Phenibut

updated

Phenibut (beta-phenyl-GABA), related to baclofen, is a Russian prescription medicine with no FDA-approved product. Its anxiety and sleep claims rest on a Russian leaflet and small, mostly uncontrolled or active-comparator trials, and a PubMed search on 10 October 2026 found no placebo-controlled trial. The published downside is large: dependence with withdrawal beginning within hours in case reports, 1,320 US poison-center exposures from 2009 to 2019 with 3 deaths reported, and FDA's position that supplements containing it are misbranded.

GABA analogue (beta-phenyl-GABA), related to baclofen

  • A Russian leaflet lists asthenic and anxiety-neurotic states and insomnia and night anxiety in the elderly among the uses, and says the drug reduces anxiety and tension and normalizes sleep without sedation or excitement.
  • FDA says phenibut does not meet the statutory definition of a dietary ingredient, so supplements declaring it are misbranded, and records a permanent injunction entered on 2 June 2023.
  • A PubMed search on 10 October 2026 returned 9 records, and none was a placebo-controlled trial of anxiety or sleep.
  • US poison centers received 1,320 phenibut exposure calls from 2009 to 2019, with major effects in 12.6% of exposures and 3 deaths reported.
  • In a systematic review of 25 withdrawal cases, 11 (44%) were admitted to intensive care and 6 (24%) were intubated.
  • A 2024 German review states phenibut production, possession, use and trafficking are illegal in Germany.

What is phenibut, and what is its regulatory status?

Phenibut (beta-phenyl-GABA), related to baclofen, is a Russian prescription medicine. No FDA-approved phenibut drug turned up, FDA says supplements containing it are misbranded, and a 2024 German review says it is illegal in Germany.

A Russian leaflet for Phenibut 250 mg tablets (phenibut hydrochloride, registration number LSR-002562/09 printed in Cyrillic letters) lists asthenic and anxiety-neurotic states, stuttering, tics and bedwetting in children, insomnia and night anxiety in the elderly, Meniere disease and vestibular dizziness, motion-sickness prevention, and alcohol withdrawal as part of combined therapy. Its pharmacodynamics section says the drug reduces anxiety and tension and normalizes sleep, without sedation or excitement. These are label descriptions, not trial results. The leaflet was read as a copy hosted on a drug-information site, its version date is not shown, and a Russian registration is not an FDA or EMA review.

FDA's page Phenibut in Dietary Supplements says phenibut does not meet the statutory definition of a dietary ingredient, so any supplement declaring it as a dietary ingredient is misbranded. It records warning letters to three companies in April 2019 and a permanent injunction entered on 2 June 2023 against an individual doing business as Chill6, whose beverage powders contained phenibut HCl and were labeled to treat insomnia, alcoholism, PTSD and anxiety disorder. The page is current as of 12 July 2023.

On 10 October 2026, openFDA Drugs@FDA searches on the generic names phenibut, fenibut and aminophenylbutyric acid each returned no matches, and a DailyMed label search for phenibut returned no labels. A 2024 German review states phenibut is a prescription drug in Russia but that its production, possession, use, trafficking and administration are illegal in Germany. That legal status was read from the review, not from German legislation, and status in other countries was not examined.

Phenibut (4-amino-3-phenylbutanoic acid) is PubChem CID 14113 (C10H13NO2, 179.22 g/mol, CAS 1078-21-3). The hydrochloride, which the Russian tablets and most trials used, is CID 11499499 (C10H14ClNO2, 215.67 g/mol, CAS 3060-41-1). The drug is a racemate and R-phenibut carries the receptor activity. Baclofen is the 4-chlorophenyl derivative of phenibut (CID 2284, C10H12ClNO2, 213.66 g/mol, CAS 1134-47-0). A vendor phenibut may be the free base or the hydrochloride, which differ in molecular weight by about 20%.

Phenibut leaflet: anxiety-neurotic and sleep uses, label wording on anxiety and sleep

Official label

Russian-language patient leaflet for Phenibut 250 mg tablets (phenibut hydrochloride), registration number LSR-002562/09 printed in Cyrillic letters. Copy hosted on medi.ru; version date not shown.

The leaflet lists asthenic and anxiety-neurotic states, stuttering, tics and bedwetting in children, insomnia and night anxiety in the elderly, Meniere disease and vestibular dizziness, motion-sickness prevention, and alcohol withdrawal as part of combined therapy. The pharmacodynamics section says the drug reduces anxiety and tension and normalizes sleep, without sedation or excitement. It lists drowsiness, nausea, irritability, agitation, anxiety, dizziness, headache and allergic reactions as side effects, names fatty liver degeneration, eosinophilia, low blood pressure and kidney impairment under overdose, and contraindicates pregnancy, breastfeeding and age under 3.

Participants / model
Adults and children over 3
Treatment
Phenibut hydrochloride 250 mg oral tablets
Follow-up
Version date not shown
Study design
Russian-language patient leaflet, copy hosted on a drug-information site
Funding
not stated in the source

These are label descriptions, not trial results. A Russian registration is not an FDA or EMA review. The copy was read on a commercial drug-information site, not on the Russian state register.

Read the original source
FDA: not a dietary ingredient; warning letters April 2019, injunction 2 June 2023

Regulatory record

U.S. Food and Drug Administration. Phenibut in Dietary Supplements, page current as of 12 July 2023.

FDA says phenibut does not meet the statutory definition of a dietary ingredient, so any supplement declaring it as a dietary ingredient is misbranded. The page records warning letters to three companies in April 2019 and a permanent injunction entered on 2 June 2023 against an individual doing business as Chill6, whose beverage powders contained phenibut HCl and were labeled to treat insomnia, alcoholism, PTSD and anxiety disorder.

Participants / model
Not a clinical population
Treatment
Dietary supplement products containing phenibut
Follow-up
Page current as of 12 July 2023
Study design
Official FDA record
Funding
not stated in the source

Later FDA actions were not examined.

Read the original source
Searches, 10 October 2026: no FDA application or label

Regulatory record

U.S. Food and Drug Administration. openFDA Drugs@FDA searches on the generic names phenibut, fenibut and aminophenylbutyric acid, with a DailyMed label search for phenibut, run on 10 October 2026.

Each openFDA Drugs@FDA search returned No matches found, and the DailyMed search returned no labels. No FDA-approved phenibut drug turned up.

