This is an unofficial archive of PsychonautWiki as of 2025-08-08T03:33:20Z. Content on this page may be outdated, incomplete, or inaccurate. Please refer to the original page for the most up-to-date information.
WARNING: Always start with lower doses due to differences between individual body weight, tolerance, metabolism, and personal sensitivity. See responsible use section.
DISCLAIMER: PW's dosage information is gathered from users and resources for educational purposes only. It is not a recommendation and should be verified with other sources for accuracy.
Phenibut is a closely related structural analog of the naturally occurring inhibitory neurotransmitter gamma-aminobutyric acid (GABA). The addition of a phenyl ring to GABA allows it to cross the blood-brain barrier and produce psychoactive effects, a notable difference from GABA when taken exogenously.[4] It is also structurally related to baclofen, pregabalin, and GABOB.[4]
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 post-traumatic stress disorder, anxiety, depression, asthenia, insomnia, alcoholism, stuttering, and vestibular disorders, and other conditions.[5][6][4]
In the rest of the world, phenibut is not approved for clinical use and is instead sold as a nutritional supplement. It has been reported by some researchers to possess nootropic actions for its ability to improve neurological functions,[5] but others have not observed these effects.[7] It is generally accepted that phenibut has anxiolytic effects in both animal models and in humans.[4]
Phenibut is a derivative of GABA with a phenyl group in the β-position. It is a chiral molecule and thus has two potential configurations, as (R)- and (S)-enantiomers.[8] It has almost the same structure of baclofen (lacking only a chlorine atom in the para-position of the phenyl group)[9] and contains phenethylamine in its structure.[10]Pregabalin has the same structure as phenibut, except that the phenyl group is instead an isobutyl group.
Most commercial phenibut is in the form of the hydrochloride salt (HCl). In this form, the phenibut is reacted with hydrochloric acid to form a stable, easily dissolvable, acidic, crystalline salt.
Alternatively, phenibut can exist as a Free Amino Acid (FAA). In this form, phenibut is close to pH neutral, non-crystalline, slow to dissolve and mildly bitter. The FAA form has about 20% more phenibut molecules on an equal mass basis compared to phenibut HCl. Phenibut FAA has the advantage of being suitable for sublingual, rectal, or intranasal use, which can be more efficient, faster acting, and predictable for some. Phenibut FAA is converted to phenibut HCl in the stomach. Equal masses of the two forms will have roughly equivalent effects when taken the same way (FAA may be slightly stronger).
Pharmacology
Phenibut is substantially more complex in its pharmacological profile than most other depressants. Unlike most depressants such as benzodiazepines, phenibut acts as a full agonist of the GABABreceptor, similar to baclofen and high doses of GHB.[11] At higher doses, phenibut loses its selectivity of GABAB, and acts as a GABAAagonist as well.[5] Phenibut's effects at the GABAB receptor are responsible for its sedating effects.
Recent research has shown that phenibut binds to and blocks α2δ subunit-containing voltage-dependent calcium channels (VDCCs), similarly to gabapentinoids such as gabapentin
and pregabalin.[12] Both enantiomers of phenibut show this action with similar efficacy. The R-enantiomer possesses five-fold greater affinity for
α2δ subunit-containing voltage-gated calcium channels relative to the GABAB receptor, whereas the S-entantiomer does not have any efficacy at the GABAB receptor.[12]
The analgesic effects of phenibut in rodents are not mediated by the GABAB receptor but by the blockage of α2δ subunit-containing voltage-gated calcium channels.[12]
Additionally, phenibut has been found to increase dopamine levels within the brain. It is not known how this contributes to its effects[4].
Subjective effects
Disclaimer: The effects listed below cite the Subjective Effect Index (SEI), an open research literature based on anecdotal user reports and the personal analyses of PsychonautWikicontributors. As a result, they should be viewed with a healthy degree of skepticism.
It is also worth noting that these effects will not necessarily occur in a predictable or reliable manner, although higher doses are more liable to induce the full spectrum of effects. Likewise, adverse effects become increasingly likely with higher doses and may include addiction, severe injury, or death ☠.
In comparison to other commonly used GABAergic depressants such as alcohol or benzodiazepines, this compound is reported to be longer lasting, more euphoric and more recreational at higher doses.
Physical effects
Stimulation and Sedation - At lower doses, phenibut has a mild physical and mental stimulation effect, encouraging movement, wakefulness, and productivity. At higher doses, however, it becomes physically sedating, encouraging sleep and lethargy. Sleeping after dosing a small amount results in a deep, restful sleep which can leave the user feeling refreshed and alert upon waking.
Nausea - Phenibut can induce mild to extreme nausea depending greatly on dose and tolerance. It usually manifests roughly 5 hours after the initial dose and generally involves waves of nausea accompanied by vomiting and excessive sweating.
Orgasm suppression - At higher doses, rather than reducing sensitivity, phenibut has a propensity to cause spontaneous motor control loss when nearing orgasm.
Internal hallucinations - One may experience a state of semi-consciousness and hypnagogia during heavy dosage nodding which results in dream-like states and up to level 3 imagery. This is often accompanied by ill-defined geometry.
