Delynn Willis had suffered from anxiety for years, but she’d always been wary of treating it with drugs like Valium and Xanax. “I didn’t want to start using anything that might lead to an addiction,” says Willis, a writer.

While traveling through Southeast Asia, she stumbled on an alternative option: a drug called phenibut (pronounced fen-uh-byoot), available over the counter as an anti-anxiety aid. A friend told her it was safer than benzodiazepines like Xanax, so she decided to give it a try.

Developed by Russian scientists more than a half-century ago, phenibut has recently exploded in popularity worldwide. In most countries, including the United States, it’s easily available online without a prescription. Some users report that it quells their anxious symptoms, and some say it fosters clear thinking or even ecstasy-like effects. But experts warn that the drug’s addictive potential resembles that of benzos — and that phenibut purchased online may not be safe, since the online phenibut market is largely unregulated.

A “New Tranquilizer”

When Soviet Union researchers first synthesized phenibut in the 1960s, they noticed that it had strong sedative effects on cats and mice. They billed the drug as a “new tranquilizer” that relieved anxiety, improved sleep quality and lifted depression. Phenibut quickly came into widespread use and was even included in cosmonauts’ space kits to help them keep a cool head under pressure.

Chemically, phenibut is similar to the neurotransmitter GABA (gamma-aminobutyric acid), which reduces the excitability of brain cells. That helps explain why people report feeling relaxed and happy when they take it. “It helped me deal with social anxiety without clouding my mind,” Willis says. In that sense, says University of Michigan psychiatrist Edward Jouney, phenibut is actually a close cousin to drugs in the benzodiazepine family, which also affect the brain’s GABA receptors.

Phenibut’s short-term effects are highly dependent on what dose you take. If you take a small amount, under 1 gram, you’re likely to feel a sense of calm and well-being. But at higher doses, your thinking typically blurs, your motor coordination gets loopy and you may lapse into a deep sleep.

Flirting With Dependence

Phenibut’s similarity to benzos means that — despite the popular perception that the drug is safe — your brain can start to grow dependent on it over time, just as it would on Valium or Xanax. “The drug has very potent psychoactive properties,” Jouney says. “There’s evidence it can cause addiction.”

Jouney began researching phenibut’s effects a few years ago, when patients at his clinic told him they’d started the drug and were finding it impossible to stop. The deeper he dug, the more uneasy he became.

Not only were users reporting growing dependence on phenibut, but cases of phenibut-related dissociation, psychosis, and respiratory depression were also cropping up around the country. The CDC reports that poison center calls related to phenibut have been growing since 2015, with users experiencing symptoms like agitation, irregular heartbeat, confusion and even coma.

A Pharmaceutical Wild West

Jouney thinks it’s possible that, used under a doctor’s supervision, phenibut could one day prove a viable treatment for anxiety. The trouble is that clear evidence of the drug’s safety and effectiveness is lacking — and to add to the potential danger, many people are purchasing phenibut from unregulated online sellers.

Phenibut is technically legal to possess in the United States, but that doesn’t mean it’s risk-free — or that you get what you pay for when you order it. Jouney contacted several online phenibut suppliers to ask about their products and quality-control measures, but was rebuffed: “I tried calling them and they wouldn’t give me any info.” In 2019, the FDA sent warning letters to three companies for branding their phenibut products as “dietary supplements,” but most online phenibut sellers continue to ply their wares unchecked.

While Delynn Willis’s phenibut journey started off smoothly, she soon experienced the backlash many users describe. “After I had been using it for a few weeks, I started to notice I needed higher and higher doses to get the same effect,” she says. She started weaning herself off of the drug and got hit with a torrent of withdrawal symptoms. “My anxiety skyrocketed, my temper shortened and I experienced dizzy spells.”

That kind of torturous backlash is why Jouney urges people to reject claims that phenibut is a safe Xanax alternative. “It’s something that should be regulated,” he says. “It can lead to physical dependence. This is not a benign substance.”