Participants / model
Records reviewed, not a population
Treatment
Not applicable
Follow-up
Searches run on 10 October 2026
Study design
Dated regulator database search
Funding
not stated in the source

The result covers FDA application and label records only.

Read the original source
German review: illegal in Germany; 17 poison-center inquiries, no respiratory depression or coma

Narrative review

Bonnet U et al. Dtsch Arztebl Int. 2024;121(7):222-227. PMID 38377332.

The review states phenibut is a prescription drug in Russia but that its production, possession, use, trafficking and administration are illegal in Germany. The regional poison center behind the review (GIZ-Nord) logged 17 phenibut inquiries from 2008 to 2022, with overdoses of 2 to 100 g in 15 of the 17, somnolence in 8, and no respiratory depression or coma, including after 100 g. The authors note no phenibut deaths had been published in Germany or elsewhere in Western Europe, and that such cases may have been overlooked.

Participants / model
Poison-center callers in northern Germany and published cases
Treatment
Phenibut taken orally, mostly as an unregulated supplement
Follow-up
Inquiries from 2008 to 2022
Study design
Narrative review with regional poison-center data
Funding
not stated in the source

Legal status was read from this review, not from German legislation. Legal status outside the US and Germany was not examined.

Read the original source
PubChem: phenibut base, hydrochloride and baclofen identity

Chemical identity record

National Library of Medicine. PubChem compound records CID 14113 (phenibut), CID 11499499 (phenibut hydrochloride) and CID 2284 (baclofen).

Phenibut (4-amino-3-phenylbutanoic acid, beta-phenyl-GABA): PubChem CID 14113, C10H13NO2, 179.22 g/mol, CAS 1078-21-3. The hydrochloride, which is what the Russian tablets and most trials used: CID 11499499, C10H14ClNO2, 215.67 g/mol, CAS 3060-41-1. The drug is a racemate and R-phenibut carries the receptor activity. Baclofen: CID 2284, C10H12ClNO2, 213.66 g/mol, CAS 1134-47-0. Baclofen is the 4-chlorophenyl derivative of phenibut.

Participants / model
Chemical identity, not a clinical population
Treatment
Defined free base, hydrochloride salt and racemate
Follow-up
Not applicable
Study design
NLM chemical record
Funding
not stated in the source

A vendor phenibut may be the free base or the hydrochloride, which differ in molecular weight by about 20%. Identity record only; it says nothing about efficacy or safety.

Read the original source

What have the clinical studies of phenibut found?

The clinical literature is small. A systematic review pooled 11 phenibut trials (583 patients) and reported adverse events in 5.66% of trial patients, but the abstract gives no trial designs, and the nearest trials found were active-comparator or uncontrolled Russian studies.

A systematic review pooled 11 phenibut clinical trials (583 patients) and 14 case reports of dependence or intoxication (16 patients). Trial adverse events occurred in 5.66% of patients, the most common being somnolence (1.89%). The authors conclude phenibut is well tolerated at therapeutic doses and say the quality of online-bought product and the role of alcohol and other drugs remain open. The abstract does not give the trial designs, and the authors are from Latvian institutions.

The nearest trials in a PubMed search on 10 October 2026 were a randomized comparison in 62 patients with cerebrovascular disease and anxiety given phenibut hydrochloride (marketed as noophen, n = 33) or adaptol (n = 29), with no placebo, where anxiety symptoms stopped in 79.0% of patients across both groups and sleep disorders fell in the phenibut group. The others were an open randomized trial in 50 children with ADHD versus multivitamins, a 30-adolescent comparison with adaptol, and a 30-patient uncontrolled series in tension headache.

Systematic review: 11 trials (583 patients), 14 case reports (16 patients)

Systematic review and meta-analysis

Kupats E et al. Pharmacopsychiatry. 2020;53(5):201-208. PMID 32340063.

The review pooled 11 phenibut clinical trials (583 patients) and 14 case reports of dependence or intoxication (16 patients). Trial adverse events occurred in 5.66% of patients, the most common being somnolence (1.89%). In the case reports the doses were 0.5 to 100 g a day, with cardiovascular effects, insomnia, anxiety, agitation, hallucinations and depressed consciousness. The authors conclude phenibut is well tolerated at therapeutic doses and say the quality of online-bought product and the role of alcohol and other drugs remain open.

Participants / model
Patients in clinical trials and people in case reports
Treatment
Oral phenibut
Follow-up
Not stated in the source
Study design
Systematic review of 11 clinical trials and 14 case reports
Funding
not stated in the source

The abstract does not give the trial designs, and the authors are from Latvian institutions.

Read the original source
PubMed search, 10 October 2026: 9 records, none a placebo-controlled anxiety or sleep trial

PubMed search record

PubMed search run on 10 October 2026: (phenibut OR fenibut OR phenigam OR noofen) AND (randomized OR randomised OR placebo OR double-blind OR controlled OR open-label) AND (anxiety OR insomnia OR sleep OR neurosis OR asthenia OR stress OR patients). 9 records returned.

The search returned 9 records, and the abstract of each was read. None was a placebo-controlled trial of anxiety or sleep. The nearest were a randomized comparison in 62 patients with cerebrovascular disease and anxiety given phenibut hydrochloride (marketed as noophen, n = 33) or adaptol (n = 29) with no placebo, where anxiety symptoms stopped in 79.0% of patients across both groups and sleep disorders fell in the phenibut group (PMID 28300804); an open randomized trial in 50 children with ADHD versus multivitamins (PMID 25403296); a 30-adolescent comparison with adaptol (PMID 25726788); and a 30-patient uncontrolled series in tension headache (PMID 28805758). A 1997 study in volunteers under heat stress included a placebo arm, bemethyl 0.5 g and phenibut 0.25 g, but measured heat tolerance, not anxiety or sleep (PMID 9235216). The anxiety and sleep claim has no placebo-controlled human trial among these records.

Participants / model
Records returned, not a population
Treatment
Not applicable
Follow-up
Search run on 10 October 2026
Study design
Literature search
Funding
not stated in the source

A search result shows what PubMed returned on that date. It is not proof that no unindexed study exists. The 1997 heat study appears only as an abstract fragment.

Read the original source

Does phenibut relieve anxiety and improve sleep?

Anxiolysis and better sleep appear in the Russian leaflet and in uncontrolled Russian reports, but no placebo-controlled trial of either outcome turned up. A PubMed search on 10 October 2026 returned 9 records, and the best-documented part of the literature is dependence and withdrawal.

