Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
KETAMINE HYDROCHLORIDE 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; also interacts with opioid receptors, monoaminergic receptors, and voltage-gated calcium channels.
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,Sedation,Analgesic for acute pain,Treatment-resistant depression (off-label),Status epilepticus (off-label)
Induction and maintenance of general anesthesia,Off-label: Use for status asthmaticus (rarely)
Induction: 1-2 mg/kg IV, 0.5-1 mg/kg/min IV infusion for maintenance. Dissociative sedation: 1-1.5 mg/kg IV or 3-4 mg/kg IM. Pain management: 0.1-0.5 mg/kg IV bolus followed by 0.1-0.4 mg/kg/h IV infusion.
Induction: 0.5-3% halothane in oxygen or nitrous oxide/oxygen; maintenance: 0.5-1.5%.
Terminal elimination half-life of ketamine is 2.5–3 hours; norketamine half-life is approximately 4 hours. Context: Prolonged elimination may occur with hepatic impairment or high-dose infusions.
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.
Hepatic via CYP2B6 and CYP3A4; major metabolite norketamine.
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.
Ketamine is primarily metabolized in the liver via N-demethylation to norketamine. Renal excretion accounts for approximately 90% of the dose, with 4% as unchanged drug, 16% as norketamine, and the remainder as conjugated metabolites. Fecal excretion is minimal (<5%).
Primarily exhaled unchanged via the lungs; negligible renal (0.5% as metabolites) and fecal elimination.
Approximately 47% bound to plasma proteins, primarily albumin and alpha-1-acid glycoprotein.
~40-50% bound to albumin.
Volume of distribution is 3–5 L/kg, indicating extensive tissue distribution and accumulation in lipid-rich tissues (e.g., brain, adipose).
2-5 L/kg; indicates extensive tissue distribution, particularly in adipose and brain.
Oral: 17–20% (extensive first-pass metabolism); Intranasal: 45–50%; IM: 93%; Rectal: 25–50%; IV: 100%.
Inhalation: 100% (administered as gas); no other relevant routes.
No specific GFR-based dose adjustment is required. Use with caution in severe renal impairment (Cr Cl <30 m L/min) due to potential accumulation of active metabolite norketamine; monitor for prolonged effects.
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 25-50% and titrate to effect. Child-Pugh Class C: Contraindicated or use with extreme caution; reduce dose by 50-75% and monitor closely.
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, 3-4 mg/kg IM. Maintenance: 0.5-1 mg/kg IV or IM as needed. Procedural sedation: 0.5-1 mg/kg IV, may repeat. Continuous infusion: 0.2-0.5 mg/kg/h. Maximum single dose: 2 mg/kg IV, 4 mg/kg IM.
Induction: 0.5-2% halothane in oxygen; maintenance: 0.3-1%. Dose based on response.
Reduce initial dose by 20-50% due to decreased clearance and increased sensitivity. Titrate slowly to effect. Monitor for cardiovascular and cognitive adverse effects closely.
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.
Emergence reactions (hallucinations, confusion),Hemodynamic instability (hypertension, tachycardia),Increased intracranial pressure,Respiratory depression,Urinary tract toxicity with chronic use
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 is dangerous (e.g., aneurysms, uncontrolled hypertension),Severe coronary artery disease,Increased intracranial pressure (relative)
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 significant food interactions; grapefruit juice may increase ketamine levels via CYP3A4 inhibition, but clinical relevance is unclear; avoid alcohol consumption due to additive sedative effects.
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.
Ketamine crosses the placenta. First trimester: Limited human data, animal studies show developmental toxicity at high doses; avoid unless essential. Second/Third trimester: Use only for indicated procedures (e.g., surgical anesthesia, procedural sedation) as maternal hypoxia may risk fetus; potential for neonatal respiratory depression if used near delivery. Neonatal effects: Possible altered neurodevelopment; consider risk-benefit.
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.
