Phenibut
A GABA-B receptor agonist developed and approved in the 1960s in the Soviet Union as a short-course prescription anxiolytic. NOT FDA-approved in the United States — the FDA has explicitly stated phenibut does not qualify as a dietary supplement ingredient. Real risks include rapid tolerance, severe physical dependence, and a life-threatening withdrawal syndrome resembling benzodiazepine or GHB withdrawal. ED case reports have risen sharply since online sale began.
Research compound — not an approved drug or dietary supplement
This compound is sold for research and is not FDA-approved for human use or as a dietary supplement. Human evidence is limited; purity and dosing of consumer products are unverified. The data below is an evidence review for education only — talk to a clinician before considering it.
Quick decision guide
May help most
No FDA-approved indication. In Russia/Ukraine/Latvia, prescribed short-term (2–3 weeks) for anxiety, insomnia, or pediatric tics under medical supervision. Self-administered chronic use carries serious dependence and withdrawal risks.
Common dosing range
Russian prescribing: 250–500 mg up to three times daily for short courses (max 2–3 weeks). Recreational and self-treatment doses online are often much higher and chronic — these are the cases that show up in poison control data.
When to expect effects
Single dose: 2–4 hours for anxiolytic effect; tolerance develops within days to weeks of regular use.
Watch out for
Severe withdrawal syndrome (seizures, psychosis, autonomic instability) on cessation of regular use. Multiple deaths and ICU admissions reported. The FDA has issued warning letters against phenibut as a 'supplement'.
Evidence snapshot
What is it
Phenibut (beta-phenyl-gamma-aminobutyric acid) is a synthetic GABA analog developed in the Soviet Union in the 1960s as a prescription medication for anxiety, insomnia, and other conditions. It is not approved as a medication in the United States or most Western countries, but it is sold in some places as a dietary supplement.
Is it worth it for you?
Use this as a quick fit check, not a diagnosis.
Probably skip if…
Evidence at a glance
| Goal | Effect | Best fit | Time |
|---|---|---|---|
Acute anxiolysis (single short-term dose) Mixed Evidence | Subjective anxiolysis at 2–4 hours after 250–500 mg in older Russian clinical reports; no modern English-language RCTs | Single short-term use in a clinically supervised setting (the original Russian indication) | 2–4 hours from a single dose |
Sleep / insomnia Mixed Evidence | Sedation and reduced sleep latency at 250–500 mg evening dose in Soviet-era case series; tolerance within days–weeks | Not appropriate for ongoing insomnia management because of dependence risk | 1–3 hours from dose |
Cognitive enhancement / nootropic claims Weak Evidence | No controlled human evidence of cognitive enhancement | None | Not applicable |
Acute anxiolysis (single short-term dose)
- Effect
- Subjective anxiolysis at 2–4 hours after 250–500 mg in older Russian clinical reports; no modern English-language RCTs
- Best fit
- Single short-term use in a clinically supervised setting (the original Russian indication)
- Time
- 2–4 hours from a single dose
Sleep / insomnia
- Effect
- Sedation and reduced sleep latency at 250–500 mg evening dose in Soviet-era case series; tolerance within days–weeks
- Best fit
- Not appropriate for ongoing insomnia management because of dependence risk
- Time
- 1–3 hours from dose
Cognitive enhancement / nootropic claims
- Effect
- No controlled human evidence of cognitive enhancement
- Best fit
- None
- Time
- Not applicable
Evidence for 3 uses
AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.
Acute anxiolysis (single short-term dose)
Supplement benefitPhenibut is a GABA-B agonist with weaker GABA-A activity. The acute anxiolytic effect after a single 250–500 mg dose is real and is the basis for its original Soviet clinical approval. Russian-language clinical literature dating to the 1970s reports benefit in generalized anxiety, social anxiety, and pre-procedural stress. However: (1) there are no modern English-language RCTs that meet current methodological standards, (2) tolerance to the anxiolytic effect develops rapidly with repeat dosing, and (3) the same GABA-B mechanism that produces anxiolysis is responsible for dependence and withdrawal.
Bottom line: Real pharmacology, real anxiolysis, but the same mechanism makes it a dependence-prone drug. Don't use chronically; if used at all, single occasional doses only.
Sleep / insomnia
Supplement benefitSedation is a class effect of GABA-B agonism. Phenibut at 250–500 mg taken in the evening produces sedation and shortened sleep latency in older Russian clinical reports. No modern English-language RCTs exist. Daily use for sleep produces tolerance within days to weeks; this is the most common path to dependence in published case series.
Bottom line: Don't use for chronic insomnia. CBT-I, sleep hygiene, and FDA-approved sleep medications are much safer alternatives.
Cognitive enhancement / nootropic claims
Mechanism onlyOnline vendor marketing positions phenibut as a 'nootropic' or 'cognitive enhancer.' There is no controlled human evidence that phenibut improves attention, memory, executive function, or learning in healthy adults. The original Soviet research was clinical (anxiety, sleep, asthenia, pediatric tics, stuttering), not cognitive-performance. Sedative GABA-B agonism is broadly the opposite of cognitive enhancement.
Bottom line: Marketed for cognitive enhancement without evidence and against mechanism. Don't pay for it as a 'nootropic'.
How it works
How to take it
What to track
Bottom line: The honest answer: don't take it. If you are already taking it daily, don't stop abruptly — find a clinician familiar with GHB/benzodiazepine withdrawal and taper under supervision. Withdrawal can include seizures and psychosis.
2 commercial forms
Compare the main delivery options and what they’re best suited for.