Sellers say phenibut (beta-phenyl-GABA, related to baclofen) relieves anxiety and improves sleep. The Russian leaflet says the drug reduces anxiety and tension and normalizes sleep, without sedation or excitement, but that is a label description, not a trial result.

A PubMed search on 10 October 2026 for phenibut, fenibut, phenigam or noofen with randomized, placebo, double-blind, controlled or open-label terms and anxiety, insomnia, sleep, neurosis, asthenia, stress or patients returned 9 records, and the abstract of each was read. None was a placebo-controlled trial of anxiety or sleep. A 1997 study in volunteers under heat stress included a placebo arm, bemethyl 0.5 g and phenibut 0.25 g, but measured heat tolerance, not anxiety or sleep.

The comparisons that exist are against adaptol or multivitamins, or have no comparison group, so they cannot separate the effect of phenibut from placebo.

PubMed search, 10 October 2026: 9 records, none a placebo-controlled anxiety or sleep trial

PubMed search record

PubMed search run on 10 October 2026: (phenibut OR fenibut OR phenigam OR noofen) AND (randomized OR randomised OR placebo OR double-blind OR controlled OR open-label) AND (anxiety OR insomnia OR sleep OR neurosis OR asthenia OR stress OR patients). 9 records returned.

The search returned 9 records, and the abstract of each was read. None was a placebo-controlled trial of anxiety or sleep. The nearest were a randomized comparison in 62 patients with cerebrovascular disease and anxiety given phenibut hydrochloride (marketed as noophen, n = 33) or adaptol (n = 29) with no placebo, where anxiety symptoms stopped in 79.0% of patients across both groups and sleep disorders fell in the phenibut group (PMID 28300804); an open randomized trial in 50 children with ADHD versus multivitamins (PMID 25403296); a 30-adolescent comparison with adaptol (PMID 25726788); and a 30-patient uncontrolled series in tension headache (PMID 28805758). A 1997 study in volunteers under heat stress included a placebo arm, bemethyl 0.5 g and phenibut 0.25 g, but measured heat tolerance, not anxiety or sleep (PMID 9235216). The anxiety and sleep claim has no placebo-controlled human trial among these records.

Participants / model
Records returned, not a population
Treatment
Not applicable
Follow-up
Search run on 10 October 2026
Study design
Literature search
Funding
not stated in the source

A search result shows what PubMed returned on that date. It is not proof that no unindexed study exists. The 1997 heat study appears only as an abstract fragment.

Read the original source
Phenibut leaflet: anxiety-neurotic and sleep uses, label wording on anxiety and sleep

Official label

Russian-language patient leaflet for Phenibut 250 mg tablets (phenibut hydrochloride), registration number LSR-002562/09 printed in Cyrillic letters. Copy hosted on medi.ru; version date not shown.

The leaflet lists asthenic and anxiety-neurotic states, stuttering, tics and bedwetting in children, insomnia and night anxiety in the elderly, Meniere disease and vestibular dizziness, motion-sickness prevention, and alcohol withdrawal as part of combined therapy. The pharmacodynamics section says the drug reduces anxiety and tension and normalizes sleep, without sedation or excitement. It lists drowsiness, nausea, irritability, agitation, anxiety, dizziness, headache and allergic reactions as side effects, names fatty liver degeneration, eosinophilia, low blood pressure and kidney impairment under overdose, and contraindicates pregnancy, breastfeeding and age under 3.

Participants / model
Adults and children over 3
Treatment
Phenibut hydrochloride 250 mg oral tablets
Follow-up
Version date not shown
Study design
Russian-language patient leaflet, copy hosted on a drug-information site
Funding
not stated in the source

These are label descriptions, not trial results. A Russian registration is not an FDA or EMA review. The copy was read on a commercial drug-information site, not on the Russian state register.

Read the original source

What do phenibut supplements contain?

Content can be higher and less predictable than the prescription tablet. In 4 supplement brands tested before and after FDA warnings, all 4 contained phenibut afterward, at 21 to 1,164 mg per serving, and the highest amount was up to 450% above a typical Russian pharmaceutical tablet.

In 4 phenibut dietary-supplement brands tested before and after FDA warnings, 2 of 4 contained phenibut before (484 and 487 mg per serving), and all 4 contained it afterward, at 21 to 1,164 mg per serving. Two brands showed phenibut only after the warnings, and the amount rose in 3 of the 4 products. The highest amount was up to 450% above a typical Russian pharmaceutical tablet.

This is a very small product sample, not a study in people, but it shows supplement content can be higher and less predictable than the prescription product.

4 supplement brands: 21 to 1,164 mg per serving after the FDA warnings

Analytical product survey

Cohen PA et al. Clin Toxicol (Phila). 2022;60(4):486-488. PMID 34550038.

In 4 phenibut dietary-supplement brands tested before and after FDA warnings, 2 of 4 contained phenibut before (484 and 487 mg per serving), and all 4 contained it afterward, at 21 to 1,164 mg per serving. Two brands showed phenibut only after the warnings, and the amount rose in 3 of the 4 products. The highest amount was up to 450% above a typical Russian pharmaceutical tablet.

Participants / model
4 commercial supplement brands
Treatment
Dietary supplements, mixed forms
Follow-up
Before and after FDA warnings
Study design
Analytical product survey
Funding
not stated in the source

A very small sample, but it shows supplement content can be higher and less predictable than the prescription product. A product analysis, not a study in people.

Read the original source

How does phenibut work, and what does the body do with it?

In rodent and in vitro work, R-phenibut binds the GABA-B receptor, with weaker affinity than baclofen, and also binds the alpha2-delta subunit of calcium channels. No human pharmacokinetic data appear in the sources reviewed.

In GABA-B receptor binding experiments and rodent tests, racemic phenibut bound the receptor with an affinity constant of 177 micromolar, R-phenibut 92 micromolar and baclofen 6.0 micromolar, and S-phenibut was inactive, so the activity of the racemic drug comes from R-phenibut. A second paper found R-phenibut also binds the alpha2-delta subunit of voltage-dependent calcium channels in rat brain membranes (Ki 23 micromolar versus 0.05 micromolar for gabapentin).

This supports the baclofen and gabapentinoid relationship, but it is animal and in vitro work and says nothing about anxiety or sleep in people. No human pharmacokinetic data appear in the sources reviewed.

