Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
KETALAR vs FLUOTHANE
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Noncompetitive NMDA receptor antagonist; inhibits glutamate activity, modulates opioid receptors, and interacts with other neurotransmitter systems.
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,Procedural sedation and analgesia,Treatment of refractory status epilepticus (off-label),Major depressive disorder with suicidal ideation (off-label)
Induction and maintenance of general anesthesia,Off-label: Use for status asthmaticus (rarely)
1-4.5 mg/kg IV or 6.5-13 mg/kg IM for induction of anesthesia; 0.1-0.5 mg/kg/min IV infusion for maintenance.
Induction: 0.5-3% halothane in oxygen or nitrous oxide/oxygen; maintenance: 0.5-1.5%.
Terminal elimination half-life: 2.5-3 hours (ketamine); norketamine: 12 hours. Clinical context: Short half-life facilitates rapid recovery, but context-sensitive half-life increases with infusion duration.
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 N-demethylation by CYP3A4 and CYP2B6 to norketamine, then further metabolized via hydroxylation and conjugation.
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.
Renal: 90% as metabolites (norketamine, dehydronorketamine); unchanged: 2-4%. Fecal: <3%.
Primarily exhaled unchanged via the lungs; negligible renal (0.5% as metabolites) and fecal elimination.
12-50% primarily to albumin and alpha-1-acid glycoprotein.
~40-50% bound to albumin.
1-2 L/kg (large, indicating extensive tissue distribution). Highly lipophilic, crosses blood-brain barrier rapidly.
2-5 L/kg; indicates extensive tissue distribution, particularly in adipose and brain.
Oral: 16-24% (extensive first-pass metabolism); Intranasal: 45-50%; IM: 93%; Subcutaneous: 100%.
Inhalation: 100% (administered as gas); no other relevant routes.
No dose adjustment required for GFR >10 m L/min; for GFR <10 m L/min, consider dose reduction by 50% due to accumulation of active metabolite norketamine.
No dose adjustment required for renal impairment; halothane is minimally excreted renally.
Child-Pugh Class A: no adjustment; Child-Pugh Class B: reduce dose by 50%; Child-Pugh Class C: avoid use or use with extreme caution, reduce dose by 75%.
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: 1-2 mg/kg IV or 4-6 mg/kg IM; maintenance: 0.5-1 mg/kg IV boluses or 10-50 mcg/kg/min IV infusion. Titrate to effect.
Induction: 0.5-2% halothane in oxygen; maintenance: 0.3-1%. Dose based on response.
Reduce initial dose by 50% (e.g., 0.5-2 mg/kg IV) and titrate slowly due to increased sensitivity and risk of delirium; consider lower infusion rates (0.1-0.3 mg/kg/min).
Reduce induction concentration to 0.5-1% and maintenance to 0.5% due to increased sensitivity and slower clearance.
Hemodynamic instability (hypertension, tachycardia) and increased intracranial pressure; risk of emergent reactions (hallucinations, delirium); potential for abuse and dependence.
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.
Monitor blood pressure and cardiac function; use with caution in patients with hypertension, heart failure, or increased intracranial pressure; emergence reactions may occur; laryngospasm risk; respiratory depression.
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.
Hypersensitivity to ketamine; conditions where elevated blood pressure or intracranial pressure would be dangerous (e.g., severe hypertension, cerebral hemorrhage); severe coronary artery disease; history of psychotic disorders.
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; avoid alcohol for 24 hours due to additive CNS depression.
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.
First trimester: Limited human data; animal studies show no teratogenicity. Second/third trimester: Use only if clearly needed; may cause neonatal respiratory depression, hypotonia, and altered neurobehavior if used near delivery.
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 into breast milk in low amounts; M/P ratio unknown. Use caution, especially with repeated doses or in neonates with hepatic impairment.
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 adjustment required for pregnancy; consider reduced dose due to increased volume of distribution and clearance in late pregnancy. Use lowest effective dose.
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.
Ketamine (Ketalar) produces dissociative anesthesia with potent analgesia. Onset of action is rapid (30 seconds IV, 5 minutes IM). Emergence reactions (hallucinations, delirium) can be mitigated with benzodiazepines. Contraindicated in patients with hypertension, aneurysms, or increased intracranial pressure due to sympathomimetic effects. Use with caution in patients with psychosis or thyroid disorders.
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 may experience vivid dreams or hallucinations as the medication wears off; this is common and can be reduced with other medications.,Do not drive, operate machinery, or make important decisions for at least 24 hours after receiving ketamine.,Avoid alcohol and other sedatives for 24 hours after administration.,Inform your healthcare provider if you have high blood pressure, heart disease, or a history of psychosis.
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 KETALAR vs FLUOTHANE, answered by our medical review team.
KETALAR is a General Anesthetic that works by Noncompetitive NMDA receptor antagonist; inhibits glutamate activity, modulates opioid receptors, and interacts with other neurotransmitter systems.. 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 KETALAR 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 KETALAR is: 1-4.5 mg/kg IV or 6.5-13 mg/kg IM for induction of anesthesia; 0.1-0.5 mg/kg/min IV infusion for maintenance.. 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 KETALAR 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. KETALAR is classified as Category C. First trimester: Limited human data; animal studies show no teratogenicity. Second/third trimester: Use only if clearly needed; may cause neonatal respiratory depression, hypotonia. 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.