Short answer: Phenibut is a sedative related to GABA and baclofen, prescribed for anxiety and sleep in Russia and Latvia. In the US it is not approved and cannot legally be sold as a dietary supplement, but it is sold online. Daily use can cause severe withdrawal with agitation, hallucinations, and seizures.
Key takeaways
- What it is: Phenibut is a gaba-b receptor agonist (unapproved supplement) and not a federally controlled substance.
- Medical use: None in the US (prescribed in Russia and Latvia).
- Timing: effects start in 2 to 4 hours and last 15 to 24 hours.
- Most dangerous mix: Alcohol, which can cause deep sedation, vomiting, stopped breathing.
- Naloxone: it does not reverse this drug, but give it whenever opioids could be involved.
- Dependence risk: High.
- Legal route: phenibut is not federally scheduled as of October 2026, but state bans, FDA restrictions, and pending federal action can apply; check current status.
What is phenibut?
Phenibut was developed in the Soviet Union in the 1960s and is prescribed there for anxiety, insomnia, and other conditions.
Phenibut causes relaxation, reduced anxiety, sociability, and sleepiness. Because it takes hours to work, people often take extra doses before the first takes effect.
Quick facts
| Fact | Phenibut |
|---|---|
| Chemical name | Beta-phenyl-gamma-aminobutyric acid |
| Drug class | GABA-B receptor agonist (like baclofen); gabapentinoid activity |
| US legal status | Not controlled; not FDA-approved; illegal as a dietary supplement |
| Approved elsewhere | Russia, Latvia (anxiety, insomnia) |
| Forms | Powder, capsules |
| Onset | 2 to 4 hours (slow) |
| Duration | 15 to 24 hours |
How long does phenibut last?
- Starts working: 2 to 4 hours
- Effects last: 15 to 24 hours
It is slow, often 2 to 4 hours, which leads people to take extra doses.
Timing varies with the dose, the form, how it is taken, liver and kidney function, age, and other drugs taken at the same time.
What are the biggest risks of phenibut?
Overdose: deep sedation, confusion, and unconsciousness, especially with alcohol or other sedatives.
Dependence: tolerance develops within days to weeks of daily use.
Severe withdrawal: see below; it can resemble alcohol or benzodiazepine withdrawal.
What should you never mix with phenibut?
| Combined with | What happens | Guidance |
|---|---|---|
| Alcohol | Deep sedation, vomiting, stopped breathing | Dangerous |
| Benzodiazepines, gabapentinoids, opioids | Profound sedation | Dangerous |
| Baclofen | Additive GABA-B effects | Avoid |
Check any combination with the DoseUses combination checker or ask a pharmacist.
What are the signs of a phenibut overdose, and what should you do?
Overdose causes extreme sleepiness, confusion, agitation alternating with stupor, low muscle tone, and coma.
If someone may have overdosed
- Call 911 if the person is unresponsive, hard to wake, or breathing slowly.
- For advice when the person is awake and stable, call Poison Help at 1-800-222-1222 (US, free, 24 hours).
- If opioids could be involved, including pills not from a pharmacy, give naloxone if you have it. Naloxone does not reverse phenibut, but it will not harm the person.
- Stay with the person and place them on their side if they are drowsy or vomiting.
What is phenibut withdrawal like, and how long does it last?
People who take phenibut daily can develop strong physical dependence. Withdrawal can be severe and may need hospital care.
- Hours to day 1Symptoms beginRebound anxiety, insomnia, tremor, and irritability.
- Days 1 to 5PeakAgitation, hallucinations, psychosis, and, in severe cases, seizures.
- 1 to 2 weeksResolvesSymptoms ease; anxiety and sleep problems can linger.
See the withdrawal timelines and the full phenibut withdrawal guide.
Is phenibut legal?
Phenibut is not a federally controlled substance. It is not an approved drug, and the FDA has said it cannot be sold as a dietary supplement.
- State law: Alabama and some other states have banned it.
Outside the United States
| Country | Status |
|---|---|
| Australia | Schedule 9 prohibited substance (since 2018) |
| Russia and Latvia | Prescription medicine |
| International | Not under UN control |
Frequently asked questions about phenibut
Is phenibut legal?
It is not federally controlled, but it cannot legally be sold as a supplement, and some states ban it.
Is phenibut addictive?
Yes. Daily use can cause dependence and severe withdrawal.
How long does phenibut take to work?
It is slow, often 2 to 4 hours, which leads people to take extra doses.
Is phenibut like gabapentin?
It has some similar activity, but it mainly acts on GABA-B receptors like baclofen.
Can phenibut withdrawal cause seizures?
Yes, in severe cases.
Sources
- Notes from the Field: Phenibut Exposures Reported to Poison Centers, United States, 2009 to 2019, Centers for Disease Control and Prevention, MMWR, 2020.
- National Helpline, Substance Abuse and Mental Health Services Administration.
- FindTreatment.gov, Substance Abuse and Mental Health Services Administration.
- International drug control conventions, United Nations Office on Drugs and Crime.
This guide summarizes the sourced DoseUses Phenibut profile, written from FDA labels, DEA rules, and federal health agencies. It is educational and is not medical advice. Last updated October 5, 2026.
