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Research · Supplements

Phenibut

Grey marketNot approved for human use in the US, and sold anyway.

Small Russian randomized trials reported less anxiety and better self-rated sleep with phenibut, but compared phenibut regimens with each other or gave no between-group figures. No placebo-controlled trial was sourced. FDA states it is not a lawful dietary ingredient. US poison centers recorded coma in 6% of exposures, and case reviews describe severe withdrawal.

Add to Bio HackChecked 2026-11-09
Status
Not FDA-approved for any use. FDA states phenibut does not meet the definition of a dietary ingredient, so supplements listing it as one are misbranded. Prescribed as a medicine in Russia and Latvia. Illegal to produce, possess or supply in Germany. A Schedule 9 prohibited substance in Australia.
Also called
beta-phenyl-gamma-aminobutyric acid, β-phenyl-GABA, 4-amino-3-phenylbutyric acid, phenibut HCl, fenibut, Noofen, Anvifen
Taken for
anxiety, sleep, stress, social ease, focus, alcohol withdrawal

Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on

Shown to help3

Reported risks6

What people take it for, and what was found

Shown to help3

Limited

Anxiety

Limited evidence: anxiety scores improved on phenibut in studies with no placebo or untreated group, so the effect cannot be separated from time.

The numbers and sources
Effect
In a randomized trial in adults with anxiety disorder, phenibut for 21 days and phenibut for 60 days both improved the measured scores, which covered anxiety, fatigue, sleep, panic attacks and overall symptoms, by the end of treatment (p < 0.05). 30 days after stopping, scores in the 21-day group no longer differed from before treatment, while the 60-day group's improvement persisted (p < 0.05) [1]. A randomized trial in women with tension-type headache compared phenibut added to ibuprofen and tizanidine for 8 weeks with the same two drugs alone, with anxiety among its measures, and its abstract gives no results [2]. In an observational study with no comparison group, adults with adjustment disorder prescribed phenibut in Latvian general practice had symptom scores fall by a mean of 14.8 points (SD 11.3) on a 20-item scale after 3 weeks (p < 0.001) [3].
Population
120 adults with anxiety disorder aged 20 to 70, in four subgroups of 30 [1]. 50 women, mean age 37.4 [2]. 90 adults aged 18 to 70 [3].
Sources
[1], [2], [3]
Caveats
The randomized anxiety trial compared two lengths of phenibut treatment and had no placebo or untreated group, so it cannot separate phenibut's effect from time or expectation [1]. The Latvian study had no comparison group [3]. Both randomized trials were published in Russian with English abstracts [1][2].
Limited

Sleep

One trial found self-rated sleep improved on two forms of phenibut in older adults with insomnia, with no placebo comparison.

The numbers and sources
Effect
In a randomized trial in adults with insomnia and sensitivity to weather, phenibut taken as capsules and phenibut taken as powder emptied from the capsules for 4 weeks both improved total scores on a subjective sleep questionnaire (p = 0.00001 and p = 0.000001). The powder group scored higher on sleep quality (p = 0.00027) and quality of awakening (p = 0.00001) [4].
Population
67 adults aged 60 to 70, 33 on capsules and 34 on powder [4].
Sources
[4]
Caveats
Both groups took phenibut, so the trial compared two forms of it. It did not compare phenibut with placebo or no treatment. Sleep was self-rated. Published in Russian with an English abstract [4].
Limited

Focus, attention and mental fatigue

Limited evidence: small trials in children with ADHD and adults with fatigue reported better attention, without between-group figures.

The numbers and sources
Effect
In an open-label randomized trial in children with ADHD, one month of phenibut was compared with low-dose multivitamins. The abstract reports improved self-control, sustained, directed and divided attention, and verbal memory by the end of treatment, without between-group figures [5]. In a randomized trial in adults with cerebrovascular disease and persistent fatigue, phenibut added to standard therapy was compared with standard therapy alone. Three quarters of the phenibut group had a 30% to 50% fall in fatigue intensity, and the abstract reports improved scores on the Schulte attention test, without figures for the control group [6].
Population
50 children with ADHD in two equal groups [5]. 53 adults, 33 on phenibut and 20 on standard therapy alone [6].
Sources
[5], [6]
Caveats
Neither abstract gives a between-group comparison. The ADHD trial was open-label [5]. Both were published in Russian. No trial in healthy adults was located.