Rodent and in vitro: GABA-B affinity 177 micromolar racemic, 92 R-phenibut, 6.0 baclofen

Animal study

Dambrova M et al. Eur J Pharmacol. 2008;583(1):128-34. PMID 18275958.

In GABA-B receptor binding experiments and rodent tests, racemic phenibut bound the receptor with an affinity constant of 177 micromolar, R-phenibut 92 micromolar and baclofen 6.0 micromolar, and S-phenibut was inactive, so the activity of the racemic drug comes from R-phenibut. A second paper (PMID 26234470) found R-phenibut also binds the alpha2-delta subunit of voltage-dependent calcium channels (Ki 23 micromolar versus 0.05 micromolar for gabapentin) in rat brain membranes.

Participants / model
Rats and mice, with in vitro receptor binding
Treatment
Phenibut isomers and baclofen in assays and rodent tests; route and dose not stated in the source
Follow-up
Not stated in the source
Study design
Original animal and in vitro study
Funding
not stated in the source

This supports the baclofen and gabapentinoid relationship but is animal and in vitro work and says nothing about anxiety or sleep in people. Endpoints were GABA-B binding affinity and locomotor, antidepressant and pain tests.

Read the original source
PubChem: phenibut base, hydrochloride and baclofen identity

Chemical identity record

National Library of Medicine. PubChem compound records CID 14113 (phenibut), CID 11499499 (phenibut hydrochloride) and CID 2284 (baclofen).

Phenibut (4-amino-3-phenylbutanoic acid, beta-phenyl-GABA): PubChem CID 14113, C10H13NO2, 179.22 g/mol, CAS 1078-21-3. The hydrochloride, which is what the Russian tablets and most trials used: CID 11499499, C10H14ClNO2, 215.67 g/mol, CAS 3060-41-1. The drug is a racemate and R-phenibut carries the receptor activity. Baclofen: CID 2284, C10H12ClNO2, 213.66 g/mol, CAS 1134-47-0. Baclofen is the 4-chlorophenyl derivative of phenibut.

Participants / model
Chemical identity, not a clinical population
Treatment
Defined free base, hydrochloride salt and racemate
Follow-up
Not applicable
Study design
NLM chemical record
Funding
not stated in the source

A vendor phenibut may be the free base or the hydrochloride, which differ in molecular weight by about 20%. Identity record only; it says nothing about efficacy or safety.

Read the original source

What risks do the poison-center and clinical reports show?

Dependence and severe withdrawal are documented in case reports, with onset as soon as 2 hours after the last dose. US poison centers received 1,320 exposure calls from 2009 to 2019, with major effects in 12.6% of exposures and 3 deaths reported, and trial adverse events were 5.66%.

US poison centers received 1,320 phenibut exposure calls from 2009 to 2019, rising sharply after 2015. Of exposures, 58.4% were in adults aged 18 to 34, and 75.5% were in men. Reported effects included agitation (30.4%), drowsiness or lethargy (29.0%), tachycardia (21.9%) and confusion (21.3%). Coma occurred in 80 cases (6.2%). Major effects occurred in 12.6% of exposures, and 3 deaths were reported. Among exposures where phenibut was the only agent, 10.2% had major effects, including one death. Exposure calls are not laboratory confirmed, and the report says the reason for the rise is not known.

A regional German poison center logged 17 phenibut inquiries from 2008 to 2022, with overdoses of 2 to 100 g in 15 of the 17, somnolence in 8, and no respiratory depression or coma, including after 100 g. The authors note no phenibut deaths had been published in Germany or elsewhere in Western Europe, and that such cases may have been overlooked.

In 11 pooled clinical trials, adverse events occurred in 5.66% of patients, the most common being somnolence (1.89%). In 14 case reports of dependence or intoxication the doses were 0.5 to 100 g a day, with cardiovascular effects, insomnia, anxiety, agitation, hallucinations and depressed consciousness. The Russian leaflet lists drowsiness, nausea, irritability, agitation, anxiety, dizziness, headache and allergic reactions as side effects, names fatty liver degeneration, eosinophilia, low blood pressure and kidney impairment under overdose, and contraindicates pregnancy, breastfeeding and age under 3.

US poison centers: 1,320 exposure calls, major effects in 12.6%, 3 deaths

Human study

Graves JM et al. MMWR Morb Mortal Wkly Rep. 2020;69(35):1227-1228. PMID 32881852.

US poison centers received 1,320 phenibut exposure calls from 2009 to 2019, rising sharply after 2015. Of exposures, 58.4% were in adults aged 18 to 34, and 75.5% were in men. Reported effects included agitation (30.4%), drowsiness or lethargy (29.0%), tachycardia (21.9%) and confusion (21.3%). Coma occurred in 80 cases (6.2%). Major effects occurred in 12.6% of exposures, and 3 deaths were reported. Among exposures where phenibut was the only agent, 10.2% had major effects, including one death.

Participants / model
People exposed to phenibut, mostly adults aged 18 to 34
Treatment
Phenibut tablets (65.1%) or powder (24.8%) among known forms, mostly ingested
Follow-up
2009 to 2019
Study design
National surveillance report (MMWR)
Funding
not stated in the source

Exposure calls are not laboratory confirmed, and the report says the reason for the rise is not known.

Read the original source
German review: illegal in Germany; 17 poison-center inquiries, no respiratory depression or coma

Narrative review

Bonnet U et al. Dtsch Arztebl Int. 2024;121(7):222-227. PMID 38377332.

The review states phenibut is a prescription drug in Russia but that its production, possession, use, trafficking and administration are illegal in Germany. The regional poison center behind the review (GIZ-Nord) logged 17 phenibut inquiries from 2008 to 2022, with overdoses of 2 to 100 g in 15 of the 17, somnolence in 8, and no respiratory depression or coma, including after 100 g. The authors note no phenibut deaths had been published in Germany or elsewhere in Western Europe, and that such cases may have been overlooked.

Participants / model
Poison-center callers in northern Germany and published cases
Treatment
Phenibut taken orally, mostly as an unregulated supplement
Follow-up
Inquiries from 2008 to 2022
Study design
Narrative review with regional poison-center data
Funding
not stated in the source

Legal status was read from this review, not from German legislation. Legal status outside the US and Germany was not examined.

