Last reviewed September 2026
Phenibut is a synthetic drug closely related to GABA, the brain’s main calming messenger. Its chemical name is beta-phenyl-gamma-aminobutyric acid, often shortened to β-phenyl-GABA. On labels and in shops it also shows up as fenibut, phenigam, phenyl-GABA, Noofen or Anvifen.
Where it came from
Chemists working under V. V. Perekalin at the Herzen Pedagogical Institute in Leningrad (now St. Petersburg) made the compound, and it has been used as a medicine in Russia since the 1960s. Russian doctors prescribe it for anxiety, insomnia and several other conditions. Some other former Soviet countries use it medically too.
You may have read that phenibut went up in Soviet cosmonauts’ medical kits. The story gets repeated a lot, but a 2021 review prepared for the World Health Organization didn’t find documentation to back it up.
How it works
Phenibut acts on GABA-B receptors, the same target as the muscle relaxant baclofen. It also binds to the alpha-2-delta part of calcium channels on nerve cells, which is how gabapentin and pregabalin work. That puts it in a family of drugs that slow down nerve signaling and cause drowsiness and calm.
The body adapts to drugs like this. With regular use, the same amount does less, and stopping can bring on withdrawal. More on that on our safety and withdrawal pages.
How it ended up in U.S. stores
Phenibut has never been approved as a medicine in the United States. For years it was sold online and in some shops as a “nootropic” or dietary supplement, often marketed for sleep, stress or social anxiety.
In April 2019 the FDA said phenibut doesn’t fit the legal definition of a dietary ingredient, so any supplement that lists it is misbranded. It still turns up in capsules, powders, drinks and gummies, and several states have since banned or restricted it. See Is phenibut legal? for the details.
Sources
- FDA, Phenibut in Dietary Supplements
- World Health Organization, Pre-Review Report: Phenibut, 44th Expert Committee on Drug Dependence, 2021
- Bonnet U. et al., Phenibut: an illegal food supplement with psychotropic effects and health risks, Deutsches Ärzteblatt International, 2024
- Lapin I., Phenibut (β-phenyl-GABA): a tranquilizer and nootropic drug, CNS Drug Reviews, 2001