Empathy, affection, and sociability enhancement - Phenibut has been reported to produce strong prosocial and entactogenic effects which, although much weaker than that of traditional entactogens such as MDMA, are prominent and well-defined even at common doses.
Analysis suppression - High doses will usually induce a state of mild stupor and confusion.
Rebound anxiety - Rebound anxiety is a commonly observed effect with anxiolytic substances like phenibut. It typically corresponds to the total duration spent under the substance's influence along with the total amount consumed in a given period, an effect which can easily lend itself to cycles of dependence and addiction.
Residual sleepiness - While phenibut can be used as an effective sleep-inducing aid, their effects may persist into the morning afterward, which may lead users to feel "groggy" or "dull" for up to a few hours if not longer.
Depression - A low mood can be experienced as an after-effect of high or frequent dosing.
Experience reports
There are currently no anecdotal reports which describe the effects of this compound within our experience index. Additional experience reports can be found here:
Phenibut hydrochloride is highly caustic and in many sensitive users can cause intestinal discomfort and diarrhea with some lower digestive tract bleeding. The digestive issues can present themselves within an hour of dosing, or not occur until the next morning. This compound should therefore be taken on an empty stomach as the ionization state of the compound dictates its absorption. After dosing there will be an acute rise in stomach acidity and high doses can cause acid reflux, vomiting, and nausea.
Due to the extremely long come up of phenibut in comparison to other drugs, some users may have an urge to redose as they believe it is not working. This should be avoided to prevent overdose of the drug.
Phenibut is moderately physically and psychologically addictive, although this usually only occurs with heavy abuse of the substance.
Tolerance will develop to the sedative-hypnotic effects within a couple of days of continuous use. After cessation, the tolerance returns to baseline in 7 - 14 days. Withdrawal symptoms or rebound symptoms may occur after ceasing usage abruptly following a few weeks or longer of steady dosing and may necessitate a gradual dose reduction.
Phenibut presents cross-tolerance with [[Cross-tolerance::all GABAgenic depressants]], meaning that after its consumption, most depressants will have a reduced effect.
Dangerous interactions
Although many drugs are safe on their own, they can become dangerous and even life-threatening when combined with other substances. The list below contains some common potentially dangerous combinations, but may not include all of them. Certain combinations may be safe in low doses of each but still increase the potential risk of death. Independent research should always be done to ensure that a combination of two or more substances is safe before consumption.
Dissociatives - This combination can result in an increased risk of vomiting during unconsciousness and dying from the resulting suffocation. If a sudden loss of consciousness occurs, users should attempt to fall asleep in the recovery position or have a friend move them into it.
Stimulants - It is dangerous to combine phenibut with stimulants due to the risk of excessive intoxication. Stimulants mask the sedative effect of phenibut, which is the main factor most people consider when determining their level of intoxication. Once the stimulant wears off, the effects of phenibut will be significantly increased, leading to intensified disinhibition as well as other effects. If combined, one should strictly limit themselves to only dosing a certain amount of phenibut per hour. This combination can also potentially result in severe dehydration if hydration is not monitored.
As such, it may contain incomplete or wrong information. You can help by expanding it.
United States - Phenibut is uncontrolled, meaning it is legal to possess without any sort of license or prescription.[14]
United Kingdom - Phenibut is uncontrolled and is legal to possess. It may be illegal to produce, supply, or import this drug under the Psychoactive Substance Act 2016, which blanketly applies the aforementioned restrictions on all "psychoactive substances" with exemptions for alcohol, nicotine and "medicinal products".[15]
↑ 5.05.15.2Shulgina, G. I. (1986). "On neurotransmitter mechanisms of reinforcement and internal inhibition". The Pavlovian journal of biological science (PubMed.gov / NCBI) | https://www.ncbi.nlm.nih.gov/pubmed/2431377
↑Kovaleva, E. L. (1984). "Comparative characteristics of the nootropic action of fenibut and fepiron". Farmakologiia i toksikologiia (PubMed.gov / NCBI) | https://www.ncbi.nlm.nih.gov/pubmed/6705902
↑Dambrova, M., Zvejniece, L., Liepinsh, E., Cirule, H., Zharkova, O., Veinberg, G., & Kalvinsh, I. (2008). Comparative pharmacological activity of optical isomers of phenibut. European journal of pharmacology, 583(1), 128-134.
↑Shulgina, G. I. (1986). On neurotransmitter mechanisms of reinforcement and internal inhibition. Integrative Physiological and Behavioral Science, 21(4), 129-140.
↑ 12.012.112.2Dambrova, M.; Zvejniece, L.; Liepinsh, E.; Cirule, H.; Zharkova, O.; Veinberg, G.; Kalvinsh, I. (2008). "Comparative pharmacological activity of optical isomers of phenibut". European Journal of Pharmacology (PubMed.gov / NCBI) | https://www.ncbi.nlm.nih.gov/pubmed/18275958
↑Koski, A., Ojanperä, I., & Vuori, E. (2002). Alcohol and benzodiazepines in fatal poisonings. Alcoholism: Clinical and Experimental Research, 26(7), 956-959.