Read the original source
Systematic review: 11 trials (583 patients), 14 case reports (16 patients)

Systematic review and meta-analysis

Kupats E et al. Pharmacopsychiatry. 2020;53(5):201-208. PMID 32340063.

The review pooled 11 phenibut clinical trials (583 patients) and 14 case reports of dependence or intoxication (16 patients). Trial adverse events occurred in 5.66% of patients, the most common being somnolence (1.89%). In the case reports the doses were 0.5 to 100 g a day, with cardiovascular effects, insomnia, anxiety, agitation, hallucinations and depressed consciousness. The authors conclude phenibut is well tolerated at therapeutic doses and say the quality of online-bought product and the role of alcohol and other drugs remain open.

Participants / model
Patients in clinical trials and people in case reports
Treatment
Oral phenibut
Follow-up
Not stated in the source
Study design
Systematic review of 11 clinical trials and 14 case reports
Funding
not stated in the source

The abstract does not give the trial designs, and the authors are from Latvian institutions.

Read the original source
Phenibut leaflet: anxiety-neurotic and sleep uses, label wording on anxiety and sleep

Official label

Russian-language patient leaflet for Phenibut 250 mg tablets (phenibut hydrochloride), registration number LSR-002562/09 printed in Cyrillic letters. Copy hosted on medi.ru; version date not shown.

The leaflet lists asthenic and anxiety-neurotic states, stuttering, tics and bedwetting in children, insomnia and night anxiety in the elderly, Meniere disease and vestibular dizziness, motion-sickness prevention, and alcohol withdrawal as part of combined therapy. The pharmacodynamics section says the drug reduces anxiety and tension and normalizes sleep, without sedation or excitement. It lists drowsiness, nausea, irritability, agitation, anxiety, dizziness, headache and allergic reactions as side effects, names fatty liver degeneration, eosinophilia, low blood pressure and kidney impairment under overdose, and contraindicates pregnancy, breastfeeding and age under 3.

Participants / model
Adults and children over 3
Treatment
Phenibut hydrochloride 250 mg oral tablets
Follow-up
Version date not shown
Study design
Russian-language patient leaflet, copy hosted on a drug-information site
Funding
not stated in the source

These are label descriptions, not trial results. A Russian registration is not an FDA or EMA review. The copy was read on a commercial drug-information site, not on the Russian state register.

Read the original source

What happens in phenibut dependence and withdrawal?

Case-report reviews describe severe withdrawal. Among 25 published withdrawal cases, onset came as soon as 2 hours after the last dose, 11 patients (44%) were admitted to intensive care and 6 (24%) were intubated. No standard treatment exists.

A systematic review of 62 cases from 36 studies of phenibut toxicity or withdrawal found 86.8% obtained phenibut online and 63.2% used other addictive substances, mainly benzodiazepines and alcohol. 48.7% of toxicity cases were intubated. In withdrawal cases 95.7% reported daily use, and the common symptoms were anxiety, irritability or agitation, insomnia and psychosis. 69.6% of withdrawal cases needed more than one medication. Mean hospital stay was 5.0 days for toxicity and 7.7 days for withdrawal.

A second systematic review of phenibut withdrawal (515 articles screened, 25 included, all case reports or conference abstracts) found a typical pre-withdrawal dose of 10 g a day (interquartile range 4.75 to 21.5 g, range 1 to 200 g), with the shortest use before withdrawal being one week at 2 to 3 g a day. Withdrawal began as soon as 2 hours after the last dose, and 16 of 25 patients (64%) worsened in the first 24 hours of care. Seizures occurred in 2 (8%), intubation in 6 (24%) and intensive-care admission in 11 (44%). Only 3 patients (12%) were managed as outpatients, and withdrawal looked similar with phenibut alone or with other substances. There is no standard treatment.

Published cases are a biased sample of severe presentations and cannot give rates of harm among all users.

Case review: 62 cases, 48.7% of toxicity cases intubated

Case report

Weleff J et al. J Addict Med. 2023;17(4):407-417. PMID 37579098.

Of 62 cases from 36 studies, 86.8% obtained phenibut online and 63.2% used other addictive substances, mainly benzodiazepines and alcohol. 48.7% of toxicity cases were intubated. In withdrawal cases 95.7% reported daily use, and the common symptoms were anxiety, irritability or agitation, insomnia and psychosis. 69.6% of withdrawal cases needed more than one medication. Mean hospital stay was 5.0 days for toxicity and 7.7 days for withdrawal.

Participants / model
62 published cases, 80.7% male, mean age 30.9 years
Treatment
Phenibut, mostly bought online
Follow-up
Published cases
Study design
Systematic review of 62 case reports from 36 studies
Funding
not stated in the source

Case-report data carry publication bias and cannot give rates of harm among all users.

Read the original source
Withdrawal review: 25 cases, intensive care 44%, intubation 24%

Case report

Feldman R et al. Clin Toxicol (Phila). 2023;61(11):941-951. PMID 38112312.

Of 515 articles screened, 25 were included, all case reports or conference abstracts. A typical pre-withdrawal dose was 10 g a day (interquartile range 4.75 to 21.5 g, range 1 to 200 g), and the shortest use before withdrawal was one week at 2 to 3 g a day. Withdrawal began as soon as 2 hours after the last dose, and 16 of 25 patients (64%) worsened in the first 24 hours of care. Seizures occurred in 2 (8%), intubation in 6 (24%) and intensive-care admission in 11 (44%). Only 3 patients (12%) were managed as outpatients. Withdrawal looked similar with phenibut alone or with other substances. There is no standard treatment.

Participants / model
25 published cases
Treatment
Phenibut, mostly unregulated supplement
Follow-up
Published cases
Study design
Systematic review of case reports and conference abstracts
Funding
not stated in the source

Published cases are a biased sample of severe presentations.

Read the original source

Why does phenibut sit in F tier?

F grades phenibut as it is actually sold and used. The anxiety and sleep claim has no placebo-controlled trial behind it, while dependence, withdrawal that can begin within hours, US poison-center exposures with 3 deaths, and FDA's misbranding position are documented.

The anxiety and sleep claim rests on a Russian leaflet and on small, mostly uncontrolled or active-comparator Russian trials, with no placebo-controlled trial of either outcome found. The published downside is large: dependence with withdrawal beginning within hours, a withdrawal case series with 44% intensive-care admission and 24% intubation, 1,320 US poison-center exposures with 12.6% major effects and 3 deaths, illegal status in Germany according to a 2024 review, and FDA's position that supplements containing it are misbranded.

