Phenibut is a GABA derivative developed in the USSR and used in Russia and neighbouring countries since the 1960s as a prescription anxiolytic. It acts mainly at GABA-B receptors, like baclofen, and its R-enantiomer also binds the gabapentinoid alpha-2-delta site. Trials, mostly Russian, report few side effects at clinical doses. Western users buy it online and often take far more, and case series and poison-centre data show dependence, severe withdrawal, intensive-care admissions and seizures. The cognitive evidence is thin. It is not approved in the US, and Australia lists it in Schedule 9.
Summary drafted from this entry’s sources; editorial review pending.
01Key questions
How does phenibut work?
It is a GABA-B receptor agonist, related to baclofen, and its R-enantiomer also binds the alpha-2-delta subunit of voltage-gated calcium channels, the target of gabapentin and pregabalin, with about four times greater affinity than it has for GABA-B in rat brain.12
Is phenibut a nootropic?
Its developers called it one, and old Soviet and Russian studies report effects on anxiety, sleep and asthenia. There are no modern placebo-controlled trials of cognition in healthy people. The anxiolytic and sedative effects are better supported than any cognitive one.13
Is phenibut addictive?
Yes. A 2023 systematic review of withdrawal reports found that 44% of patients needed intensive care, and US poison-centre exposures rose sharply after 2015. Tolerance and withdrawal can appear after a week of regular use at gram amounts.54
Is phenibut legal?
It is a prescription drug in Russia. In the US the FDA says it does not meet the legal definition of a dietary ingredient, so supplements declaring it are misbranded. Australia lists it in Schedule 9, its prohibited-substance category.8
What would change this rating?
Modern placebo-controlled trials with cognitive outcomes and long-term dependence monitoring. Given the withdrawal record, safety data would matter more than any efficacy signal.
Phenibut is a Soviet drug from the 1960s, a GABA molecule with a phenyl ring added so it crosses into the brain. In Russia and neighbouring countries it is a prescription anxiolytic with half a century of clinical use and a mild side-effect record in trials. In the West it is sold online as a "nootropic" powder, where people often take far more than the amounts used clinically, and the result is a documented pattern of dependence, severe withdrawal and intensive-care admissions. The cognitive evidence is thin; the anxiolytic and sedative effects are real; the dependence risk is the most important fact about it.
02What it is
Phenibut (beta-phenyl-gamma-aminobutyric acid) was developed in the USSR and introduced into Russian clinical practice in the 1960s. It is close kin to baclofen, which is phenibut with a chlorine atom added. Russian doctors use it for tension, anxiety and fear, insomnia, before and after surgery, and for asthenia, post-traumatic stress, stuttering and vestibular disorders (Lapin, 2001, PMID 11830761). It sits alongside bromantane, Noopept and the peptide drugs in the Russian pharmacology tradition, but pharmacologically it is a sedative, not a stimulant or a memory drug.
03How it works
- GABA-B agonist. Its main action is at GABA-B receptors, with some GABA-A activity; it was also reported to affect dopamine signalling (PMID 11830761).
- Gabapentin-like binding. The active R-enantiomer binds the alpha-2-delta subunit of voltage-gated calcium channels, the target of gabapentin and pregabalin, with about four times higher affinity than it binds GABA-B receptors (dissociation constant about 23 µM). Its pain-relieving effect in rats ran through this site, not GABA-B (Zvejniece et al., 2015, PMID 26234470).
Two sedative mechanisms that both produce tolerance and withdrawal explain the clinical story better than the "nootropic" label does.
04The clinical record
A 2020 systematic review from a Latvian group that also studies phenibut in the lab pooled 11 clinical trials with 583 patients. Adverse events were reported in 5.7% of patients, mostly drowsiness (1.9%). The same review gathered 14 case reports of dependence or intoxication in which reported intakes started inside the clinical range and reached many times above it (Kupats et al., 2020, PMID 32340063).
That gap is the whole story. At prescription doses, in supervised courses, phenibut looks like a mild anxiolytic. Bought online and dosed by feel, it becomes something else. Most of the clinical trials are older Russian-language studies, and none tested cognitive enhancement in healthy people.
05Western use: dependence and withdrawal
- US poison centers, 2009 to 2019: 1,320 phenibut exposures, rising sharply after 2015; three quarters were men and most were aged 18 to 34. Drowsiness, agitation, fast heart rate and confusion were common; 6.2% involved coma, 12.6% had major (life-threatening or disabling) effects, and three people died (Graves et al., 2020, PMID 32881852).
- Withdrawal: a 2023 systematic review of 25 withdrawal reports found a median daily intake about five times the top of the usual clinical range. Withdrawal could begin two hours after the last dose and appeared after as little as one week of regular use. 44% of patients went to intensive care, 24% were intubated and 8% had seizures. Withdrawal was just as severe in people who used phenibut alone as in those who used other drugs too (Feldman et al., 2023, PMID 38112312).
