Fenadiazole (), also known as phénadiazole () and sold under the brand names Hypnazol, Eudormil, and Viodor, is a hypnotic and sedative medication which has been used to treat insomnia but is no longer marketed. It is described as a non-barbiturate hypnotic with marked or profound hypnotic and sedative properties in animals, variable hypnotic effects in humans (rapidly inducing sleep for 6 to 8hours), additional anticonvulsant, antithermal, and spasmolytic effects, and a generally well-tolerated profile in humans (at an average dosage of 200mg/day). Abstract: 2-(o-Hydroxyphenyl)-1,3,4-oxadiazole (I) rapidly induced sleep for a duration of 6-8 hrs. in man. I is prepd. in 92.5% yield by refluxing a mixt. of 431 g. salicylic acid hydrazide, 800 cc. HC(OEt)3, and 2350 cc. xylene. Approx. 390 g. EtOH is distd.; the remaining hot soln. is filtered and cooled to 0°. Crystals of I formed are washed with xylene, then with petr. ether and dried. Given intraperitoneally, L.D.50 is 940 mg./kg. for mice; 910 mg./kg. for the rats; orally it is 4.72 mg./kg. for mice. Abstract: The title compds., possessed marked hypnotic and sedative properties, were prepd. by heating salicylic acid hydrazide (I) with an alkyl orthoformate (excess) and removing the alc. corresponding to the alkyl group of the selected orthoformate by continuous distn. Thus, 431 g. I, 800 ml. ethyl orthoformate, and 2350 ml. xylene was refluxed while stirring and the alc. removed continuously by distn. After 6 hrs., the hot soln. was filtered, and cooled (0°) to give 2-(o-hydroxyphenyl)-1,3,4-oxadiazole (II), m. 109-10°, in 92.5% yield. Derivs. of II were obtained by replacing the H atom of the phenolic hydroxyl by metals. The drug was synthesized, pharmacologically characterized, patented, and marketed by the French pharmaceutical company Laboratoires Jacques Logeais between 1960 and 1962. As a hypnotic and sedative, fenadiazole has a unique oxadiazole-based chemical structure. It may be chemically related to certain other hypnotics and sedatives with atypical chemical structures. Fenadiazole was encountered online as a novel designer drug in 2025, and has been added to the controlled drugs list in Hungary.Társadalmi egyeztetés az új pszichoaktív anyagok szabályozásáról.
See also Phemerazole
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