halothan

Halothane, also known as halothan in some languages, is a volatile inhalational anesthetic used for general anesthesia. Its chemical name is 2-bromo-2-chloro-1,1,1-trifluoroethane, with the molecular formula C2HBrClF3. It is supplied as a clear, nonflammable liquid that is vaporized for inhalation.

Pharmacology: Halothane is a potent anesthetic with a relatively low blood-gas partition coefficient compared with older agents, and a MAC around 0.7–0.8%. It causes rapid loss of consciousness to a surgical level of anesthesia. It also causes dose-dependent depression of myocardial contractility and systemic vasodilation, which lowers blood pressure. It can sensitize the heart to catecholamines, increasing the risk of arrhythmias. It also reduces cerebral metabolic rate while increasing cerebral blood flow due to vasodilation. Analgesia is limited; adjuncts are often required.

Metabolism and safety concerns: Approximately 20–25% of halothane is metabolized in the liver to reactive trifluoroacetyl derivatives that can bind hepatic proteins and trigger immune-mediated hepatitis in some individuals. Halothane-associated hepatitis is rare but potentially fatal and risk is higher with repeated exposure or in patients with prior hepatic disease. Halothane also poses a risk of malignant hyperthermia in susceptible individuals, though the incidence is low compared to other agents. Because of these risks, halothane usage has declined and it is less commonly used today, especially outside resource-limited settings.

History and current use: Halothane was introduced in the 1950s and marketed as Fluothane by Imperial Chemical Industries. It was widely used for general anesthesia in the second half of the 20th century. With the development of newer volatile anesthetics such as isoflurane, sevoflurane, and desflurane, halothane has been largely supplanted due to safety and recovery advantages. It remains in use in some parts of the world or for specific indications, under appropriate monitoring.