Claimed, not studied in people2

Untested

Stress and social ease

Not studied in people. A review of online drug forums found people take phenibut for anxiety relief and euphoria, and often report tolerance and withdrawal.

No study in people. This rests on what users report, documented traditional use, how it acts in the body.

The numbers and sources
Effect
A 2015 survey of online drug discussion forums and the medical literature found phenibut is taken for its anxiety-relieving and euphoric properties, with tolerance and withdrawal commonly reported as adverse effects [20]. A pharmacology review describes phenibut as acting mainly at GABA-B receptors, and as widely used in Russia to relieve tension, anxiety and fear [21].
Population
Online forum posts and published case reports [20]. Pharmacology and clinical use in Russia [21].
Sources
[20], [21]
Caveats
Forum reports are self-selected and unverified, and they describe what users seek, not what a controlled study measured. No trial of phenibut for everyday stress or social situations was located.
Untested

Alcohol withdrawal

Not studied in people. Phenibut is used in Russia to treat alcohol withdrawal, and it acts mainly on GABA-B receptors in the brain.

No study in people. This rests on documented traditional use, how it acts in the body.

The numbers and sources
Effect
A study of supplements sold in the US notes that phenibut is used to treat anxiety, insomnia, alcohol withdrawal and other conditions in Russia [9]. A pharmacology review describes it as a GABA-mimetic acting mainly at GABA-B and to some extent GABA-A receptors [21].
Population
Medical use in Russia, as described in published reviews [9][21].
Sources
[9], [21]
Caveats
A statement of how it is used, not a measured result. No trial of phenibut for alcohol withdrawal was located in English-language databases. Phenibut causes its own withdrawal syndrome, described under Risks.

Risks

Reported risks6

Limited

FDA regulatory position and actions

FDA states phenibut does not meet the definition of a dietary ingredient, and supplements declaring it as one are misbranded.

The numbers and sources
Effect
FDA states that phenibut does not meet the statutory definition of a dietary ingredient, and that supplements declaring it as one are misbranded. On April 10, 2019, FDA sent warning letters to three companies marketing supplements labeled to contain phenibut [7][8]. In June 2023, a federal court entered a permanent injunction against a seller whose products allegedly contained phenibut HCl. In that case FDA stated that phenibut HCl is not a permitted food additive [7].
Population
Products sold in the US [7][8].
Sources
[7], [8]
Caveats
Regulatory actions, not studies of harm. FDA's phenibut page does not list adverse effects [7].
Limited

Product contents

Limited evidence: small product tests found phenibut amounts far from the label, with undeclared ingredients in all six internet samples.

The numbers and sources
Effect
Four supplement brands labeled as containing phenibut were tested before and after FDA's warnings. Before, two contained phenibut. After, all four did, and the amount rose in three [9]. In six phenibut products bought from three internet suppliers, three held substantially less phenibut than their labels claimed and one held considerably more. All contained declared and undeclared ingredients found in other dietary supplements [10]. A 2020 to 2024 market surveillance study by 12 official medicines control laboratories in Europe and Australia intercepted phenibut as large bulk quantities of raw material [11].
Population
4 US supplement brands [9]. 6 samples from 3 internet suppliers [10]. 159 samples of products with unauthorized nootropic ingredients [11].
Sources
[9], [10], [11]
Caveats
Small samples of products. The combinations of phenibut with undeclared ingredients have not been tested for activity or safety, as the authors of [10] note.
Limited

Poison center reports

Limited evidence: of 1,320 US poison center phenibut exposures, 12.6% had major, life-threatening effects and three people died.

The numbers and sources
Effect
From 2009 to 2019, US poison centers recorded 1,320 phenibut exposures, rising sharply after 2015. The most common effects were agitation (30.4%), drowsiness (29.0%), fast heart rate (21.9%) and confusion (21.3%). Coma occurred in 6.2%. Major, life-threatening effects occurred in 12.6%, and three deaths were reported. Among phenibut-only exposures, 10.2% had major effects [12]. A Minnesota poison center recorded 56 calls from 2000 to 2018, 86% in the last five years. 19.6% of patients were intubated, and 10.7% had withdrawal concerns [13]. A poison center in northern Germany received 17 inquiries about phenibut from 2008 to 2022. Overdoses were reported in 15, and 8 of those people were somnolent. No respiratory depression or coma was recorded [14].
Population
Exposures reported to US poison centers [12][13] and to a German poison center [14].
Sources
[12], [13], [14]
Caveats
Other substances were involved in 40.2% of adult US cases [12]. Reports are voluntary and cannot give a rate among all users.
Limited

Toxicity and withdrawal in case reports

Case reports: toxicity brought altered mental state and psychosis, often needing intubation, and withdrawal brought agitation, insomnia, psychosis and sometimes seizures.

