurane, but based on physicochemical properties, it is expected to be low. Due to rapid clearance and low oral bioavailability, the risk to a nursing infant is considered minimal after a single anesthetic dose. However, it is recommended to express and discard breast milk for 24 hours after anesthesia to minimize infant exposure.
No dose adjustment required for pregnancy per se; however, MAC decreases by about 25-40% during pregnancy due to hormonal changes and increased progesterone. Use lowest effective dose.
During pregnancy, pharmacokinetic changes such as increased plasma volume, decreased protein binding, and increased cardiac output may necessitate dose adjustments. Sevoflurane requirements may be reduced by approximately 25-30% during pregnancy due to increased sensitivity to volatile anesthetics and decreased minimum alveolar concentration (MAC). Induction and maintenance doses should be titrated to effect, with close hemodynamic monitoring to avoid hypotension. No specific dose reduction is mandated, but careful titration is recommended.
Isoflurane is a halogenated ether anesthetic. It causes dose-dependent hypotension primarily through vasodilation. It is not recommended for induction in pediatrics due to pungency and airway irritability. Malignant hyperthermia trigger. Use with caution in patients with elevated intracranial pressure as it can increase cerebral blood flow. Monitor end-tidal CO2 and volatile agent concentration.
ULTANE (sevoflurane) is a volatile anesthetic with low blood-gas solubility, facilitating rapid induction and emergence. It is associated with a risk of malignant hyperthermia; have dantrolene available. Sevoflurane can degrade in carbon dioxide absorbents to compound A, which may cause renal injury; use fresh gas flows ≥2 L/min to minimize this risk. Monitor end-tidal sevoflurane concentration closely, as hypotension and respiratory depression are dose-dependent.
You will receive isoflurane gas to keep you asleep and pain-free during surgery.,You may experience shivering or nausea after awakening; tell your nurse if severe.,Do not eat or drink for the time instructed before surgery to prevent aspiration.,If you have a personal or family history of malignant hyperthermia, inform your anesthesiologist immediately.,Arrange for a ride home after surgery as isoflurane can impair coordination and judgment for up to 24 hours.
You will receive this medication only under the supervision of an anesthesia professional,Do not eat or drink before surgery as instructed by your doctor,You may experience dizziness or drowsiness after waking; do not drive for 24 hours,Report any history of kidney disease or adverse reactions to anesthesia,Inform your doctor if you are pregnant or breastfeeding,You will be monitored throughout the procedure for vital signs and safety
"Telithromycin, a macrolide antibiotic, prolongs the QT interval by blocking the rapid component of the delayed rectifier potassium current (IKr). Isoflurane, a volatile anesthetic, also prolongs the QT interval via inhibition of IKr and other cardiac ion channels. The combination may lead to additive or synergistic QT prolongation, increasing the risk of torsades de pointes, a potentially fatal ventricular arrhythmia, especially in patients with other risk factors such as hypokalemia, bradycardia, or pre-existing cardiac disease."
"Isoflurane, a volatile halogenated anesthetic, potentiates the cardiodepressant and arrhythmogenic effects of levobupivacaine, a long-acting amide local anesthetic, by inhibiting myocardial calcium channels and β-adrenergic responsiveness. This additive negative inotropic and chronotropic effect increases the risk of hypotension, bradycardia, and potentially life-threatening ventricular arrhythmias during combined use. Additionally, isoflurane may delay levobupivacaine metabolism by reducing hepatic blood flow, prolonging systemic exposure and toxicity."
"The combination of isoflurane and thiamylal results in synergistic CNS depression and enhanced negative inotropic and vasodilatory effects on the cardiovascular system. Isoflurane potentiates the barbiturate-induced suppression of myocardial contractility and baroreceptor reflexes, leading to a heightened risk of hypotension, bradycardia, and reduced cardiac output. Clinically, patients may experience profound anesthesia, prolonged recovery, and hemodynamic instability, especially during induction and maintenance of anesthesia."
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about ISOFLURANE vs ULTANE, answered by our medical review team.
ISOFLURANE is a Inhalational Anesthetic that works by Isoflurane is a general inhalation anesthetic that acts as a positive allosteric modulator of GABA-A receptors and glycine receptors, and inhibits excitatory receptors such as NMDA and AMPA receptors. It potentiates inhibitory neurotransmission and depresses excitatory neurotransmission, leading to anesthesia, amnesia, and muscle relaxation.. ULTANE is a Inhalational Anesthetic that works by Sevoflurane is a volatile general anesthetic that enhances inhibitory neurotransmission via GABA-A and glycine receptors, and inhibits excitatory neurotransmission via NMDA and nicotinic acetylcholine receptors, producing anesthesia, amnesia, and muscle relaxation.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between ISOFLURANE and ULTANE depend on the specific clinical indication. These are both Inhalational 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 ISOFLURANE is: Induction: 1-3% in oxygen or oxygen/nitrous oxide mixture via inhalation; Maintenance: 0.5-2% in oxygen or oxygen/nitrous oxide mixture via inhalation.. The standard adult dose of ULTANE is: Inhalation: Induction, 0.5-3% sevoflurane in oxygen or oxygen/nitrous oxide; maintenance, 1.5-3% sevoflurane with or without nitrous oxide.. 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 ISOFLURANE and ULTANE 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. ISOFLURANE is classified as Category C. Isoflurane is not associated with major congenital malformations but may cause fetal depression, especially during third trimester. Avoid elective use until after delivery.. ULTANE is classified as Category C. Sevoflurane (ULTANE) is classified as FDA Pregnancy Category B. Animal studies have not demonstrated teratogenic or fetotoxic effects at clinically relevant doses. In humans, limit. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.