The grade covers phenibut as it is sold and used, including unregulated supplements, not only the Russian prescription tablet, where trial adverse events were 5.66%.

Phenibut leaflet: anxiety-neurotic and sleep uses, label wording on anxiety and sleep

Official label

Russian-language patient leaflet for Phenibut 250 mg tablets (phenibut hydrochloride), registration number LSR-002562/09 printed in Cyrillic letters. Copy hosted on medi.ru; version date not shown.

The leaflet lists asthenic and anxiety-neurotic states, stuttering, tics and bedwetting in children, insomnia and night anxiety in the elderly, Meniere disease and vestibular dizziness, motion-sickness prevention, and alcohol withdrawal as part of combined therapy. The pharmacodynamics section says the drug reduces anxiety and tension and normalizes sleep, without sedation or excitement. It lists drowsiness, nausea, irritability, agitation, anxiety, dizziness, headache and allergic reactions as side effects, names fatty liver degeneration, eosinophilia, low blood pressure and kidney impairment under overdose, and contraindicates pregnancy, breastfeeding and age under 3.

Participants / model
Adults and children over 3
Treatment
Phenibut hydrochloride 250 mg oral tablets
Follow-up
Version date not shown
Study design
Russian-language patient leaflet, copy hosted on a drug-information site
Funding
not stated in the source

These are label descriptions, not trial results. A Russian registration is not an FDA or EMA review. The copy was read on a commercial drug-information site, not on the Russian state register.

Read the original source
PubMed search, 10 October 2026: 9 records, none a placebo-controlled anxiety or sleep trial

PubMed search record

PubMed search run on 10 October 2026: (phenibut OR fenibut OR phenigam OR noofen) AND (randomized OR randomised OR placebo OR double-blind OR controlled OR open-label) AND (anxiety OR insomnia OR sleep OR neurosis OR asthenia OR stress OR patients). 9 records returned.

The search returned 9 records, and the abstract of each was read. None was a placebo-controlled trial of anxiety or sleep. The nearest were a randomized comparison in 62 patients with cerebrovascular disease and anxiety given phenibut hydrochloride (marketed as noophen, n = 33) or adaptol (n = 29) with no placebo, where anxiety symptoms stopped in 79.0% of patients across both groups and sleep disorders fell in the phenibut group (PMID 28300804); an open randomized trial in 50 children with ADHD versus multivitamins (PMID 25403296); a 30-adolescent comparison with adaptol (PMID 25726788); and a 30-patient uncontrolled series in tension headache (PMID 28805758). A 1997 study in volunteers under heat stress included a placebo arm, bemethyl 0.5 g and phenibut 0.25 g, but measured heat tolerance, not anxiety or sleep (PMID 9235216). The anxiety and sleep claim has no placebo-controlled human trial among these records.

Participants / model
Records returned, not a population
Treatment
Not applicable
Follow-up
Search run on 10 October 2026
Study design
Literature search
Funding
not stated in the source

A search result shows what PubMed returned on that date. It is not proof that no unindexed study exists. The 1997 heat study appears only as an abstract fragment.

Read the original source
Withdrawal review: 25 cases, intensive care 44%, intubation 24%

Case report

Feldman R et al. Clin Toxicol (Phila). 2023;61(11):941-951. PMID 38112312.

Of 515 articles screened, 25 were included, all case reports or conference abstracts. A typical pre-withdrawal dose was 10 g a day (interquartile range 4.75 to 21.5 g, range 1 to 200 g), and the shortest use before withdrawal was one week at 2 to 3 g a day. Withdrawal began as soon as 2 hours after the last dose, and 16 of 25 patients (64%) worsened in the first 24 hours of care. Seizures occurred in 2 (8%), intubation in 6 (24%) and intensive-care admission in 11 (44%). Only 3 patients (12%) were managed as outpatients. Withdrawal looked similar with phenibut alone or with other substances. There is no standard treatment.

Participants / model
25 published cases
Treatment
Phenibut, mostly unregulated supplement
Follow-up
Published cases
Study design
Systematic review of case reports and conference abstracts
Funding
not stated in the source

Published cases are a biased sample of severe presentations.

Read the original source
US poison centers: 1,320 exposure calls, major effects in 12.6%, 3 deaths

Human study

Graves JM et al. MMWR Morb Mortal Wkly Rep. 2020;69(35):1227-1228. PMID 32881852.

US poison centers received 1,320 phenibut exposure calls from 2009 to 2019, rising sharply after 2015. Of exposures, 58.4% were in adults aged 18 to 34, and 75.5% were in men. Reported effects included agitation (30.4%), drowsiness or lethargy (29.0%), tachycardia (21.9%) and confusion (21.3%). Coma occurred in 80 cases (6.2%). Major effects occurred in 12.6% of exposures, and 3 deaths were reported. Among exposures where phenibut was the only agent, 10.2% had major effects, including one death.

Participants / model
People exposed to phenibut, mostly adults aged 18 to 34
Treatment
Phenibut tablets (65.1%) or powder (24.8%) among known forms, mostly ingested
Follow-up
2009 to 2019
Study design
National surveillance report (MMWR)
Funding
not stated in the source

Exposure calls are not laboratory confirmed, and the report says the reason for the rise is not known.

Read the original source
German review: illegal in Germany; 17 poison-center inquiries, no respiratory depression or coma

Narrative review

Bonnet U et al. Dtsch Arztebl Int. 2024;121(7):222-227. PMID 38377332.

The review states phenibut is a prescription drug in Russia but that its production, possession, use, trafficking and administration are illegal in Germany. The regional poison center behind the review (GIZ-Nord) logged 17 phenibut inquiries from 2008 to 2022, with overdoses of 2 to 100 g in 15 of the 17, somnolence in 8, and no respiratory depression or coma, including after 100 g. The authors note no phenibut deaths had been published in Germany or elsewhere in Western Europe, and that such cases may have been overlooked.

Participants / model
Poison-center callers in northern Germany and published cases
Treatment
Phenibut taken orally, mostly as an unregulated supplement
Follow-up
Inquiries from 2008 to 2022
Study design
Narrative review with regional poison-center data
Funding
not stated in the source

Legal status was read from this review, not from German legislation. Legal status outside the US and Germany was not examined.

