Phenibut (contracted from β-phenyl-γ-aminobutyric acid) is a central nervous system (CNS) depressantand derivative of the naturally occurring inhibitory neurotransmitter γ-aminobutyric acid (GABA).

1.Phenibut is a derivative of the naturally occurring inhibitory neurotransmitter GABA.
2.Phenibut is used by bodybuilders to reduce fatigue and improve neurological functions.
3.Phenibut has been and is still used medically to treat stress,relieve tension, improve sleep,and as a potentiate for other medications.

Phenibut is a central depressant and analog of the inhibitory neurotransmitter γ-aminobutyric acid (GABA), or a GABA analogue. The addition of a phenyl ring allows phenibut to cross the blood-brain barrier. Phenibut was developed in the Soviet Union in the 1960s, and has since been used there as a pharmaceutical drug to treat a wide range of ailments, including posttraumatic stress disorder, anxiety, depression, asthenia, insomnia, alcoholism, stuttering, and vestibular disorders, and other conditions.
Phenibut is a close structural analogue of GABA, as well as of baclofen (β-(4-chlorophenyl)-GABA), (β-isobutyl-GABA), and GABOB (β-hydroxy-GABA). Phenibut is believed to act as a selective GABAB receptor agonist; studies are conflicting as to whether phenibut also acts as a GABAA receptor agonist. More recently, phenibut has been found to act preferentially as a blocker of α2δ subunit-containing voltage-gated calcium channels, similarly to gabapentin. As such, by definition, phenibut is a gabapentinoid.