Substance guides

Phenibut addiction: The legal supplement with dangerous withdrawal

Published August 18, 2025 · 7 min read · Updated April 2026

Reviewed for accuracy by licensed clinical professionals.

Phenibut is a GABA-B agonist sold as a supplement in the US despite being a prescription medication in Russia. It produces anti-anxiety and euphoric effects similar to alcohol and benzodiazepines.

How it works

Phenibut crosses the blood-brain barrier and acts on GABA-B receptors (similar to baclofen) and voltage-gated calcium channels (similar to gabapentin). At recreational doses, it produces relaxation, euphoria, reduced social anxiety, and disinhibition.

Dependence develops rapidly

Tolerance can develop within days of daily use. Physical dependence occurs within 1-2 weeks of regular use. Withdrawal symptoms are severe and potentially dangerous.

Withdrawal

Anxiety (often more severe than baseline), insomnia, tremors, psychosis, hallucinations, and in rare cases seizures. Phenibut withdrawal resembles benzodiazepine withdrawal and requires medical management. Baclofen tapering is the most studied approach.

The legal gap

Phenibut is sold freely online and in supplement stores despite producing effects and dependence comparable to controlled substances. The FDA has warned manufacturers but has not scheduled the substance.

Authoritative sources

This article references guidelines from: SAMHSA · NIDA · ASAM

Frequently asked questions

Is phenibut addictive?

Yes, highly. Physical dependence develops within 1-2 weeks of daily use. Withdrawal can be severe and dangerous.

Is phenibut withdrawal dangerous?

Yes. Withdrawal can include seizures, psychosis, and severe anxiety. Medical management is recommended.

Is phenibut legal?

Currently legal to purchase as a supplement in the US, though the FDA has issued warnings. It is a prescription medication in Russia.

Disclaimer: Informational only. Not medical advice. SAMHSA: 1-800-662-4357.