Ketamine enters breast milk; milk-to-plasma ratio approximately 0.8-1.5. Limited data; low absolute dose (<2% maternal weight-adjusted dose). Caution with repeated high doses; monitor infant for sedation, feeding difficulties. American Academy of Pediatrics: compatible with breastfeeding after single doses.
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.
Pregnancy may alter pharmacokinetics: increased volume of distribution may require higher initial doses; decreased plasma protein binding may increase free fraction. However, standard dosing guidelines for procedures apply; titrate to effect. Use lowest effective dose due to potential neurotoxicity. Caution with repeated use or long infusions.
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 produces dissociative anesthesia with preserved airway reflexes and respiratory drive at sub-anesthetic doses; monitor for emergence reactions (hallucinations, delirium) especially in adults; co-administer a benzodiazepine to reduce psychotomimetic effects; use with caution in patients with hypertension, tachycardia, or increased intracranial pressure; can cause increased secretions, consider an anticholinergic like glycopyrrolate; analgesic doses are sub-dissociative (0.1-0.5 mg/kg IV); contraindicated in patients with severe coronary artery disease or recent cerebrovascular accident.
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 feel detached from your body or have unusual dreams during recovery; this is normal and temporary.,Do not drive or operate machinery for 24 hours after receiving ketamine.,Avoid alcohol and other sedatives for at least 24 hours after treatment.,Report any hallucinations, confusion, or difficulty breathing to your healthcare provider immediately.,For nasal spray (esketamine), follow instructions for administration and avoid eating or drinking for 30 minutes after use.
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.
"Butabarbital, a barbiturate, induces cytochrome P450 (CYP) enzymes, enhancing the hepatic metabolism of ketamine, a dissociative anesthetic primarily metabolized by CYP3A4 and CYP2B6. This interaction reduces ketamine's systemic exposure and anesthetic efficacy, potentially leading to suboptimal sedation or anesthesia. Additionally, concurrent use may increase the risk of respiratory depression and hypotension due to additive central nervous system (CNS) depressant effects."
"The combination of ketamine and diamorphine can lead to additive central nervous system (CNS) depression and respiratory depression, increasing the risk of hypoxia, sedation, and respiratory arrest. Ketamine, an NMDA receptor antagonist, enhances opioid-induced analgesia but also potentiates the adverse effects of diamorphine, including hypotension and bradycardia. Patients may experience profound sedation, confusion, and cardiovascular instability, particularly at higher doses or in opioid-naive individuals."
"Ketamine, an NMDA receptor antagonist, may inhibit cytochrome P450 3A4 (CYP3A4) activity, which is responsible for the 25-hydroxylation of cholecalciferol (vitamin D3) to calcidiol (25-hydroxyvitamin D). This inhibition can reduce the conversion of cholecalciferol to its active form, potentially leading to decreased vitamin D levels and impaired calcium homeostasis. Clinically, this may increase the risk of vitamin D deficiency, contributing to bone demineralization, hypocalcemia, or secondary hyperparathyroidism in patients receiving long-term or high-dose ketamine therapy."
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about KETAMINE HYDROCHLORIDE vs FLUOTHANE, answered by our medical review team.
KETAMINE HYDROCHLORIDE is a General Anesthetic that works by Noncompetitive NMDA receptor antagonist; also interacts with opioid receptors, monoaminergic receptors, and voltage-gated calcium channels.. 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 KETAMINE HYDROCHLORIDE 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 KETAMINE HYDROCHLORIDE is: Induction: 1-2 mg/kg IV, 0.5-1 mg/kg/min IV infusion for maintenance. Dissociative sedation: 1-1.5 mg/kg IV or 3-4 mg/kg IM. Pain management: 0.1-0.5 mg/kg IV bolus followed by 0.1-0.4 mg/kg/h IV infusion.. 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 KETAMINE HYDROCHLORIDE 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. KETAMINE HYDROCHLORIDE is classified as Category C. Ketamine crosses the placenta. First trimester: Limited human data, animal studies show developmental toxicity at high doses; avoid unless essential. Second/Third trimester: Use on. 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.