Anaes · Volatile & inhalational agents

Halothane

Also known as 2-bromo-2-chloro-1,1,1-trifluoroethane · CF3-CHBrCl · Fluothane · Historical standard volatile · Catecholamine-sensitising volatile · Halothane hepatitis agent

Halothane (2-bromo-2-chloro-1,1,1-trifluoroethane, CF3-CHBrCl) is the historical standard volatile anaesthetic, introduced in 1956 and the agent against which every modern volatile is still measured. It is defined by five exam-critical ideas. Its minimum alveolar concentration (MAC) of 0.75 percent is the lowest and therefore the most potent of the common volatile agents, while its blood-gas partition coefficient of 2.4 gives a slower onset and offset than sevoflurane, isoflurane or desflurane (agent constants standard teaching). It is non-pungent with a pleasant smell, which made it the classic agent for inhalational induction in children. It is a potent bronchodilator, exploited historically in refractory status asthmaticus. It markedly sensitises the myocardium to catecholamines, so concurrent adrenaline infiltration can precipitate ventricular arrhythmias. And it causes the type 2 (immune-mediated) halothane hepatitis — massive hepatic necrosis, frequently fulminant, with an incidence between 1 in 3500 and 1 in 35,000 and prevention resting on avoiding re-exposure after pyrexia or jaundice and on family history — driven by cytochrome P450 2E1 oxidation to trifluoroacetylated-protein target antigens, which together with its catecholamine arrhythmogenicity, its role as a malignant-hyperthermia trigger, and its ozone-depleting chlorofluorocarbon chemistry drove its withdrawal from developed-world practice as sevoflurane rose in the 1990s. Built on the halothane-toxicity overview (Gyorfi 2023), the halothane-hepatitis incidence and prevention review (Neuberger 1990), the CYP2E1-autoantigen mechanism study (Eliasson 1996), the halothane-hepatitis forms review (Ray 1991), the National Halothane Study historical narrative (Forrest 2025), the European Malignant Hyperthermia Group 2025 diagnostic guidelines (Ruffert 2026), the novel RYR1-variant case evaluation (Tracy 2025), the network meta-analysis of anaesthetics on cardiac repolarisation (Cai 2023), the halogenated-anaesthetic greenhouse-gas analysis (Talbot 2025), and the isoflurane-in-status-asthmaticus case report (Gill 2022).