Phenibut, sold under the brand names Anvifen, Fenibut, and Noofen among others, is a central nervous system depressant with anxiolytic and stimulant effects which is used in the treatment of anxiety, insomnia, and for a variety of other indications. Phenibut HCL Powder is a nootropic compound and derivative of the naturally occurring inhibitory neurotransmitter known as Gamma-Aminobutyric acid, or GABA. It differs by the addition of a phenyl grouping to the GABA structure. Phenibut has a molar mass of 179.216 g/mol and a chemical structure of C10H13NO2. It is usually taken by mouth as a tablet, but can also be given as an intravenous infusion.