Substance evidence
Phenibut
Dependence and withdrawal, from the case record.
What Its Legal Status Actually Means
Read this before anything below it. Legal to sell is not the same fact as reviewed, verified, or approved.
Phenibut has never been approved by the FDA for any medical use in the United States and is not a lawful dietary supplement ingredient: the FDA has stated that phenibut does not meet the statutory definition of a dietary ingredient, that products listing it as one are misbranded, and it issued warning letters in April 2019 to Evol Nutrition (Sleep Walker, Red Dawn Liquid), NeuroScience Solutions (Kavinace), and Atomixx (Limitless), with further letters since. It is nevertheless not scheduled under the federal Controlled Substances Act and is legal to possess, so it continues to be sold online as a "nootropic," "GABA supplement," or relaxation product with no content standards. It is a registered prescription medicine in Russia, Latvia, and neighbouring post-Soviet countries (brands Noofen, Anvifen, Fenibut), where typical tablets are 250 mg. Australia scheduled it as a Schedule 9 prohibited substance under the Poisons Standard in February 2018 after adolescent overdoses, banning manufacture, sale, and possession.
Quoted whole from the 2026-08-18 study harvest. Not summarized, not shortened.
What the Research Shows
5 records from the 2026-08-18 harvest, each checked against PubMed and Europe PMC on that date. How a study was designed, how many people were in it, and who paid for it are printed above what it found, because those three facts decide how much the finding is worth.
Study 1 · 2023
- Systematic review of observational studies
- 62 participants
- Reputable journal
- Funding not established
- Declared conflicts of interest
moderate60/100Reasonable evidence with real limitations.
Read this first: This is a systematic review of case reports, not of trials. Case reports capture only the people who reached a hospital and were written up, so they show what phenibut can do but cannot tell you how often it does it.
A systematic search of Medline, Embase, and the Cochrane Library found 62 published cases of phenibut toxicity or withdrawal across 36 reports and no controlled trials at all. Nearly half of the toxicity cases (48.7%) required intubation, the most common presentations were altered mental status, somnolence, psychosis, and movement disorders, and 95.7% of the withdrawal cases involved daily use; average hospital stays were 5.0 days for toxicity and 7.7 days for withdrawal, and about 87% of people had bought the drug online.
How this record was checked
PubMed record 37579098 fetched via NCBI efetch 2026-08-18; title, authors, journal, year, DOI, and the figures of 62 cases from 36 studies confirmed from the abstract. The PubMed record carries the conflict-of-interest statement "The authors report no conflicts of interest." Europe PMC core record checked 2026-08-18: no grant or funding statement available, so funding recorded UNKNOWN.
Study 2 · 2023
- Systematic review of observational studies
- 25 participants
- Reputable journal
- Funding not established
early signal54/100Suggestive but preliminary. Not settled.
Read this first: The authors state plainly that the whole data set is case reports and is therefore subject to publication bias, that reported doses may not reflect what unregulated products actually contained, and that people describing single-substance use may have been using other drugs too.
A PRISMA systematic review screened 515 articles and found 25 usable published phenibut withdrawal cases — all case reports or conference abstracts, no controlled studies. The shortest use before withdrawal was one week at 2-3 g/day, the median daily dose was 10 g, withdrawal began as soon as two hours after the last dose, 64% worsened within 24 hours of reaching care, 24% were intubated, 44% went to the ICU, and 76% needed at least two drugs to control symptoms. Every abrupt-cessation case was admitted as an inpatient.
How this record was checked
PubMed record 38112312 fetched via NCBI efetch 2026-08-18; title, all eight authors, journal, year, DOI, and the figures of 515 screened / 25 included cases confirmed from the abstract. Europe PMC core record checked 2026-08-18: no grant or funding statement available and no conflict-of-interest statement in the record, so funding recorded UNKNOWN and conflicts false.
Study 3 · 2020
- Cross-sectional study
- 1,320 participants
- Government body
- Funding not established
- Declared conflicts of interest
moderate56/100Reasonable evidence with real limitations.
Read this first: Poison-centre data are passive surveillance: exposures are self-reported by callers, are not laboratory-confirmed (phenibut is not detected on routine urine drug screens), and most people who use phenibut never call, so these numbers are a floor, not an incidence rate. Some of the rise after 2015 reflects "phenibut" being added as a searchable term that year.
