Fatal overdose may occur when gabapentinoids are combined with other depressants such as opiates, benzodiazepines, barbiturates, thienodiazepines, alcohol or other GABAergic substances.
It is strongly discouraged to combine these substances, particularly in common to heavy doses.
|Summary sheet: Phenibut|
|Common names||Phenibut, Fenibut, Phenybut, PhGABA|
|Substitutive name||β-Phenyl-γ-aminobutyric acid|
|Systematic name||(RS)-4-Amino-3-phenyl-butyric acid|
|Routes of Administration|
β-Phenyl-γ-aminobutyric acid (also known as Fenibut, Phenybut, Noofen, Citrocard, and commonly as Phenibut) is a lesser-known depressant substance of the gabapentinoid class. Phenibut acts as a receptor agonist for GABA, the major inhibitory neurotransmitter in the brain. It is chemically related to baclofen, pregabalin, and gabapentin.
Phenibut was developed in the Soviet Union in the 1960s, where it has been used as a pharmaceutical drug to treat a wide variety of conditions, including post-traumatic stress disorder, anxiety, depression, asthenia, insomnia, alcoholism, stuttering, and vestibular disorders, and others. In the rest of the world, phenibut is not approved for clinical use and is instead sold as a nutritional supplement.
Subjective effects include anxiety suppression, sedation, muscle relaxation, enhanced motivation, and euphoria. Lower doses (under 1 gram) are typically used as a cognitive and lifestyle supplement while higher doses are used for a recreational high that is reported to be subjectively similar to GHB, alcohol, and certain benzodiazepines.
Although phenibut is commonly marketed as a nootropic by retailers, evidence that it enhances cognition is limited. It is generally accepted that phenibut has anxiolytic effects in both animal and in humans. Due to its habit-forming properties, it is highly advised to use harm reduction practices if using this substance.
Phenibut is a derivative of GABA with a phenyl group in the β-position. The addition of a phenyl ring to the GABA molecule allows it to cross the blood-brain barrier and produce psychoactive effects. Phenibut has a near-identical structure as baclofen, lacking only a chlorine atom in the para-position of the phenyl group and contains phenethylamine in its structure. Pregabalin also has a near-identical structure as phenibut, except it has an isobutyl group instead of a phenyl group.
Phenibut is a chiral molecule and thus has two potential configurations, as (R)- and (S)-enantiomers.
Most commercial phenibut is reported to be 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).
Phenibut has a more complex pharmacological profile than many other depressants. Unlike benzodiazepines, for example, phenibut acts as a full agonist of the GABAB receptor, similar to baclofen and high doses of GHB. At higher doses, phenibut loses its selectivity of GABAB, and gains additional activity as a GABAA agonist. 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. 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.
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.
In comparison to other commonly used GABAergic depressants such as alcohol or benzodiazepines, phenibut is reported to be longer-lasting, more euphoric and more recreational at higher doses.
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 PsychonautWiki contributors. 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 ☠.
- Sedation or Stimulation - Phenibut has different effects on physical energy levels depending on the dosage used. At lower doses, phenibut has a mild physical and mental stimulation effect, encouraging movement, wakefulness, and productivity. At common doses and higher, phenibut is 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.
- Physical euphoria
- Muscle relaxation
- Respiratory depression - This effect is generally mild compared to that experienced on many other depressants. However, it may become dangerously amplified if phenibut is combined with other substances that depress breathing.
- Nausea - Phenibut can induce mild to extreme nausea depending greatly on dose and tolerance. When it occurs, it usually manifests roughly 5 hours after the initial dose and generally involves waves of nausea accompanied by vomiting and excessive sweating.
- Increased libido - Phenibut is reported to enhance sexual desire and energy. Combined with its disinhibiting and euphoric effects, it can increase the likelihood of unplanned sexual activities in a manner similar to alcohol.
- Orgasm suppression - At higher doses, rather than reducing sensitivity, phenibut has a propensity to cause spontaneous motor control loss when nearing orgasm.
- Pain relief
- Increased perspiration
- Motor control loss
- Stomach cramps- This effect is more commonly reported with the hydrochloric acid form (phenibut HCl).
- Diarrhea - This effect is uncommon, and mostly occurs on higher doses.
- Headaches - Moderate to high doses can induce a mild headache many hours after dosing.
- Muscle cramps - Muscle cramps and joint pain are sometimes accompanied at high doses.
- Difficulty urinating - This effect generally only occurs after frequent usage.
- Increased blood pressure
- Temperature regulation suppression
- Pupil dilation - This effect is common at high doses.
- Appetite enhancement - This effect is uncommon and inconsistently produced.
- Internal hallucination - One may experience a state of semi-consciousness and hypnagogia during heavy dose "nodding" which results in dream-like states and up to level 3 imagery. This may be accompanied by ill-defined geometry.
- Anxiety suppression - Phenibut has medium to strong anxiolytic effects, equivalent to alcohol but generally less powerful than benzodiazepines.
