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Flurothyl (Indoklon) is a volatile liquid agent from the halogenated ether family, a congener of inhaled anaesthetic agents such as diethyl ether. At higher doses, after inducing loss of consciousness, these agents elicit a grand mal seizure, acting as both stimulant and convulsant. Several compounds related to the halogenated ether anesthetics have similar convulsant effects. They have been helpful in studying the mechanism of action of these drugs.
Flurothyl treatment in psychiatric patients In 1953 the Maryland pharmacologist J. C. Krantz experimented with flurothyl to induce seizures in psychiatric patients as an alternative treatment for electroconvulsive treatment (electroshock). Flurothyl was given the proprietary name “Indoklon.” A clear and stable liquid, it has a mild ethereal odor whose vapors are non-flammable. It is excreted from the body by the lungs in an unchanged state. [6-8]
Flurothyl was injected into a plastic container in a tight fitting face mask. The patient inhaled a mixture of vapor and air, and expired air was forced into a charcoal adsorbent via a one-way valve. Oxygen was administered simultaneously. Flurothyl inhalations were first conducted without sedation or muscle paralysis.[9,10] Premedication with pentothal and succinylcholine chloride, as is customary in ECT, was tested and found safe. 
Four random assignment treatment studies found the clinical results for flurothyl to be as effective as those of ECT. [12-15] Flurothyl treatments were administered on the same schedules as ECT. In some patients who had not responded to ECT, flurothyl treatment produced improvement. 
The flurothyl treated patients showed less amnesia and confusion during the course of treatment with better patient acceptance. A detailed study comparing flurothyl and ECT in patients with severe endogenous depression, reported the degree of anterograde amnesia to be similar, but the degree of retrograde amnesia was much lower after flurothyl.  Psychological tests showed memory impairments at the fourth week of treatment, and memory improvement two weeks after the last treatment, with no measurable differences between the treatments.
Equal degrees of EEG slow wave increases were recorded in flurothyl and electrical induced seizures.  Oximetric and ECG studies showed comparable heart rate increases with occasional rhythmic irregularities. 
Flurothyl induced seizures were deemed clinically equal to electrical seizures with lesser effects on cognition and memory. An editorial in the Journal of the American Medical Association in 1966 encouraged its use. 
An injectable form of flurothyl was formulated.  The clinical results were the same as with inhaled flurothyl. 
The administration of flurothyl was more difficult than that of electrical inductions. The ethereal odors that quickly pervaded the treatment room frightened the treatment team members who saw how quickly, after a few breaths, the seizure was induced in patients. And the cost was greater. Flurothyl use was discarded in psychiatric patients for problems in administration, not inefficacy or risk.
Considering the persisting stigma and complaints of memory loss that continue to plague ECT, re-appraisal of flurothyl inhalation treatment in modern anesthesia suites has been encouraged. 
Its principal use in scientific studies is to induce seizures in animals.
See also: Theories of general anaesthetic action. Electroconvulsive therapy
See also: Theories of general anaesthetic action.
1. Rose, L, Watson, A (1967). "Flurothyl (Indoklon). Experience with an inhalational convulsant agent". Anaesthesia 22 (3): 425–34. PMID 4951597.
2. Koblin DD, Chortkoff BS, Laster MJ, et al. (December 1994). "Polyhalogenated and perfluorinated compounds that disobey the Meyer-Overton hypothesis". Anesthesia and Analgesia 79 (6): 1043–8. doi:10.1213/00000539-199412000-00004. PMID 7978424.
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17. Fink M. Convulsive Therapy: Theory and Practice. New York: Raven Press, 1979.
18.A convulsant agent for psychiatric use. Flurothyl (Indoklon). JAMA: the Journal of the American Medical Association 196 (1): 29–30. 1966. doi:10.1001/jama.196.1.29. PMID 4379572.
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21. Cooper K, Fink M. The chemical induction of seizures in psychiatric therapy: Were flurothyl (Indoklon) and pentylenetetrazol (Metrazol) abandoned prematurely? J Clinical Psychopharmacology (in press 2014).