CDC analysis of the National Poison Data System found 1,320 phenibut exposure calls from all 50 states between 2009 and 2019, rising sharply after 2015; 85% came from healthcare facilities and 75.5% involved men, mostly aged 18-34. Coma was reported in 80 cases (6.2%), major effects — life-threatening or causing significant disability — in 12.6%, and three people died; among cases where phenibut was the only substance involved, 10.2% still had major effects and one died.
How this record was checked
PubMed record 32881852 fetched via NCBI efetch 2026-08-18; title, authors, journal, year, and DOI confirmed. Full text fetched from Europe PMC (PMC7470459) 2026-08-18: N=1,320 exposures, 85.0% healthcare-facility calls, 6.2% coma, 12.6% major effects, three deaths, and 10.2% major effects in single-substance cases all read directly off the article; the record is flagged is-retracted: no. The article carries an ICMJE conflict-of-interest disclosure (none disclosed) but no funding statement, so funding recorded UNKNOWN.
Study 4 · 2019
- Case series
- 56 participants
- Reputable journal
- Funding not established
contested39/100Weak or heavily disputed. Treat as a question, not an answer.
Read this first: A single-state case series of 56 calls, with coingestants documented in 36% of patients, cannot separate phenibut's effects from other drugs and cannot estimate how common these outcomes are among people who use phenibut. It scores low on the evidence rubric by design — it is a description of hospital cases, not a study of whether phenibut helps or harms.
The Minnesota Poison Control System logged 56 phenibut exposure calls over 19 years, but 48 of them (85.7%) came in the last five years of that span. Over half of patients had central nervous system effects and 11 (19.6%) required intubation for respiratory failure; 23% said they were using phenibut to treat anxiety and 48% were classified as abuse. No deaths occurred in this series.
How this record was checked
PubMed record 30878413 fetched via NCBI efetch 2026-08-18; title, authors, journal, year, DOI, and the figures N=56, 85.7% in five years, 19.6% intubated, 48% abuse, 23% anxiety confirmed from the abstract. Europe PMC core record checked 2026-08-18: no grant or funding statement and no conflict-of-interest statement available, so funding recorded UNKNOWN and conflicts false.
Study 5 · 2022
- Cross-sectional study
- 4 participants
- Reputable journal
- Funding not established
early signal42/100Suggestive but preliminary. Not settled.
Read this first: Only four brands met the inclusion criteria, so this is a small snapshot rather than a market-wide survey; it demonstrates that labelled dose cannot be trusted, not the exact proportion of products that are mislabelled.
Researchers bought four brands of supplements labelled as containing phenibut before and after the FDA's 2019 warnings and analysed them by mass spectrometry. Before the warnings only two of four actually contained phenibut; afterwards all four did, at 21 mg to 1,164 mg per serving — up to 450% more than a 250 mg Russian pharmaceutical tablet — and the quantity had increased in three of the four products.
How this record was checked
PubMed record 34550038 fetched via NCBI efetch 2026-08-18; title, authors, journal, year, DOI, and the dose figures (484/487 mg before; 21-1,164 mg after; up to 450% of a 250 mg tablet) confirmed from the abstract. Europe PMC core record checked 2026-08-18: no grant or funding statement and no conflict-of-interest statement available, so funding recorded UNKNOWN and conflicts false.
The Risks
Nobody checks this purchase the way a prescription is checked. No prescriber reviews it against the rest of what you take, no pharmacist screens the interaction, and no regulator confirms the dose in the capsule before it is sold. That is why this section sits here at full length rather than as a footnote.
What the paragraph below covers:
- Slowed breathing
- Psychosis and mania
- Dependence and withdrawal
- Drug interactions
- What is actually in the product
- Sedation
Phenibut is a GABA-B receptor agonist, pharmacologically closer to baclofen and GHB than to any supplement, and it produces tolerance and physical dependence fast: in the published withdrawal literature the shortest documented time to withdrawal was one week of use at 2-3 g per day, and the median daily dose people had escalated to before withdrawal was 10 g — forty times a Russian pharmaceutical tablet. Withdrawal is not mild. Published cases include delirium, hallucinations, psychosis, severe agitation, seizures, intubation in about a quarter of cases, and ICU admission in about 44 percent; every published case of abrupt cessation was managed as an inpatient, most needed two or more drugs to control symptoms, and there is no standard treatment protocol. In overdose, phenibut causes profound sedation and respiratory depression; roughly one in five people in a regional poison-centre series required intubation, and US poison centres logged three deaths among 1,320 exposures over 2009-2019. Because it is not detected on routine urine drug screens and no commercial assay exists, emergency clinicians frequently cannot confirm it. Products sold online have been found to contain anywhere from 21 mg to 1,164 mg per serving, so users routinely do not know their dose. Combining phenibut with alcohol, benzodiazepines, opioids, or other sedatives compounds respiratory depression, and there is no controlled-trial evidence that it safely or effectively treats anxiety, insomnia, or any other mental health condition.