- Disinhibition - Phenibut has strong disinhibiting effects comparable to that of higher doses of alcohol, benzodiazepines, or GHB.
- Cognitive euphoria - This effect is more pronounced than that of alcohol and benzodiazepines, most likely due to more clear-headed and stimulative nature of phenibut.
- Empathy, affection, and sociability enhancement - Phenibut has been reported to produce prosocial and mild entactogenic effects which, although much weaker than that of traditional entactogens such as MDMA, are prominent and well-defined even at common doses.
- Motivation enhancement
- Focus enhancement - Lower doses of phenibut can enhance focus and concentration. This effect typically reverses as the dose is increased.
- Analysis suppression - High doses will usually induce a state of mild stupor and confusion.
- Thought deceleration
- Increased music appreciation
- Compulsive redosing
- 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.
- Depersonalization - Feelings of mild to strong depersonalization may present themselves after phenibut usage, particularly when it is taken frequently at higher doses.
- Dream potentiation - This is caused by phenibut's REM sleep suppressing activity, resulting in REM rebound upon cessation of dosing.
There are currently 2 experience reports which describe the effects of this compound in our experience index.
Additional experience reports can be found here:
Toxicity and harm potential
This toxicity and harm potential section is a stub.
As a result, it may contain incomplete or even dangerously wrong information! You can help by expanding upon or correcting it.
Phenibut has a low toxicity relative to dose. However, it is potentially lethal when mixed with depressants like alcohol, benzodiazepines or opioids.
Phenibut hydrochloride is highly caustic and in sensitive users can cause intestinal discomfort and diarrhea with some lower digestive tract bleeding.
Due to the extremely long come up period relative to other substances, some users may experience an urge to redose out of the belief that it is weak or not working. This should be avoided to prevent overdose.
It is strongly recommended that one use harm reduction practices when using this substance.
Dependence and abuse potential
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. Withdrawal symptoms include severe anxiety, nervousness, hallucinations, tremors, agitation, dizziness, tension, irritation, rapid heartbeat, fatigue, loss of appetite, nausea, vomiting, psychosis, and insomnia.
Phenibut produces cross-tolerance with all GABAgenic depressants, meaning that after its consumption, depressants will have a reduced effect.
Warning: Many psychoactive substances that are reasonably safe to use on their own can suddenly become dangerous and even life-threatening when combined with certain other substances. The following list provides some known dangerous interactions (although it is not guaranteed to include all of them).
Always conduct independent research (e.g. Google, DuckDuckGo, PubMed) to ensure that a combination of two or more substances is safe to consume. Some of the listed interactions have been sourced from TripSit.
- Depressants (1,4-Butanediol, 2M2B, alcohol, benzodiazepines, barbiturates, GHB/GBL, methaqualone, opioids) - This combination can result in dangerous or even fatal levels of respiratory depression. These substances potentiate the muscle relaxation, sedation and amnesia caused by one another and can lead to unexpected loss of consciousness at high doses. There is also an increased risk of vomiting during unconsciousness and death from the resulting suffocation. If this occurs, users should attempt to fall asleep in the recovery position or have a friend move them into it.
- Dissociatives - This combination can result in an increased risk of vomiting during unconsciousness and death 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 - Phenibut is reported to enhance the positive effects of stimulants as well as reduce jitteriness and anxiety. However, this combination can be dangerous due to the risk of excessive intoxication. Stimulants mask the sedative effects of phenibut; once the stimulant wears off, the depressant effects of phenibut will be significantly increased, leading to intensified disinhibition as well as other effects. If combined, one should strictly limit themselves to a certain dose of phenibut prior to stimulant consumption and not redose. This combination can also potentially result in significant dehydration.
- Australia: Phenibut is a schedule 9 substance in Australia as of February 1st 2018, meaning it is illegal to possess, import, supply or manufacture.
- Canada: Phenibut is not a controlled substance in Canada, meaning it is legal to possess without any sort of license or prescription.
- Germany: Phenibut may be controlled under the NpSG (New Psychoactive Substances Act) as of July 18, 2019.  If this law applies to Phenibut remains unclear.
- Switzerland: Phenibut is not controlled under Buchstabe A, B, C and D. It could be considered legal.
- United Kingdom: Phenibut is not a controlled substance in the United Kingdom. It may be illegal to produce, supply, or import this drug under the Psychoactive Substance Act 2016, which applies a blanket restriction on all "psychoactive substances" with exemptions for alcohol, nicotine and "medicinal products".
- United States: Phenibut is not a controlled substance in the United States, meaning it is federally legal to possess without any sort of license or prescription.Phenibut is a Schedule II controlled substance in Alabama as of November 21st, 2021.
- Italy: Phenibut is a Schedule 1 controlled substance.
- ↑ Risks of Combining Depressants - TripSit
- ↑ Wyllie, E., Cascino, G. D., Gidal, B. E., Goodkin, H. P. (17 February 2012). Wyllie’s Treatment of Epilepsy: Principles and Practice. Lippincott Williams & Wilkins. ISBN 9781451153484.
