Overview
Halothane is a volatile general inhalation anesthetic used for induction and maintenance of general anesthesia. It provides rapid induction and recovery, bronchodilation, and muscle relaxation. Due to its association with rare but severe hepatotoxicity (halothane hepatitis), its use has declined in favor of newer agents in many countries, though it remains available in some regions including Jordan.
Mechanism of Action
Halothane acts as a general anesthetic by potentiating GABA-A and glycine receptor activity in the central nervous system, leading to neuronal hyperpolarization and inhibition. It also inhibits NMDA glutamate receptors and modulates other ion channels, resulting in dose-dependent CNS depression, amnesia, analgesia, and immobility.
Indications
- Induction and maintenance of general anesthesia
- Provision of bronchodilation in patients with reactive airway disease
Dosage
Administered via calibrated vaporizer. Induction: 1-4% halothane in oxygen or nitrous oxide/oxygen mixture. Maintenance: 0.5-2% concentration. Dosage must be individualized based on patient response, with careful monitoring of vital signs and anesthetic depth.
Black Box Warning
Halothane has been associated with rare cases of fatal hepatic necrosis. The risk increases with multiple exposures, particularly within short time intervals. Unexplained fever, jaundice, or elevated liver enzymes following halothane exposure should be thoroughly investigated.
Contraindications
- Known hypersensitivity to halothane or other halogenated anesthetics
- Personal or family history of malignant hyperthermia
- Unexplained liver dysfunction following previous halothane exposure
- Porphyria
Side Effects
- Hepatotoxicity (elevated transaminases, jaundice, hepatic necrosis)
- Malignant hyperthermia
- Cardiac arrhythmias (bradycardia, ventricular arrhythmias)
- Hypotension
- Respiratory depression
- Nausea and vomiting
- Shivering during recovery
- Postoperative drowsiness
Interactions
- Aminophylline/theophylline: Increased risk of cardiac arrhythmias
- Catecholamines (epinephrine, norepinephrine): Increased risk of ventricular arrhythmias
- Non-depolarizing muscle relaxants: Potentiated neuromuscular blockade
- Opioids: Enhanced respiratory and CNS depression
- Beta-blockers: Enhanced bradycardia and hypotension
- MAO inhibitors: Unpredictable blood pressure responses