Phenibut powder can probably best be described as a supplement, although it doesn’t necessarily have a rigid classification in the U.S. It is an uncontrolled substance, which means it’s available without a prescription, and it’s not illegal to possess it, sell it or use it, at least not in the United States.

Phenibut’s powder use stems back to the 1960s, where it was used in Russia as an anti-anxiety medicine.

Phenibut acts as a central nervous system depressant, and it has both relaxing and euphoric effects for users. It’s similar in structure to a neurotransmitter called GABA, which has a calming effect on the neuron activity in the brain. Unlike the supplement GABA, phenibut does have the ability to cross the blood-brain barrier, so it has psychoactive effects. Specific things phenibut is often used to treat include anxiety, depression, PTSD, insomnia, and alcoholism. It’s also sometimes used by people who are going through withdrawal from drugs or alcohol.

Phenibut has sedative effects, and it’s also been shown to increase dopamine levels in the brain, which is why some people may find that it has euphoric effects.