The numbers and sources
Effect
A systematic review of 62 published cases found altered mental state, sleepiness, psychosis and movement disorders in toxicity, and 48.7% of toxicity cases needed intubation. Withdrawal brought anxiety, agitation, insomnia and psychosis. 95.7% of withdrawal cases involved daily use, and 69.6% needed several medicines to treat. Hospital stays averaged 5.0 days for toxicity and 7.7 days for withdrawal [15]. A review of 22 withdrawal cases found severe psychomotor agitation, with signs that can mimic serotonin syndrome or neuroleptic malignant syndrome [16]. A 2023 systematic review of 25 withdrawal reports found seizures in 8%, intubation in 24% and intensive care admission in 44%. Withdrawal began as soon as two hours after the last dose, and 76% needed at least two drug therapies [17].
Population
Published case reports and conference abstracts [15][16][17].
Sources
[15], [16], [17]
Caveats
63.2% of cases in [15] also involved other addictive substances, mostly benzodiazepines and alcohol. In [17], patterns and outcomes were similar with phenibut alone and with other substances. Case reports cannot give a rate.
Limited

Adverse events in clinical trials

Limited evidence: in 11 trials, adverse events occurred in 5.66% of patients, mostly sleepiness. The trials were not designed to detect dependence.

The numbers and sources
Effect
A systematic review of 11 clinical trials (583 patients), mostly from Eastern Europe, found adverse events in 5.66% of patients, most often sleepiness (1.89%). The authors note that these differ from the dependence and intoxication seen in case reports [18].
Population
Patients in prescribed-use trials and 16 patients in case reports [18].
Sources
[18]
Caveats
Most authors were from the Latvian Institute of Organic Synthesis [18]. The trials were not designed to detect dependence.
Limited

Status in Australia and Germany

Australia lists phenibut in Schedule 9 as a prohibited substance, and a review states it is illegal in Germany and a prescription drug in Russia.

The numbers and sources
Effect
Australia's Poisons Standard lists phenibut in Schedule 9, prohibited substances. These are substances that may be abused or misused, whose manufacture, possession, supply or use is to be prohibited by law except for approved research, analytical, teaching or training purposes [19]. A 2024 review states that phenibut is a prescription drug in Russia and that its production, possession, use, trafficking or administration is illegal in Germany [14].
Population
Australia [19]. Germany and Russia [14].
Sources
[19], [14]
Caveats
Regulatory classifications. Status in other countries was not checked for this page.