What Is Not Known
The boundaries of the section above, in the harvest’s own words. What it excluded, why, and where it looked and found nothing. An absence of evidence is not evidence of absence, and it is not evidence of benefit either.
What Was Left Out, and Why
Quoted from the harvest, where these notes sat above the study list rather than after it. Where a note says “below” it means the studies in the section above.
- No meta-analysis or systematic review of RCTs exists for phenibut in any Western indication. A PubMed search for phenibut AND (randomized OR randomised OR clinical trial) run 2026-08-18 returned 12 records; the only ones describing controlled human treatment studies are Russian-language papers in Zh Nevrol Psikhiatr Im S S Korsakova (e.g. PMIDs 29265084, 28805758, 27029450, 25591517) that were not obtainable in full text, are not placebo-controlled reports of anxiety or depression outcomes, and could not be verified end-to-end. They are therefore dropped, not guessed at. The complete absence of quality controlled efficacy evidence is the finding here.
- Individual phenibut case reports (BMJ Case Rep 23391959, Case Rep Psychiatry 29854531, WMJ 35442585, Pediatr Neonatol 35927183, and roughly 30 others) excluded in favour of the two systematic reviews below, which subsume them.
- Owen 2016 (Drug Alcohol Rev, PMID 26693960, internet-availability snapshot) excluded as a grey-literature survey superseded by the poison-centre data included here.
The Retraction Check
PubMed efetch records for all five PMIDs fetched 2026-08-18 and inspected for "Retraction in", "Erratum", "Expression of concern", and "Withdrawn" flags; none present. Europe PMC core records show no correction/retraction entries.
Questions for a Prescriber or Pharmacist
This page does not tell anyone to take Phenibut or to avoid it. It is not able to: it does not know what else you take, what you have tried, or what you are treating. These are the questions each study above raises, written to be asked out loud.
- I've been taking phenibut I bought online — given that the entire medical literature on it is emergency cases and not trials, how do we get me off it safely and what would we treat my anxiety or sleep with instead?
- If I stop phenibut suddenly, published cases show people needing intensive care — can we plan a supervised taper rather than my stopping on my own?
- Phenibut sends people to US poison centres more than a hundred times a year and has been linked to deaths even when taken alone — is there any reason for me to keep taking it instead of a treatment you can monitor?
- About a quarter of the people in this poison-centre series were taking phenibut for anxiety and one in five needed a breathing tube — what proven anxiety treatment could I use instead?
- Lab testing found phenibut supplements containing anywhere from 21 mg to over 1,100 mg per serving with no way to tell from the label — how would either of us know what dose I've actually been taking?
And the one to ask at the counter, whatever the answers above turn out to be: given everything I am already taking, what would you want to know about Phenibut before I put it in the same body?
Where This Page Comes From
Transcribed from the study-harvest-2026-08-18 record for phenibut, built into this page by scripts/supplement-ingest.mjs on 2026-09-07. Nothing here is fetched at page load, and nothing here was written by a model without a citation behind it.
| Source file | study-harvest/2026-08-18/phenibut.yaml |
|---|---|
| Source repo | REPTechnologies/avalo-backend |
| SHA-256 | fbed38121b164a2e3f9bf018225c26d318a3d2f196ed37a0c000f6079337260c |
| Also searched as | Noofen, Anvifen, Fenibut, beta-phenyl-GABA, 4-amino-3-phenylbutyric acid, phenygam |
The Other Substances
- 5-HTP
- Ashwagandha
- Cannabidiol (CBD)
- Cannabis and THC
- Creatine
- Kratom
- L-Theanine
- Magnesium
- Melatonin
- Methylene Blue
- Microdosing
- N-Acetylcysteine (NAC)
- Omega-3
- SAMe
- St John’s Wort
- Valerian
Do any supplements actually work? asks the question across all of them. The full library has the medication records, the funding investigations, and the glossary.