Phenibut HCl (hydrochloride)
Most common onlineThe hydrochloride salt is the form sold in most US online and 'smart shop' products. Bitter, acidic taste. Acidic enough to cause oral and esophageal irritation if dosed directly under the tongue or chewed.
Standard oral bioavailability; absorption is rapid and complete.
Phenibut FAA (free amino acid)
Marketed as 'smoother'The neutral free-amino-acid form is marketed as gentler on the stomach and faster-onset. Pharmacologically identical at the receptor level. Marketing differentiation does not reduce dependence or withdrawal risk.
Equivalent pharmacology to HCl form; marketing differentiation is around taste and dosing convenience.
Safety
Know the common side effects, key cautions, and who should avoid it.
Common side effects
Serious risks
Severe physical dependence after weeks of daily use. Tolerance develops within days; physical dependence develops within weeks. Hallmark of GABA-B agonist class.
Life-threatening withdrawal syndrome on abrupt cessation: anxiety, insomnia, tremor, sweating, autonomic instability, psychosis, hallucinations, and seizures. Resembles benzodiazepine and GHB withdrawal. ICU admission and IV benzodiazepine taper required in severe cases.
Acute CNS depression at high doses or combined with alcohol/benzodiazepines/opioids/GHB: coma, respiratory depression, hypothermia. Reversal with benzodiazepines is paradoxical because GABA pathways overlap.
Sold in the US in a regulatory grey zone — the FDA has issued warning letters that phenibut is NOT a lawful dietary ingredient. Online product quality and dosing are unregulated; potency between batches varies widely.
Rising US ED presentations and poison-control calls since online sale began (2009 onward). Documented in multiple US, UK, Australian, and Scandinavian poison-center surveillance studies.
Who should avoid it
- Everyone planning daily, weekly, or other regular self-administered use — dependence and withdrawal risk is real and severe.
- Anyone with a history of substance use disorder, alcohol use disorder, benzodiazepine use, or GHB use.
- People taking alcohol, benzodiazepines, opioids, gabapentinoids, baclofen, GHB, or other CNS depressants — combined use multiplies sedation and respiratory-depression risk.
- Pregnancy and breastfeeding (no human safety data).
- Anyone under 18 — pediatric cases in US ED reports involve severe outcomes including ICU admission.
- People with seizure disorders, severe mental illness (psychosis, bipolar disorder), or severe hepatic/renal impairment.
Pregnancy & breastfeeding
Avoid. There is no human pregnancy safety data. GABA-B agonists cross the placenta and could theoretically cause neonatal sedation and withdrawal. The Soviet prescribing label specifically excludes pregnancy.
Bottom line: Phenibut is a dependence-prone CNS depressant marketed as a supplement in the US contrary to FDA findings. Withdrawal can kill. If you are already using it daily, do not stop abruptly — get supervised taper.
Interactions
Combined CNS depression — additive sedation and respiratory depression. Multiple ED case reports describe coma and respiratory arrest with phenibut + alcohol.
Overlapping GABA pathways multiply sedation. Also: phenibut withdrawal is treated with benzodiazepines — chronic combined use confounds taper and dependence assessment.
Multiplied respiratory depression risk. Phenibut + opioid co-use has been reported in fatal overdose case series.
Similar GABA-class CNS-depressant mechanism. Combined use multiplies sedation and complicates withdrawal management.
Same GABA-B agonist class — cross-tolerance and additive CNS depression. Withdrawal syndromes overlap.
Additive sedation, plus potential interference with the prescribed treatment for the underlying anxiety/depression. Talk to your prescriber.
Additive sedation and orthostatic hypotension; phenibut withdrawal psychosis can be misattributed to underlying psychiatric illness.
Choosing a product
What to look for on the label — and what to be skeptical of.
Look for…
Be skeptical of…
Frequently asked questions
Is phenibut legal?⌄
Phenibut is not approved as a drug in the US, UK, or most EU countries. It is sold as a supplement in some jurisdictions but banned outright in others (Australia, Hungary, Italy, Lithuania). Regulations vary.
Is phenibut addictive?⌄
Yes. Regular use leads to physical dependence, tolerance, and severe withdrawal. Even moderate use over a few weeks can cause significant problems on stopping.
How dangerous is phenibut withdrawal?⌄
Withdrawal can include severe anxiety, insomnia, hallucinations, and seizures. Medical supervision is recommended for anyone with regular use trying to stop.
Can I combine phenibut with alcohol?⌄
No. The combination significantly increases the risk of respiratory depression, blackouts, and death. Many phenibut-related emergencies involve alcohol.
Should I take phenibut for anxiety?⌄
Safer alternatives exist. Even in countries where phenibut is licensed, it is recommended only for short-term, supervised use. Most experts advise against self-medicating with phenibut.
References by claim
Safety
FDA Warning Letter — phenibut is not a lawful dietary ingredient, 2019 — U.S. Food and Drug Administration (2019) link
Owen et al., 2016 — PubMed — Clinical Toxicology (2016) link
Hardman et al., 2019 — PubMed — BMJ Case Reports (2019) link
Joneborg et al., 2022 — PubMed — Frontiers in Psychiatry (2022) link
Cognitive enhancement / nootropic claims
Cohen et al., 2019 — PubMed — Clinical Toxicology (2019) link
Acute anxiolysis (single short-term dose)
Lapin, 2001 — PubMed — CNS Drug Reviews (2001) link
Track Phenibut with Pilora
Set up dose reminders, check interactions, and join the community in the Pilora iPhone app.
Coming to App StoreDisclaimer: This compound is not approved by the FDA for human use and is not a dietary supplement. This page is an educational review of available research — much of it preclinical or early-stage — not a recommendation to use it. Consumer product quality is unregulated. Consult a qualified clinician.