The active ingredient halothane is a narcotic that is usually administered by inhalation. The substance appears in the form of a liquid that is usually colorless and nonflammable. In modern times, the drug halothane is virtually no longer used in industrialized countries. Here, the drug halothane has been replaced for the most part by other preparations. In the third world as well as various emerging countries, however, the active ingredient halothane is still used as a narcotic.
What is halothane?
Basically, the drug halothane is a so-called halogenated hydrocarbon. The development of the drug halothane was commissioned in 1951 by Imperial Chemical Industries and manufactured by Charles Suckling. Since 1956 it was used as an anesthetic. The special feature of the drug is that it is to be taken via the respiratory tract. Nowadays, the active ingredient halothane is largely replaced by other, more modern types of anesthetics in the USA as well as Europe. These include, for example, the drugs sevoflurane, isoflurane and desflurane. The industrial production of halothane is usually based on the substance trichloroethylene. This is converted together with hydrogen fluoride in the presence of antimony trichloride. The chemical reaction to the substance 2-chloro-1,1,1-trifluoroethane takes place at about 130 degrees Celsius. In the next step, a further reaction is initiated. Here, the reaction product from the first pass is brought together with bromine at a temperature of 450 degrees Celsius. As a result, the substance halothane is formed. Basically, the active medical ingredient halothane is a so-called racemate. The substance appears as a clear and heavy liquid that is virtually insoluble in water. In the context of therapy with the drug halothane, it should be noted that malignant hyperthermia may occur.
Pharmacologic action
The drug halothane is characterized by a characteristic mode of action on the human organism. Primarily, it has a strong analgesic and narcotic effect. In addition, to a certain extent, it has a relaxing effect on the muscles. In principle, the drug halothane is used in the form of a liquid. This liquid is characterized by a sweetish odor. In addition, the drug has a high sensitivity to light, which is why it is usually stored in brown or dark bottles. In addition, halothane is highly soluble in fat and blood. In this way, the active ingredient spreads rapidly in the human blood and, accordingly, also floods out again quickly. For this reason, it is ideally suited as an anesthetic. It is also important that the drug does not form explosive compounds. This makes it possible to combine halothane with the substance nitrous oxide. Thus, the dose of the drug can be reduced. In principle, the drug halothane is a highly potent narcotic for inhalation.
Medical application and use
Halothane is used in the vast majority of cases as part of anesthesia. In this case, the patient inhales the active substance, so that the substance is absorbed through the respiratory tract and subsequently passes into the blood via the lungs. During therapy with the drug, it must be taken into account that halothane is characterized by a relatively small anesthetic range. Depending on the dose administered, there is also a drop in blood pressure. In addition, the active ingredient halothane affects the myocardium, which consequently reacts more sensitively to catecholamines. This increases the risk of tachyarrhythmias in the affected patient. It should also be noted that liver bromide ions are released during metabolism of the drug halothane. In high concentrations, these ions exert a toxic effect. Under certain circumstances, they cause allergic reactions or weaken the immune system. In particularly rare cases, patients develop a so-called halothane hepatitis after administration of the drug halothane, which is an allergic reaction. For this reason, there is a recommendation to treat people with the active substance halothane only at intervals of three months. Basically, not only the respective patient is exposed, but especially also the treating staff. In modern times, however, halothane is used less and less frequently.Instead, so-called halogenated ethers are increasingly used, for example isoflurane, enflurane, and sevoflurane.
Risks and side effects
Various side effects are possible from administration of the drug halothane. For example, intracranial pressure is increased. Depending on the dose, respiratory depression is also possible. For this reason, so-called assisted ventilation is often used during anesthetic administration. In addition, the drug halothane may promote the development of malignant hyperthermia. If this condition is not treated, mortality is relatively high. In particularly rare cases, halothane hepatitis occurs about one week after anesthesia with halothane. It is accompanied by symptoms such as chills, fever, pain in the joints, jaundice, and blood clotting disorders. The reason is probably toxic metabolites of the pharmacological agent halothane.