- ↑ Benzon, H., Rathmell, J. P., Wu, C. L., Turk, D., Argoff, C. E., Hurley, R. W. (11 September 2013). Practical Management of Pain E-Book. Elsevier Health Sciences. ISBN 9780323170802.
- ↑ 4.0 4.1 4.2 4.3 Lapin, I. (7 June 2006). "Phenibut (β-Phenyl-GABA): A Tranquilizer and Nootropic Drug". CNS Drug Reviews. 7 (4): 471–481. doi:10.1111/j.1527-3458.2001.tb00211.x. ISSN 1080-563X.
- ↑ Shulgina, G. I. (December 1986). "On neurotransmitter mechanisms of reinforcement and internal inhibition". The Pavlovian Journal of Biological Science. 21 (4): 129–140. doi:10.1007/BF02734511. ISSN 0093-2213.
- ↑ 6.0 6.1 Group, D. W. (25 February 2015). Encyclopedia of Mind Enhancing Foods, Drugs and Nutritional Substances, 2d ed. McFarland. ISBN 9780786441426.
- ↑ Shulgina, G. I. (October 1986). "On neurotransmitter mechanisms of reinforcement and internal inhibition". The Pavlovian Journal of Biological Science. 21 (4): 129–140. doi:10.1007/BF02734511. ISSN 0093-2213.
- ↑ Lapin, I. (2001). "Phenibut (beta-phenyl-GABA): a tranquilizer and nootropic drug". CNS drug reviews. 7 (4): 471–481. doi:10.1111/j.1527-3458.2001.tb00211.x. ISSN 1080-563X.
- ↑ Dambrova, M., Zvejniece, L., Liepinsh, E., Cirule, H., Zharkova, O., Veinberg, G., Kalvinsh, I. (March 2008). "Comparative pharmacological activity of optical isomers of phenibut". European Journal of Pharmacology. 583 (1): 128–134. doi:10.1016/j.ejphar.2008.01.015. ISSN 0014-2999.
- ↑ GABAb Receptor Pharmacology: A Tribute to Norman Bowery. Academic Press. 21 September 2010. ISBN 9780123786487.
- ↑ Zyablitseva, E. A.; Pavlova, I. V. (2010). "Effects of the GABA Receptor Agonist Phenibut on Spike Activity and Interactions between Neocortex and Hippocampus Neurons in Emotionally Negative Situations". Neuroscience and Behavioral Physiology. 40 (9): 1003–1011. doi:10.1007/s11055-010-9360-y. ISSN 0097-0549.
- ↑ 12.0 12.1 12.2 Dambrova, M., Zvejniece, L., Liepinsh, E., Cirule, H., Zharkova, O., Veinberg, G., Kalvinsh, I. (31 March 2008). "Comparative pharmacological activity of optical isomers of phenibut". European Journal of Pharmacology. 583 (1): 128–134. doi:10.1016/j.ejphar.2008.01.015. ISSN 0014-2999.
- ↑ Koski, A., Ojanpera, I., Vuori, E. (July 2002). "Alcohol and Benzodiazepines in Fatal Poisonings". Alcoholism: Clinical and Experimental Research. 26 (7): 956–959. doi:10.1111/j.1530-0277.2002.tb02627.x. ISSN 0145-6008.
- ↑ The Drug Classroom - Phenibut: Combinations
- ↑ "Anlage NpSG" (in German). Bundesministerium der Justiz und für Verbraucherschutz. Retrieved December 10, 2019.
- ↑ "Verordnung zur Änderung der Anlage des Neue-psychoaktive-Stoffe-Gesetzes und von Anlagen des Betäubungsmittelgesetzes" (PDF). Bundesgesetzblatt Jahrgang 2019 Teil I (in German). Bundesanzeiger Verlag. July 17, 2019. Retrieved December 28, 2019.
- ↑ "§ 4 NpSG" (in German). Bundesministerium der Justiz und für Verbraucherschutz. Retrieved December 10, 2019.
- ↑ Evaluation der Auswirkungen des Neue-psychoaktive-Stoffe-Gesetzes (NpSG): Abschlussbericht.
- ↑ "Verordnung des EDI über die Verzeichnisse der Betäubungsmittel, psychotropen Stoffe, Vorläuferstoffe und Hilfschemikalien" (in German). Bundeskanzlei [Federal Chancellery of Switzerland]. Retrieved January 1, 2020.
- ↑ Psychoactive Substances Act 2016
- ↑ Erowid Phenibut Vault: Legal Status
- ↑ Alabama List of Controlled Substanceshttps://www.alabamapublichealth.gov/blog/assets/controlledsubstanceslist.pdf
- ↑ Tabella 1(PDF) (in Italian). Ministero della Salute [Ministry of Health]. p.19. Retrieved November 24, 2020.