- Toxicity and withdrawal together: another review of 62 cases found that 87% bought phenibut online. Toxicity brought altered consciousness, sleepiness, psychosis and movement disorders, and about half of those patients were intubated. Withdrawal brought anxiety, agitation, insomnia and psychosis, and most cases needed several drugs to control, typically benzodiazepines, baclofen, antipsychotics, gabapentinoids or barbiturates (Weleff et al., 2023, PMID 37579098).
- Products: online phenibut capsules held more or less phenibut than labelled and included undeclared ingredients (Upmanis et al., 2024, PMID 39459348). It also turns up, sometimes undeclared, in US "cognitive" supplements (PMID 34484905), and alongside tianeptine in poison-center calls (PMID 30070980).
06Legal status
| Where | Status |
|---|---|
| Russia and parts of Eastern Europe | Registered prescription medicine (PMID 39459348; PMID 32340063) |
| United States | Not approved and not federally scheduled. The FDA says phenibut does not meet the legal definition of a dietary ingredient, so supplements declaring it are misbranded. It sent three warning letters in April 2019, and a federal court ordered a permanent injunction against the "Chill6" beverage seller in 2023 (FDA) |
| Australia | Schedule 9, prohibited substance, since February 2018, under a scheduling decision published in October 2017 that cited dependence, withdrawal and overdose (TGA) |
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07Claims audit
| Claim | Verdict | Why |
|---|---|---|
| "A nootropic" | Weak | Russian sources describe cognitive benefits, but there are no modern trials of cognition, and its actions are sedative |
| "Safe, used in Russia for 50 years" | Partly true | Trials report few side effects at clinical doses, but they were short and did not look for dependence, and no dependence-free threshold has been established. Withdrawal case reports cluster at higher intakes |
| "Not addictive" | False | Withdrawal after one week of daily use, ICU care in 44% of reported withdrawal cases |
| "A dietary supplement" | False in the US | The FDA says it is not a dietary ingredient |
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08What would change the rating
Modern, placebo-controlled trials of phenibut for anxiety or cognition at clinical doses, with tolerance and withdrawal measured, would let it be rated on evidence rather than history. Better withdrawal management data would matter more to the people already using it.
09Where to get it
The FDA says phenibut is not a dietary ingredient, and online powders drive the dependence cases. We don't link to sellers, affiliate or otherwise. How we make money
What studies and practitioners report
Amounts as reported in the cited sources: trial doses with the population studied, and practitioner-reported ranges marked as such. Not medical advice.
- Practitioner-reported 0.25-2 g/day · Usual clinical range in Eastern European use patients treated with phenibut in clinical practice and trials (systematic review) PMID 32340063
Further reading: detailed protocols
- FDA: phenibut in dietary supplements fda.gov
- PsychonautWiki: Phenibut (community wiki) psychonautwiki.org
10Connections
11Sources
- Lapin I. Phenibut (beta-phenyl-GABA): a tranquilizer and nootropic drug. CNS Drug Rev. 2001;7(4):471-81. PMID 11830761PubMed 11830761
- Zvejniece L, Vavers E, Svalbe B et al. R-phenibut binds to the α2-δ subunit of voltage-dependent calcium channels and exerts gabapentin-like anti-nociceptive effects. Pharmacol Biochem Behav. 2015;137:23-9. PMID 26234470PubMed 26234470
- 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;53(5):201-208. PMID 32340063PubMed 32340063
- Graves JM, Dilley J, Kubsad S, Liebelt E. Notes from the field: phenibut exposures reported to poison centers, United States, 2009-2019. MMWR. 2020;69(35):1227-1228. PMID 32881852PubMed 32881852
- 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. Clin Toxicol. 2023;61(11):941-951. PMID 38112312PubMed 38112312
- Weleff J, Kovacevich A, Burson J et al. Clinical presentations and treatment of phenibut toxicity and withdrawal: a systematic literature review. J Addict Med. 2023;17(4):407-417. PMID 37579098PubMed 37579098
- Upmanis T, Sevostjanovs E, Zvejniece L et al. Purchasing "nootropics" online: identification and quantification of ingredients in phenibut-containing products. Medicina. 2024;60(10):1561. PMID 39459348PubMed 39459348
- Cohen PA, Avula B, Wang YH et al. Five unapproved drugs found in cognitive enhancement supplements. Neurol Clin Pract. 2021;11(3):e303-e307. PMID 34484905PubMed 34484905
- El Zahran T et al. Characteristics of tianeptine exposures reported to the National Poison Data System, 2000-2017. MMWR. 2018;67(30):815-818. PMID 30070980PubMed 30070980
12Entry history
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Heretic informs and never prescribes. Where amounts appear, they describe what published studies used. Talk to a qualified clinician before acting on anything here.