Sources

  1. Esin OR, Khayrullin IK, Esin RG, Malova LA. The effectiveness of short and prolonged course treatment of anxiety with Anvifen. Zhurnal Nevrologii i Psikhiatrii imeni S.S. Korsakova. 2022. https://doi.org/10.17116/jnevro202212212168
  2. Duma SN. A role of treatment of autonomic syndrome in patients with tension-type headache. Zhurnal Nevrologii i Psikhiatrii imeni S.S. Korsakova. 2015. https://doi.org/10.17116/jnevro20151152168-70
  3. Tērauds E, Dansone G, Troshina Y. Efficacy of Noofen 250 mg Capsules for the Management of Anxious-Neurotic Symptoms in Patients with Adjustment Disorder. Journal of Clinical Medicine. 2025. https://doi.org/10.3390/jcm14155570
  4. Esin RG, Esin OR, Khayrullin IK, Erkinova DE, Khaibullina DK. Effectiveness of Anvifen in the treatment of insomnia in elderly patients. Zhurnal Nevrologii i Psikhiatrii imeni S.S. Korsakova. 2024. https://doi.org/10.17116/jnevro202412402191
  5. Zavadenko NN, Suvorinova NIu. The results of the pharmacological treatment of attention deficit hyperactivity disorder: evaluation with neuropsychological methods. Zhurnal Nevrologii i Psikhiatrii imeni S.S. Korsakova. 2014. https://pubmed.ncbi.nlm.nih.gov/25403296/
  6. Vorob'eva OV, Rusaya VV. Efficacy and safety of noophen in the treatment of chronic fatigue syndrome in patients with cerebrovascular insufficiency. Zhurnal Nevrologii i Psikhiatrii imeni S.S. Korsakova. 2017. https://doi.org/10.17116/jnevro201711711131-36
  7. U.S. Food and Drug Administration. Phenibut in Dietary Supplements. 2023. https://www.fda.gov/food/information-select-dietary-supplement-ingredients-and-other-substances/phenibut-dietary-supplements
  8. U.S. Food and Drug Administration. Warning Letter: Atomixx, MARCS-CMS 576505. 2019. https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/atomixx-576505-04102019
  9. Cohen PA, Ellison RR, Travis JC, et al. Quantity of phenibut in dietary supplements before and after FDA warnings. Clinical Toxicology. 2022. https://doi.org/10.1080/15563650.2021.1973020
  10. Upmanis T, Sevostjanovs E, Zvejniece L, et al. Purchasing "Nootropics" Online: Identification and Quantification of Ingredients in Phenibut-Containing Products. Medicina. 2024. https://doi.org/10.3390/medicina60101561
  11. Vanhee C, Deconinck E, George M, et al. The Occurrence of Illicit Smart Drugs or Nootropics in Europe and Australia and Their Associated Dangers: Results from a Market Surveillance Study by 12 Official Medicines Control Laboratories. Journal of Xenobiotics. 2025. https://doi.org/10.3390/jox15030088
  12. Graves JM, Dilley J, Kubsad S, et al. Notes from the Field: Phenibut Exposures Reported to Poison Centers, United States, 2009 to 2019. Morbidity and Mortality Weekly Report. 2020. https://doi.org/10.15585/mmwr.mm6935a5
  13. McCabe DJ, Bangh SA, Arens AM, et al. Phenibut exposures and clinical effects reported to a regional poison center. The American Journal of Emergency Medicine. 2019. https://doi.org/10.1016/j.ajem.2019.02.044
  14. Bonnet U, Scherbaum N, Schaper A, Soyka M. Phenibut, an illegal food supplement with psychotropic effects and health risks. Deutsches Ärzteblatt International. 2024. https://doi.org/10.3238/arztebl.m2024.0003
  15. Weleff J, Kovacevich A, Burson J, et al. Clinical Presentations and Treatment of Phenibut Toxicity and Withdrawal: A Systematic Literature Review. Journal of Addiction Medicine. 2023. https://doi.org/10.1097/adm.0000000000001141
  16. Hardman MI, Sprung J, Weingarten TN. Acute phenibut withdrawal: A comprehensive literature review and illustrative case report. Bosnian Journal of Basic Medical Sciences. 2018. https://doi.org/10.17305/bjbms.2018.4008
  17. Feldman R, Autry B, Dukes J, et al. A systematic review of phenibut withdrawal focusing on complications, therapeutic approaches, and single substance versus polysubstance withdrawal. Clinical Toxicology. 2023. https://doi.org/10.1080/15563650.2023.2285702
  18. Kupats E, Vrublevska J, Zvejniece B, et al. Safety and Tolerability of the Anxiolytic and Nootropic Drug Phenibut: A Systematic Review of Clinical Trials and Case Reports. Pharmacopsychiatry. 2020. https://doi.org/10.1055/a-1151-5017
  19. Australian Government. Therapeutic Goods (Poisons Standard, February 2026) Instrument 2026, Schedule 9. Federal Register of Legislation F2026L00060. 2026. https://www.legislation.gov.au/F2026L00060/asmade/2026-01-30/text/original/pdf
  20. Owen DR, Wood DM, Archer JRH, Dargan PI. Phenibut (4-amino-3-phenyl-butyric acid): Availability, prevalence of use, desired effects and acute toxicity. Drug and Alcohol Review. 2016. https://doi.org/10.1111/dar.12356
  21. Lapin I. Phenibut (beta-phenyl-GABA): a tranquilizer and nootropic drug. CNS Drug Reviews. 2001. https://doi.org/10.1111/j.1527-3458.2001.tb00211.x

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