Not yet reviewed — this article is pending editorial review by Lyrea.

Phenibut

beta-phenyl-gamma-aminobutyric acid

Fenibut, Phenybut, PhGABA, Noofen, Anvifen

Psychoactive Class

Depressant Anxiolytic GABAergic

Chemical Class

GABA analogue Gabapentinoid

Phenibut is a depressant and anxiolytic of the gabapentinoid class, structurally derived from the neurotransmitter GABA. Developed in the Soviet Union during the 1960s under Professor V. V. Perekalin, it remains a prescribed pharmaceutical in Russia for conditions including anxiety, insomnia, depression, and PTSD. Outside Russia, it is unapproved for clinical use and typically sold as a nutritional supplement.¹² At common doses, it is noted for producing less drowsiness than other GABAergic substances such as benzodiazepines.

Dosage & Duration

Dosage

Threshold~0.25 g

Light0.5-1 g

Moderate1-2 g

Strong2-3.5 g

Heavy3.5+ g

The onset of effects is considerably slower than most other central nervous system depressants. To reduce the risk of accidental overdose, a minimum interval of two to three hours should be observed before considering any additional dose.

Duration

Onset1.5-3 hours

Come Up1.5-3 hours

Peak3-4 hours

Offset4-6 hours

After Effects6-24 hours

Total10-16 hours

Half-life

~5.3 hours

Subjective Effects

In comparison to other commonly used GABAgenic depressants such as alcohol or benzodiazepines, this compound is significantly longer lasting, more euphoric and more recreational.

Physical

Respiratory depressionIncreased perspiration Motor control loss Stomach cramps DizzinessPhysical euphoriaIncreased blood pressure Temperature regulation loss Appetite enhancement

Cognitive

DisinhibitionThought deceleration Cognitive euphoria Motivation enhancement Anxiety suppressionAmnesia

Forked from Subjective Effect Documentation

by Josie KinsJuly 2016.

Reagent Testing

Expected colorimetric results for common reagent tests. Colors show reaction change over 1–2 minutes.

Mandelin(MD)

Liebermann(LB)

Marquis(MQ)

No reaction

Mecke(ME)

No reaction

PROtestkit.eu

Pharmacology

Pharmacodynamics

Phenibut acts as a full agonist of the GABA-B receptor and as a blocker of α2δ subunit-containing voltage-dependent calcium channels (VDCCs), the latter mechanism being shared with gabapentinoids such as gabapentin and pregabalin.³ Phenibut's affinity for α2δ-containing VDCCs is higher than for the GABA-B receptor, and in rodent models, analgesic effects appear mediated by VDCC blockade rather than GABA-B agonism.³ Only (R)-phenibut has meaningful activity at GABA-B, while both enantiomers block VDCCs with similar potency.⁴³ At higher doses, phenibut loses its GABA-B selectivity and gains additional activity as a GABA-A receptor agonist.⁵ Phenibut has also been reported to increase calcium-dependent spontaneous release of GABA in vitro, and its effects on dopamine remain unclear, with conflicting reports regarding whether it meaningfully raises dopamine levels.⁶⁵

Pharmacokinetics

Phenibut is not significantly metabolized and is largely excreted unchanged in the urine, with approximately 63-65% of the dose recovered renally.⁷ Following a single 250 mg oral dose in healthy volunteers, the elimination half-life was approximately 5.3 hours.⁷

Metabolitesnone documented yet

Interactions

Dangerous

Highest risk

These combinations are considered extremely harmful and should always be avoided. Reactions to these drugs taken in combination are highly unpredictable and have a potential to cause death.

DissociativesStimulants

TripSit

Tolerance

Full Tolerance

Tolerance to the sedative-hypnotic effects develops rapidly, typically within a couple of days of continuous use. Some users report noticeable tolerance after a single week of daily dosing. The Russian clinical literature indicates the substance is intended for only a few weeks of continuous use at the same dose due to this rapid tolerance development. Notably, tolerance to different effects may develop at different rates—sedative effects diminish while nootropic effects may be preserved or even enhanced with chronic dosing.

Baseline Reset

Full baseline tolerance is typically restored within 7-14 days of abstinence. Neuroadaptive changes to GABA receptor systems, including downregulation of GABA-B receptors and alterations in benzodiazepine and GABA-A receptor binding, have been observed to normalize within 24-48 hours after cessation in animal studies, though complete functional recovery in humans may take longer.

Half Tolerance

Tolerance begins to decrease after cessation, though specific half-tolerance timelines are not well-established in the literature.

