Phenibut (contracted from β-phenyl-γ-aminobutyric acid) is a central nervous system (CNS) depressant and derivative of the naturally occurring inhibitory neurotransmitter γ-aminobutyric acid (GABA). The addition of a phenyl ring allows phenibut to cross the bloodâ€"brain barrier. Phenibut is sold as a nutritional supplement, and is not approved as a pharmaceutical in the United States or Europe, but in Russia it is sold as a psychotropic drug. It has been reported by some to possess nootropic actions for its ability to improve neurological functions, but other researchers have not observed these effects. It is generally accepted that phenibut has anxiolytic effects in both animal models and in humans. Phenibut was discovered in the Soviet Union in the 1960s, and has since been used there to treat a wide range of ailments including posttraumatic stress disorder, anxiety, and insomnia.
The name phenibut, along with many of the other names for the compound, comes directly from the chemical name for the compound, β-phenyl-γ-aminobutyric acid.
History
Phenibut was synthesized at the A. I. Herzen Leningrad Pedagogical Institute (USSR) by Professor V. V. Perekalin's team and tested at the Institute of Experimental Medicine, Academy of Medical Sciences USSR.
Phenibut is mandated standard equipment in a Russian cosmonaut's medical kit. The use of "conventional" tranquilizers for stress and anxiety makes patients drowsy, which was deemed unacceptable for cosmonauts; phenibut, however, lowers stress levels without adversely affecting performance. In 1975 phenibut was included in the cosmonauts' kit for those who participated in the Apollo-Soyuz joint mission.
General information
In chemical structure, phenibut is a phenyl derivative of GABA. Although the calming action is similar to other GABA agonists, phenibut binds to the GABAB metabotropic receptor, the same site responsible for the sedative effects of baclofen (the para-chloro derivative of phenibut) and γ-hydroxybutyrate (GHB), although GHB also acts at the GHB receptor. There is dispute in the literature about whether or not phenibut binds to the GABAA ionotropic receptor, which is responsible for the actions of the benzodiazepines, barbiturates, Z-drugs, and for some of the effects of ethanol. According to Allikmets and Ryage (1983) and Shulgina (1986) phenibut does bind to the GABAA receptor, but according to Lapin (2001) it does not. In the case of the former, it is argued that the GABAA binding only occurs at higher concentrations.
The literature that supports the nootropic effects of phenibut also suggest it elicits tranquilizing effects, reduction of stress and anxiety, improvement of impaired sleep, and the potentiation of the effects of tranquilizers, narcotics, and neuroleptics. It is also suggested to have an anticonvulsant effect, though studies on other GABAB agonists, such as GHB and the phenibut analogue baclofen, have shown them to act as potential convulsants. It should be noted, however, that GHB acts on the convulsion-inducing GHB receptor, which phenibut does not.
Physical properties
Phenibut HCl is a white crystalline powder and the taste is very sour. It is readily soluble in water, soluble in alcohol, and the pH of a 2.5% water solution is between about 2.3 and 2.7.
Chemistry
Phenibut is a γ-aminobutyric acid with a phenyl group in the β-position. It is a chiral molecule and thus has two potential configurations, an (R)- and (S)-enantiomer. In phenibut, only the (R)-enantiomer is biologically active leaving the (S)-enantiomer of little value. It has the same structure of baclofen (lacking only a chlorine atom in the para-position of the phenyl group) and includes the phenylethylamine structure.
Pregabalin has instead the phenyl group substituted with the isobutyl group.
Pharmacology
The pharmacological effects of phenibut are similar to baclofen, but less potent per milligram of dosage.
Phenibut exerts its effects by being an agonist at the metabotropic GABAB receptor, and at higher doses also at the ionotropic GABAA receptor.
Some studies found that phenibut antagonizes the effects of phenethylamine (PEA), while others found no effect on PEA-induced anxiety.
Furthermore, phenibut has been shown to increase dopamine levels.
Contraindications and side effects
Persons on MAO inhibitors or epilepsy medications like carbamazepine or oxcarbazepine should consult with their physician or pharmacist prior to supplementation with phenibut. Some evidence suggests that phenibut can modulate the function of some epilepsy medications.
See also
- Baclofen
- Gabapentin
- Pregabalin
References
Notes
External links
- 4-Amino-3-phenylbutyric acid in the ChemIDplus database