Common questions about Phenibut
What is Phenibut used for?
Phenibut is most often marketed for Marketed for anxiety relief, but there are no rigorous, modern human trials demonstrating safe or effective use as a supplement — anxiolytic and sedative effects are mediated by GABA-B agonism but are unproven for any supplement claim and come with serious dependence risk., Promoted for sleep and as a nootropic/cognitive enhancer; these claims are unsupported by credible controlled human evidence and are outweighed by documented harms., Any short-term subjective calming or euphoric effect rapidly drives tolerance, escalating doses, and dependence rather than durable benefit.. A Soviet-era GABA-B drug sold online as a "calm" supplement — with a brutal dependence and withdrawal profile.
Does Phenibut work — what does the evidence say?
No Evidence evidence. No credible human evidence supports the marketed claims — widely considered ineffective. Phenibut (β-phenyl-GABA) is a central nervous system depressant developed in the Soviet Union that acts mainly as a GABA-B receptor agonist with additional gabapentinoid (α2δ calcium-channel) activity. It is sold online and in "supplement" or nootropic products for anxiety, sleep, and cognitive enhancement, but it is not approved as a dietary supplement or medicine in the US, UK, or Australia, and the FDA has stated it does not meet the definition of a dietary ingredient. There are no rigorous modern human trials supporting safe or effective supplement use, while a substantial case literature documents rapid tolerance, physical dependence, and a severe withdrawal syndrome that can include insomnia, hallucinations, agitation, delirium, and seizures, sometimes within hours of the last dose. Overdose — frequently involving co-ingested alcohol, benzodiazepines, or opioids — can cause profound sedation, reduced consciousness, agitated delirium, and cardiovascular and renal effects, with no specific antidote. Analyses have also found actual phenibut content in marketed products far exceeding label claims, compounding the risk. Given documented harms and absent credible benefit for its marketed claims, the evidence tier for safe supplement use is 'none'.
What is the typical dose of Phenibut?
No safe or approved supplement dose exists. Illicit recreational use is commonly 250–1500 mg, but dependent users escalate dramatically (case-series average ~13.6 g/day); not recommended at any dose.
Is Phenibut safe? Any cautions or side effects?
Not approved as a supplement or medicine in the US, UK, or Australia (banned/prohibited in Australia and restricted in several European countries). Phenibut produces rapid tolerance and physical dependence; abrupt cessation after regular use can cause a severe withdrawal syndrome — anxiety, insomnia, tremor, hallucinations, psychosis, autonomic instability, delirium, and seizures — that may require medically supervised baclofen or benzodiazepine tapering. Overdose causes deep sedation, reduced consciousness, agitation/delirium, low blood pressure, and renal impairment, with no specific antidote; high chronic intake (above ~7 g) has been linked to hepatic effects. Risk is greatly amplified by co-use with alcohol, benzodiazepines, opioids, or other CNS depressants — a common feature of reported toxicity and a potentially fatal combination. Marketed product potency is unreliable and often exceeds label claims, making dosing unpredictable. It must be avoided by anyone who is pregnant or breastfeeding, by people with a history of substance use disorder or psychiatric illness, and by those taking sedatives, GABAergics, or alcohol; do not stop established use abruptly — seek medical supervision.
How many studies support Phenibut?
NutriDex cites 13 sources for Phenibut, graded "No Evidence".
Does Phenibut interact with any medications?
Yes — known or theoretical interactions include: Sedatives (benzodiazepines, opioids, alcohol) (avoid). This is educational and not exhaustive; always check with your doctor or pharmacist before combining Phenibut with any medicine.
Cite this page
APAPeh, D. (2026). Phenibut (β-phenyl-γ-aminobutyric acid): Benefits, Dosage, Side Effects & Evidence. NutriDex — The Supplement Research Compendium. Retrieved 26 Jun 2026, from https://nutridex.info/s/phenibut
BibTeX@misc{nutridex_phenibut,
author = {Peh, Daryl},
title = {Phenibut (β-phenyl-γ-aminobutyric acid): Benefits, Dosage, Side Effects \& Evidence},
year = {2026},
howpublished = {NutriDex --- The Supplement Research Compendium},
url = {https://nutridex.info/s/phenibut},
note = {Reviewed by Dr Daryl Peh, MBBS Singapore, MMed FM. Accessed 2026-06-26}
}
For medical claims, citing the underlying primary studies linked above is preferred. NutriDex is an educational reference, not medical advice.