Read the original source
FDA: not a dietary ingredient; warning letters April 2019, injunction 2 June 2023

Regulatory record

U.S. Food and Drug Administration. Phenibut in Dietary Supplements, page current as of 12 July 2023.

FDA says phenibut does not meet the statutory definition of a dietary ingredient, so any supplement declaring it as a dietary ingredient is misbranded. The page records warning letters to three companies in April 2019 and a permanent injunction entered on 2 June 2023 against an individual doing business as Chill6, whose beverage powders contained phenibut HCl and were labeled to treat insomnia, alcoholism, PTSD and anxiety disorder.

Participants / model
Not a clinical population
Treatment
Dietary supplement products containing phenibut
Follow-up
Page current as of 12 July 2023
Study design
Official FDA record
Funding
not stated in the source

Later FDA actions were not examined.

Read the original source
Systematic review: 11 trials (583 patients), 14 case reports (16 patients)

Systematic review and meta-analysis

Kupats E et al. Pharmacopsychiatry. 2020;53(5):201-208. PMID 32340063.

The review pooled 11 phenibut clinical trials (583 patients) and 14 case reports of dependence or intoxication (16 patients). Trial adverse events occurred in 5.66% of patients, the most common being somnolence (1.89%). In the case reports the doses were 0.5 to 100 g a day, with cardiovascular effects, insomnia, anxiety, agitation, hallucinations and depressed consciousness. The authors conclude phenibut is well tolerated at therapeutic doses and say the quality of online-bought product and the role of alcohol and other drugs remain open.

Participants / model
Patients in clinical trials and people in case reports
Treatment
Oral phenibut
Follow-up
Not stated in the source
Study design
Systematic review of 11 clinical trials and 14 case reports
Funding
not stated in the source

The abstract does not give the trial designs, and the authors are from Latvian institutions.

Read the original source

Studies and sources

Phenibut leaflet: anxiety-neurotic and sleep uses, label wording on anxiety and sleep

Official label

Russian-language patient leaflet for Phenibut 250 mg tablets (phenibut hydrochloride), registration number LSR-002562/09 printed in Cyrillic letters. Copy hosted on medi.ru; version date not shown.

The leaflet lists asthenic and anxiety-neurotic states, stuttering, tics and bedwetting in children, insomnia and night anxiety in the elderly, Meniere disease and vestibular dizziness, motion-sickness prevention, and alcohol withdrawal as part of combined therapy. The pharmacodynamics section says the drug reduces anxiety and tension and normalizes sleep, without sedation or excitement. It lists drowsiness, nausea, irritability, agitation, anxiety, dizziness, headache and allergic reactions as side effects, names fatty liver degeneration, eosinophilia, low blood pressure and kidney impairment under overdose, and contraindicates pregnancy, breastfeeding and age under 3.

Participants / model
Adults and children over 3
Treatment
Phenibut hydrochloride 250 mg oral tablets
Follow-up
Version date not shown
Study design
Russian-language patient leaflet, copy hosted on a drug-information site
Funding
not stated in the source

These are label descriptions, not trial results. A Russian registration is not an FDA or EMA review. The copy was read on a commercial drug-information site, not on the Russian state register.

Read the original source
FDA: not a dietary ingredient; warning letters April 2019, injunction 2 June 2023

Regulatory record

U.S. Food and Drug Administration. Phenibut in Dietary Supplements, page current as of 12 July 2023.

FDA says phenibut does not meet the statutory definition of a dietary ingredient, so any supplement declaring it as a dietary ingredient is misbranded. The page records warning letters to three companies in April 2019 and a permanent injunction entered on 2 June 2023 against an individual doing business as Chill6, whose beverage powders contained phenibut HCl and were labeled to treat insomnia, alcoholism, PTSD and anxiety disorder.

Participants / model
Not a clinical population
Treatment
Dietary supplement products containing phenibut
Follow-up
Page current as of 12 July 2023
Study design
Official FDA record
Funding
not stated in the source

Later FDA actions were not examined.

Read the original source
German review: illegal in Germany; 17 poison-center inquiries, no respiratory depression or coma

Narrative review

Bonnet U et al. Dtsch Arztebl Int. 2024;121(7):222-227. PMID 38377332.

The review states phenibut is a prescription drug in Russia but that its production, possession, use, trafficking and administration are illegal in Germany. The regional poison center behind the review (GIZ-Nord) logged 17 phenibut inquiries from 2008 to 2022, with overdoses of 2 to 100 g in 15 of the 17, somnolence in 8, and no respiratory depression or coma, including after 100 g. The authors note no phenibut deaths had been published in Germany or elsewhere in Western Europe, and that such cases may have been overlooked.

Participants / model
Poison-center callers in northern Germany and published cases
Treatment
Phenibut taken orally, mostly as an unregulated supplement
Follow-up
Inquiries from 2008 to 2022
Study design
Narrative review with regional poison-center data
Funding
not stated in the source

Legal status was read from this review, not from German legislation. Legal status outside the US and Germany was not examined.

Read the original source
Systematic review: 11 trials (583 patients), 14 case reports (16 patients)

Systematic review and meta-analysis

Kupats E et al. Pharmacopsychiatry. 2020;53(5):201-208. PMID 32340063.

The review pooled 11 phenibut clinical trials (583 patients) and 14 case reports of dependence or intoxication (16 patients). Trial adverse events occurred in 5.66% of patients, the most common being somnolence (1.89%). In the case reports the doses were 0.5 to 100 g a day, with cardiovascular effects, insomnia, anxiety, agitation, hallucinations and depressed consciousness. The authors conclude phenibut is well tolerated at therapeutic doses and say the quality of online-bought product and the role of alcohol and other drugs remain open.

Participants / model
Patients in clinical trials and people in case reports
Treatment
Oral phenibut
Follow-up
Not stated in the source
Study design
Systematic review of 11 clinical trials and 14 case reports
Funding
not stated in the source

The abstract does not give the trial designs, and the authors are from Latvian institutions.

Read the original source
Rodent and in vitro: GABA-B affinity 177 micromolar racemic, 92 R-phenibut, 6.0 baclofen

Animal study

Dambrova M et al. Eur J Pharmacol. 2008;583(1):128-34. PMID 18275958.

