Last reviewed September 2026
Phenibut carries real risks. Older articles online, including earlier versions of this site, played them down. Here’s what the medical and public health record shows.
Tolerance and dependence
The body adapts to phenibut quickly. A 2021 review for the World Health Organization found that tolerance can develop within one to two weeks of regular use. People then take more to get the same effect, and at that point stopping can bring on withdrawal. Case reports describe people who kept raising the amount and couldn’t stop even after it was clearly causing them problems.
Withdrawal can be serious
Withdrawal from regular phenibut use can include severe anxiety, insomnia, agitation, hallucinations and, in some cases, seizures and delirium. Some people have needed hospital care. Our withdrawal page covers this in detail. If you’ve been using phenibut daily, talk to a doctor before stopping.
Poisonings and overdoses
The CDC looked at phenibut cases reported to U.S. poison centers from 2009 through 2019. There were 1,320 in all, with a sharp rise after 2015. Most involved adults aged 18 to 34.
- About half had moderate effects that didn’t cause lasting harm.
- About 1 in 8 had major, life-threatening effects.
- 80 people went into a coma.
- 3 people died.
The most common problems were agitation, drowsiness, a fast heartbeat and confusion.
Mixing with other drugs
About 40 percent of the adult poison center cases involved other substances too. Phenibut adds to the sedating effect of alcohol, opioids, benzodiazepines, gabapentin, pregabalin and sleep medicines. With opioids in particular, doctors warn about slowed breathing and a higher risk of fatal overdose.
You can’t be sure what’s in the product
Because phenibut isn’t an approved drug in the U.S., nobody checks the dose or purity of what’s sold. A 2021 study found some phenibut products held several times more of the drug per serving than a standard pharmaceutical tablet, and some supplements kept advertising phenibut after the FDA’s warnings.
Limited research
Most of what’s known about phenibut as a medicine comes from Russia and the former Soviet Union. It hasn’t gone through the kind of large trials that U.S. or European regulators require, and long-term effects aren’t well studied.
When to get help right away
Call 911 if someone who has taken phenibut:
- is very drowsy or hard to wake
- is breathing slowly or shallowly
- is confused or seeing things that aren’t there
- has a seizure
For questions about an exposure that isn’t an emergency, call Poison Help at 1-800-222-1222. More options are on our getting help page.
Sources
- CDC, Notes from the Field: Phenibut Exposures Reported to Poison Centers — United States, 2009–2019, MMWR, 2020
- World Health Organization, Pre-Review Report: Phenibut, 2021
- Bonnet U. et al., Phenibut: an illegal food supplement with psychotropic effects and health risks, Deutsches Ärzteblatt International, 2024
- Center for Science in the Public Interest, FDA urged to crack down on marketers of illegal drug phenibut, 2021
- FDA, Phenibut in Dietary Supplements