Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
KETAMINE HCL 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; blocks glutamate binding, and modulates 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,Procedural sedation and analgesia,Treatment-resistant depression (off-label),Acute pain management (off-label)
Induction and maintenance of general anesthesia,Off-label: Use for status asthmaticus (rarely)
Induction: 1-2 mg/kg IV; Maintenance: 0.5-1 mg/kg IV or 10-30 mcg/kg/min IV infusion; Subanesthetic: 0.1-0.5 mg/kg IV; Analgesic: IM 2-4 mg/kg; Intranasal 1-3 mg/kg. Frequency: single doses or continuous infusion per clinical need.
Induction: 0.5-3% halothane in oxygen or nitrous oxide/oxygen; maintenance: 0.5-1.5%.
Terminal elimination half-life: 2–4 hours (alpha: 10–15 min, beta: 2.5–4 hr); prolonged in hepatic impairment and with repeated dosing (up to 12–24 hr for active metabolite norketamine).
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; primarily via CYP3A4 and CYP2B6 to norketamine (active metabolite), then further metabolized by CYP2B6 and CYP2A6.
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, hydroxylated derivatives) and 4% unchanged; biliary/fecal: 3%; minor pulmonary exhalation.
Primarily exhaled unchanged via the lungs; negligible renal (0.5% as metabolites) and fecal elimination.
47% bound primarily to albumin and alpha-1-acid glycoprotein.
~40-50% bound to albumin.
2–4 L/kg (large distribution due to high lipophilicity; deep tissue compartments).
2-5 L/kg; indicates extensive tissue distribution, particularly in adipose and brain.
IM: 93%; intranasal: 45–50%; oral: 17–20% (extensive first-pass metabolism).
Inhalation: 100% (administered as gas); no other relevant routes.
No dose adjustment required for mild to moderate renal impairment (e GFR >=30 m L/min). Severe renal impairment (e GFR <30 m L/min): use with caution; no specific dosing guidelines; consider reduced doses and monitor for prolonged effects.
No dose adjustment required for renal impairment; halothane is minimally excreted renally.
Child-Pugh A: no adjustment. Child-Pugh B: consider 50% dose reduction. Child-Pugh C: avoid use or use extreme caution with significant dose reduction (e.g., 75% reduction) 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; Maintenance: 0.5-1 mg/kg IV bolus or 5-20 mcg/kg/min IV infusion; IM: 2-5 mg/kg; Intranasal: 1-3 mg/kg. For procedural sedation: IV 0.5-1 mg/kg over 2-3 minutes; additional doses 0.25-0.5 mg/kg as needed. Weight-based dosing per kg.
Induction: 0.5-2% halothane in oxygen; maintenance: 0.3-1%. Dose based on response.
Elderly patients: start with lowest effective doses; typical induction dose 0.5-1 mg/kg IV; reduce maintenance infusion rates (e.g., 5-10 mcg/kg/min); monitor for increased sensitivity, cognitive impairment, and cardiovascular effects; consider dose reduction of 25-50% compared to younger adults.
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 (delirium, hallucinations) can occur; minimize with benzodiazepines.,Hemodynamic instability: increased heart rate and blood pressure (contraindicated in hypertension/aneurysm).,Potential for abuse and dependence; schedule III controlled substance.,Laryngospasm and respiratory depression, especially at higher doses.,Increased intracranial pressure and intraocular pressure.
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 or any component,Conditions where significant blood pressure elevation is hazardous (e.g., aneurysms, uncontrolled hypertension),Severe coronary artery disease,Increased intracranial pressure or intraocular pressure,Pregnancy (only if benefit outweighs risk)
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 known food interactions. Avoid alcohol and grapefruit juice due to potential CYP3A4 inhibition affecting metabolism.
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.
Fetal risk cannot be ruled out; animal studies show adverse effects at maternal toxic doses. Human data limited; avoid in first trimester unless benefits outweigh risks. Potential for fetal neurotoxicity in third trimester; use only if clearly needed.
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.
M/P ratio unknown; ketamine enters breast milk in low amounts. Limited data; monitor infant for sedation. Weigh benefits against potential risks.
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; consider increased volume of distribution and clearance. Use lowest effective dose; titrate to desired effect with careful monitoring.
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 spontaneous respiration. Onset is rapid (30 seconds IV, 5 minutes IM). Emergence reactions (hallucinations, delirium) can be mitigated with benzodiazepines. Contraindicated in patients with elevated intracranial or intraocular pressure, hypertension, and severe coronary artery disease. Use with caution in psychiatric disorders. Subanesthetic doses are used for treatment-resistant depression and acute pain.
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 confusion as the medication wears off.,Do not drive or operate machinery for at least 24 hours after receiving ketamine.,Avoid alcohol and other sedatives for 24 hours following treatment.,Inform your doctor if you have a history of high blood pressure, glaucoma, or psychiatric illness.,This medication may cause changes in perception or feeling of detachment during administration.
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 HCL vs FLUOTHANE, answered by our medical review team.
KETAMINE HCL is a General Anesthetic that works by Noncompetitive NMDA receptor antagonist; blocks glutamate binding, and modulates 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 HCL 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 HCL is: Induction: 1-2 mg/kg IV; Maintenance: 0.5-1 mg/kg IV or 10-30 mcg/kg/min IV infusion; Subanesthetic: 0.1-0.5 mg/kg IV; Analgesic: IM 2-4 mg/kg; Intranasal 1-3 mg/kg. Frequency: single doses or continuous infusion per clinical need.. 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 HCL 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 HCL is classified as Category C. Fetal risk cannot be ruled out; animal studies show adverse effects at maternal toxic doses. Human data limited; avoid in first trimester unless benefits outweigh risks. Potential . 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.