Cross Tolerance

GABAergic depressants (benzodiazepines, alcohol, GHB), Other GABA-B agonists (baclofen)

Harm Potential

Addiction & Dependence

Psychological

Moderate

Phenibut is moderately psychologically addictive, particularly with heavy or frequent use.⁸ The extended onset period can lead to compulsive redosing when users mistakenly believe the substance is not working, and rebound anxiety commonly drives continued use.⁹

Physical

Moderate

Physical dependence develops with daily or near-daily use, sometimes within weeks of regular dosing.¹⁰¹¹ Withdrawal symptoms can be severe and include anxiety, insomnia, tremors, agitation, rapid heartbeat, nausea, vomiting, irritability, and fatigue.¹⁰¹ Baclofen has been used successfully to treat phenibut dependence.¹¹²

Toxicity

Hepatic

Prolonged use at high doses may cause fatty liver disease; doses above 7 grams have been associated with fatty liver degeneration in overdose cases.¹³

Renal

Renal impairment has been reported in overdose cases; this is not a typical concern at standard doses.¹⁰

Gastrointestinal

Phenibut hydrochloride is highly caustic and may cause intestinal discomfort, diarrhea, and potentially lower digestive tract bleeding in sensitive users.

Hematological

Eosinophilia has been reported with prolonged high-dose use and in overdose cases.¹⁰

Psychosis Risk

Acute psychosis and visual/auditory hallucinations have been reported primarily as withdrawal symptoms in recreational users discontinuing heavy use, rather than during intoxication.¹⁴ Withdrawal-associated psychosis appears to occur in cases of abrupt cessation following prolonged high-dose use.¹⁰¹

Seizure Risk

Tonic-clonic seizures have been reported in recreational users who have overdosed.¹⁵ Seizures are not a typical occurrence at standard doses and appear to be associated with significant overdose.¹⁰

History & Culture

Development and Soviet Adoption

Phenibut was synthesized during the 1960s at the Department of Organic Chemistry at the Al Gertsen Leningrad Pedagogical Institute under the supervision of Professor V. V. Perekalin.⁵ Following its development, the compound was researched for potential…

Legality

International

Phenibut is not internationally scheduled under the 1961 Single Convention, the 1971 Convention on Psychotropic Substances, or the 1988 Convention against Illicit Traffic. The official convention schedules and INCB consolidated narcotic and psychotropic lists do not name phenibut, fenibut, or 4-amino-3-phenylbutanoic acid.

By Country

United StatesRestrictedSection 301(a)

Federal Food, Drug, and Cosmetic Act^56575859

Not a federally scheduled substance. Legal to possess without license or prescription. Sales, distribution, and labeling are regulated by FDA rules when sold for human consumption.⁶⁰ Note that Alabama classified phenibut as a Schedule II controlled substance at the state level as of November 21st, 2021.⁶¹

By state

Across the 50 states, D.C., and the permanent territories, most jurisdictions treat Phenibut consistently with federal control; listed entries record independently verified differences in state classification or coverage.

IowaNot scheduledUnscheduled

KentuckyNot scheduledUnscheduled

MaineNot scheduledUnscheduled

MassachusettsNot scheduledUnscheduled

MichiganNot scheduledUnscheduled

MinnesotaNot scheduledUnscheduled

MissouriNot scheduledUnscheduled

NebraskaNot scheduledUnscheduled

NevadaNot scheduledUnscheduled

South DakotaIllegalSchedule I controlled substance

AustraliaIllegalSchedule 9

Poisons Standard June 2018²¹²²

Classified as a prohibited substance as of February 1st, 2018.²³ Possession, importation, supply, and manufacture are illegal.

FranceIllegalListe des substances psychotropes

Arrêté du 9 septembre 2020 modifiant l'arrêté du 22 février 1990 fixant la liste des substances psychotropes^24252627

Phenibut (acide 4-amino-3-phénylbutanoïque) is listed in France's list of psychotropic substances from 12 September 2020. Its production, manufacture, transport, import, export, possession, offer, transfer, acquisition, and use are prohibited unless expressly authorised under Article R. 5132-88 of the Code de la santé publique.

ItalyIllegalTabella I

Decreto del Ministro della salute, 11 agosto 2020³²³³

Classified as a Schedule 1 controlled substance.³² Possession, production, and distribution are prohibited.

NetherlandsIllegal (analog/blanket ban)Lijst IA

Opiumwet³⁶³⁷

Phenibut is prohibited in the Netherlands as a substance derived from 2-phenethylamine under List IA of the Opium Act. The generic List IA prohibition has applied since 1 July 2025 and prohibits importing, exporting, preparing, processing, selling, supplying, transporting, possessing, and manufacturing substances in its listed structural groups. Phenibut’s 4-amino-3-phenylbutanoic-acid structure is a substituted 2-phenethylamine within that statutory group.

NorwayIllegalNarkotikalisten

Forskrift om narkotika (narkotikaforskriften), FOR-2013-02-14-199, as amended by FOR-2023-12-11-2000⁴¹⁴²⁴³

Phenibut (fenibut; 4-amino-3-fenylbutansyre) is a narcotic in Norway because it is named in the Narkotikalisten, which was amended with immediate effect on 11 December 2023. Possession and use are prohibited without lawful authority. Manufacture, import, wholesale activity and retail sale require the applicable express authorisation, and narcotic supply, sale and dispatch are permitted only for medical and scientific use.