In GABA-B receptor binding experiments and rodent tests, racemic phenibut bound the receptor with an affinity constant of 177 micromolar, R-phenibut 92 micromolar and baclofen 6.0 micromolar, and S-phenibut was inactive, so the activity of the racemic drug comes from R-phenibut. A second paper (PMID 26234470) found R-phenibut also binds the alpha2-delta subunit of voltage-dependent calcium channels (Ki 23 micromolar versus 0.05 micromolar for gabapentin) in rat brain membranes.

Participants / model
Rats and mice, with in vitro receptor binding
Treatment
Phenibut isomers and baclofen in assays and rodent tests; route and dose not stated in the source
Follow-up
Not stated in the source
Study design
Original animal and in vitro study
Funding
not stated in the source

This supports the baclofen and gabapentinoid relationship but is animal and in vitro work and says nothing about anxiety or sleep in people. Endpoints were GABA-B binding affinity and locomotor, antidepressant and pain tests.

Read the original source
US poison centers: 1,320 exposure calls, major effects in 12.6%, 3 deaths

Human study

Graves JM et al. MMWR Morb Mortal Wkly Rep. 2020;69(35):1227-1228. PMID 32881852.

US poison centers received 1,320 phenibut exposure calls from 2009 to 2019, rising sharply after 2015. Of exposures, 58.4% were in adults aged 18 to 34, and 75.5% were in men. Reported effects included agitation (30.4%), drowsiness or lethargy (29.0%), tachycardia (21.9%) and confusion (21.3%). Coma occurred in 80 cases (6.2%). Major effects occurred in 12.6% of exposures, and 3 deaths were reported. Among exposures where phenibut was the only agent, 10.2% had major effects, including one death.

Participants / model
People exposed to phenibut, mostly adults aged 18 to 34
Treatment
Phenibut tablets (65.1%) or powder (24.8%) among known forms, mostly ingested
Follow-up
2009 to 2019
Study design
National surveillance report (MMWR)
Funding
not stated in the source

Exposure calls are not laboratory confirmed, and the report says the reason for the rise is not known.

Read the original source
Case review: 62 cases, 48.7% of toxicity cases intubated

Case report

Weleff J et al. J Addict Med. 2023;17(4):407-417. PMID 37579098.

Of 62 cases from 36 studies, 86.8% obtained phenibut online and 63.2% used other addictive substances, mainly benzodiazepines and alcohol. 48.7% of toxicity cases were intubated. In withdrawal cases 95.7% reported daily use, and the common symptoms were anxiety, irritability or agitation, insomnia and psychosis. 69.6% of withdrawal cases needed more than one medication. Mean hospital stay was 5.0 days for toxicity and 7.7 days for withdrawal.

Participants / model
62 published cases, 80.7% male, mean age 30.9 years
Treatment
Phenibut, mostly bought online
Follow-up
Published cases
Study design
Systematic review of 62 case reports from 36 studies
Funding
not stated in the source

Case-report data carry publication bias and cannot give rates of harm among all users.

Read the original source
Withdrawal review: 25 cases, intensive care 44%, intubation 24%

Case report

Feldman R et al. Clin Toxicol (Phila). 2023;61(11):941-951. PMID 38112312.

Of 515 articles screened, 25 were included, all case reports or conference abstracts. A typical pre-withdrawal dose was 10 g a day (interquartile range 4.75 to 21.5 g, range 1 to 200 g), and the shortest use before withdrawal was one week at 2 to 3 g a day. Withdrawal began as soon as 2 hours after the last dose, and 16 of 25 patients (64%) worsened in the first 24 hours of care. Seizures occurred in 2 (8%), intubation in 6 (24%) and intensive-care admission in 11 (44%). Only 3 patients (12%) were managed as outpatients. Withdrawal looked similar with phenibut alone or with other substances. There is no standard treatment.

Participants / model
25 published cases
Treatment
Phenibut, mostly unregulated supplement
Follow-up
Published cases
Study design
Systematic review of case reports and conference abstracts
Funding
not stated in the source

Published cases are a biased sample of severe presentations.

Read the original source
4 supplement brands: 21 to 1,164 mg per serving after the FDA warnings

Analytical product survey

Cohen PA et al. Clin Toxicol (Phila). 2022;60(4):486-488. PMID 34550038.

In 4 phenibut dietary-supplement brands tested before and after FDA warnings, 2 of 4 contained phenibut before (484 and 487 mg per serving), and all 4 contained it afterward, at 21 to 1,164 mg per serving. Two brands showed phenibut only after the warnings, and the amount rose in 3 of the 4 products. The highest amount was up to 450% above a typical Russian pharmaceutical tablet.

Participants / model
4 commercial supplement brands
Treatment
Dietary supplements, mixed forms
Follow-up
Before and after FDA warnings
Study design
Analytical product survey
Funding
not stated in the source

A very small sample, but it shows supplement content can be higher and less predictable than the prescription product. A product analysis, not a study in people.

Read the original source
PubChem: phenibut base, hydrochloride and baclofen identity

Chemical identity record

National Library of Medicine. PubChem compound records CID 14113 (phenibut), CID 11499499 (phenibut hydrochloride) and CID 2284 (baclofen).

Phenibut (4-amino-3-phenylbutanoic acid, beta-phenyl-GABA): PubChem CID 14113, C10H13NO2, 179.22 g/mol, CAS 1078-21-3. The hydrochloride, which is what the Russian tablets and most trials used: CID 11499499, C10H14ClNO2, 215.67 g/mol, CAS 3060-41-1. The drug is a racemate and R-phenibut carries the receptor activity. Baclofen: CID 2284, C10H12ClNO2, 213.66 g/mol, CAS 1134-47-0. Baclofen is the 4-chlorophenyl derivative of phenibut.

Participants / model
Chemical identity, not a clinical population
Treatment
Defined free base, hydrochloride salt and racemate
Follow-up
Not applicable
Study design
NLM chemical record
Funding
not stated in the source

A vendor phenibut may be the free base or the hydrochloride, which differ in molecular weight by about 20%. Identity record only; it says nothing about efficacy or safety.

Read the original source

Why is Phenibut in F tier?

F fits the way phenibut is actually sold and used. The anxiety and sleep claim rests on a Russian leaflet and small, mostly uncontrolled or active-comparator Russian trials, with no placebo-controlled trial found, while dependence, withdrawal that begins within hours, poison-center exposures and FDA's misbranding position are well documented. The grade covers phenibut as sold and used, not only the Russian prescription tablet, where trial adverse events were 5.66%.