[7] In rare cases, repeated exposure to halothane in adults was noted to result in severe liver injury.

[19] Concern for hepatitis resulted in a dramatic reduction in the use of halothane for adults and it was replaced in the 1980s by enflurane and isoflurane.

[24] Halothane sensitises the heart to catecholamines, so it is liable to cause cardiac arrhythmia, occasionally fatal, particularly if hypercapnia has been allowed to develop.

[5] Similarly, in common with the other potent inhalational agents, it relaxes uterine smooth muscle and this may increase blood loss during delivery or termination of pregnancy.

[27] The National Institute for Occupational Safety and Health (NIOSH) has set a recommended exposure limit (REL) of 2 ppm (16.2 mg/m3) over 60 minutes.

[31] Halothane (2-bromo-2-chloro-1,1,1-trifluoroethane) is a dense, highly volatile, clear, colourless, nonflammable liquid with a chloroform-like sweet odour.

[citation needed] The commercial synthesis of halothane starts from trichloroethylene, which is reacted with hydrogen fluoride in the presence of antimony trichloride at 130 °C to form 2-chloro-1,1,1-trifluoroethane.

Attempts to find anesthetics with less metabolism led to halogenated ethers such as enflurane and isoflurane.

[36] Small amounts of trifluoroacetic acid can be formed from both halothane and isoflurane metabolism and possibly accounts for cross sensitization of patients between these agents.

[37][38] The main advantage of the more modern agents is lower blood solubility, resulting in faster induction of and recovery from anaesthesia.

[39] Halothane was first synthesized by C. W. Suckling of Imperial Chemical Industries in 1951 at the ICI Widnes Laboratory and was first used clinically by M. Johnstone in Manchester in 1956.

But halothane, which required specialist knowledge and technologies for safe administration, also afforded British anaesthesiologists the opportunity to remake their speciality as a profession during a period, when the newly established National Health Service needed more specialist consultants.

In many parts of the world it has been largely replaced by newer agents since the 1980s but is still widely used in developing countries because of its lower cost.

Its lack of airway irritation made it a common inhalation induction agent in pediatric anesthesia.

[20] Owing to the presence of covalently bonded fluorine, halothane absorbs in the atmospheric window and is therefore a greenhouse gas.