South AfricaIllegal (analog/blanket ban)Schedule 2 Part III

Drugs and Drug Trafficking Act, 1992, as amended by the Drugs and Drug Trafficking Amendment Act 14 of 2022⁴⁴⁴⁴⁵

Phenibut is analog-covered under Part III of Schedule 2 to the Drugs and Drug Trafficking Act, 1992, as substituted by the Drugs and Drug Trafficking Amendment Act 14 of 2022. Part III lists gamma-hydroxybutyrate (GHB) and extends coverage to chemically related substances with a similar structural fragment and/or similar pharmacodynamic properties; phenibut and GHB both act at GABA-B receptors. Dealing in or possessing a covered undesirable dependence-producing substance is prohibited unless authorized under the Act, and the substituted Schedule was published in Government Gazette 47736 on 14 December 2022.

SwitzerlandNot scheduledVerzeichnisse A–D

Betäubungsmittelverzeichnisverordnung (BetmVV-EDI)⁴⁹⁵⁰

Not listed under Buchstabe A, B, C, or D of controlled substances legislation. Generally considered legal to possess.

ArgentinaIllegalAnexo I

Decreto 560/2019, Anexo I, sustituido por Decreto 122/2026¹⁸¹⁹²⁰

Phenibut (Fenibut; ácido 4-amino-3-fenilbutírico) is an individually listed estupefaciente in Argentina’s Anexo I to Decreto 560/2019. Decreto 122/2026 replaces that annex and keeps the national criminal-control list current; substances in the list are estupefacientes for article 77 of the Código Penal and the offences in Ley 23.737. Unauthorized production, possession, supply, and trafficking of a listed substance are therefore subject to Argentina’s narcotics-law prohibitions.

CanadaUncontrolledCitation needed

Not a controlled substance under Canadian law. Legal to possess without license or prescription.

GermanyIllegal (analog/blanket ban)Anlage 1

Neue-psychoaktive-Stoffe-Gesetz (NpSG)^28293031

Phenibut (4-amino-3-phenylbutanoic acid) is covered by the NpSG’s Annex 1 structural group for compounds derived from 2-phenethylamine, rather than by an individual name. The NpSG prohibits trading, placing on the market, manufacture, import, export, acquisition, possession, and administration of covered substances, subject to statutory exemptions for recognised industrial, commercial, and scientific uses. The Act has been in force since 26 November 2016; the consolidated text is current through the amendment of 7 January 2026.

LatviaPrescription onlyRx

Latvijas Zāļu reģistrs — Noofen 250 mg tabletes³⁴

Available as an unscheduled prescription drug marketed under the brand name 'Noofen.'³⁵ Also sold as 'Cognifen' in combination with ipidacrine for cognitive impairment associated with vascular disorders.

New ZealandPrescription onlyPrescription medicines

Medicines Regulations 1984³⁸³⁹⁴⁰

Phenibut is a prescription medicine listed in Part 1 of Schedule 1 to the Medicines Regulations 1984. The current Schedule 1 was replaced by the Medicines Amendment Regulations (No 2) 2021, which came into force on 1 September 2021. Retail sale or supply of a prescription medicine is restricted by the Medicines Act 1981 to statutory routes and exemptions, including authorised prescribing and dispensing routes.

RussiaApproved pharmaceutical

Added to the State Drug Register in 1974 under Order No. 1126 by the USSR Ministry of Public Health.⁵ Remains available as a neuropsychotropic medication for conditions including anxiety, depression, PTSD, insomnia, and vestibular disorders.

SwedenNot scheduledBilaga 1

Förordning (1992:1554) om kontroll av narkotika; Förordning (1999:58) om förbud mot vissa hälsofarliga varor⁴⁶⁴⁷⁴⁸

Phenibut (4-amino-3-fenylbutansyra) is not named in the current annexes to Sweden's narcotics-control regulation or regulation on goods dangerous to health. Swedish narcotics and hazardous-goods controls apply to substances specified in those respective annexes. Sweden does not use analogue, effect-based, or generic chemical-structure definitions to classify narcotics or goods dangerous to health; the separately named 4-fluorophenibut entry does not extend to phenibut.

United KingdomRestrictedPsychoactive substance

Psychoactive Substances Act 2016^5152535455

Phenibut is a psychoactive substance for the purposes of the Psychoactive Substances Act 2016 when it is not an exempted substance. The Act prohibits producing, supplying, offering to supply, importing, or exporting it where the statutory knowledge and intended psychoactive-consumption conditions are met. The Act does not create a general offence of simple possession outside a custodial institution; medicinal products and controlled drugs are among the statutory exemptions. The Medicines and Healthcare products Regulatory Agency describes phenibut as a central depressant and GABA analogue with anxiolytic effects.

References

Source Pages

Citations

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