FLUOTHANE

Clinical safety rating: caution

Comprehensive clinical and safety monograph for FLUOTHANE (FLUOTHANE).

How it works

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.

What the body does with it

Metabolism	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.
Excretion	Primarily exhaled unchanged via the lungs; negligible renal (0.5% as metabolites) and fecal elimination.
Half-life	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.
Protein binding	~40-50% bound to albumin.
Volume of Distribution	2-5 L/kg; indicates extensive tissue distribution, particularly in adipose and brain.
Bioavailability	Inhalation: 100% (administered as gas); no other relevant routes.
Onset of Action	Inhalation: within 30-60 seconds (induction); dose-dependent.
Duration of Action	Inhalation: 5-10 minutes after discontinuation for emergence; prolonged with higher cumulative doses.

Classification & Brands

Dosing & administration

Induction: 0.5-3% halothane in oxygen or nitrous oxide/oxygen; maintenance: 0.5-1.5%.

Dosage form	LIQUID
Renal impairment	No dose adjustment required for renal impairment; halothane is minimally excreted renally.
Liver impairment	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.
Pediatric use	Induction: 0.5-2% halothane in oxygen; maintenance: 0.3-1%. Dose based on response.
Geriatric use	Reduce induction concentration to 0.5-1% and maintenance to 0.5% due to increased sensitivity and slower clearance.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for FLUOTHANE (FLUOTHANE).

Breastfeeding	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.
Teratogenic Risk	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.

Warnings & precautions

■ FDA Black Box Warning

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.

Side Effect Profile

Serious Effects

Absolute Contraindications

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).

Clinical Precautions

Precautions

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.

Clinical Tips & Counseling

Drug interactions

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FLUOTHANE

Clinical safety rating: caution

Comprehensive clinical and safety monograph for FLUOTHANE (FLUOTHANE).

How it works

What the body does with it

Metabolism	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.
Excretion	Primarily exhaled unchanged via the lungs; negligible renal (0.5% as metabolites) and fecal elimination.
Half-life	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.
Protein binding	~40-50% bound to albumin.
Volume of Distribution	2-5 L/kg; indicates extensive tissue distribution, particularly in adipose and brain.
Bioavailability	Inhalation: 100% (administered as gas); no other relevant routes.
Onset of Action	Inhalation: within 30-60 seconds (induction); dose-dependent.
Duration of Action	Inhalation: 5-10 minutes after discontinuation for emergence; prolonged with higher cumulative doses.

Classification & Brands

Dosing & administration

Induction: 0.5-3% halothane in oxygen or nitrous oxide/oxygen; maintenance: 0.5-1.5%.

Dosage form	LIQUID
Renal impairment	No dose adjustment required for renal impairment; halothane is minimally excreted renally.
Liver impairment	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.
Pediatric use	Induction: 0.5-2% halothane in oxygen; maintenance: 0.3-1%. Dose based on response.
Geriatric use	Reduce induction concentration to 0.5-1% and maintenance to 0.5% due to increased sensitivity and slower clearance.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for FLUOTHANE (FLUOTHANE).

Breastfeeding	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.
Teratogenic Risk	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.