Phenibut

Is phenibut safe?

No. Phenibut was developed in the Soviet Union in the 1960s and is still a prescription medicine in Russia for anxiety and sleep, but in the US it has never been approved and the FDA says it cannot be sold as a dietary supplement. It acts on GABA-B receptors, the same system as alcohol and the muscle relaxant baclofen, and it sedates. Tolerance builds quickly, and withdrawal after daily use can be severe.

It scores 25, close to kratom at 29 and a little above tianeptine at 19. All three are sold as nootropics or supplements, cause dependence and lack a lawful route to sale in the US. Phenibut scores slightly above tianeptine because it has not drawn a federal scheduling proposal or a Class I recall.

Is phenibut legal?

In April 2019 the FDA sent warning letters to three companies selling phenibut supplements, some marketed as sleep aids. Its constituent update said: "Phenibut does not meet the definition of a dietary ingredient under the Federal Food, Drug, and Cosmetic Act (FD&C Act). Products labeled as dietary supplements that list phenibut as a dietary ingredient are misbranded."

That stops short of a ban. Phenibut is not a controlled substanceControlled substanceA medicine or drug that the law restricts because it can be misused or cause dependence. Countries group them into schedules or classes.More in the glossary in the US, so possessing it is not a crime, and sellers switched to labels such as "research chemical" or "not for human consumption". A 2022 study found that FDA warnings had little effect on what was in the bottle (see below).

Elsewhere the rules are tighter. In 2017 the advisory committees to Australia's Therapeutic Goods Administration recommended adding phenibut to Schedule 9 of the Poisons Standard, the list of prohibited substances, citing case reports of serious toxicity and dependence. A 2024 review lists France, Italy and Lithuania among the European countries that prohibit it.

What happens in an overdose?

US poison centres recorded 1,320 phenibut exposures from 2009 to 2019, according to CDC, with cases rising sharply after 2015. Most came from hospitals and involved men aged 18 to 34.

Effect or outcome	Share of cases
Agitation	30.4%
Drowsiness or lethargy	29.0%
Fast heart rate	21.9%
Confusion	21.3%
Coma	6.2% (80 cases)
Major (life-threatening) effects	12.6%

Three people died, one with no other substance involved. Phenibut can cause both sedation and agitation, sometimes in the same person, which makes it hard to recognise in an emergency room. Routine drug screens do not test for it.

Young people are at particular risk. A 2024 review describes five 15-year-olds in Australia who needed a breathing tube after taking an estimated 1,250 to 1,750 mg each over three hours. They kept taking capsules because they thought the first ones had not worked.

Why withdrawal is the bigger problem

Most people who get into trouble with phenibut do so after weeks or months of daily use. Users report taking around 2,400 mg a day on average in one survey cited by the 2024 review, nearly ten times a Russian tablet, and some reach 9,000 mg or more. When they stop, rebound anxiety, insomnia, tremor and agitation follow. In severe cases there are hallucinations, delirium and psychosis needing hospital treatment. The review calls withdrawal "the most frequent and nearly unavoidable consequence of long-term ingestion".

This resembles withdrawal from alcohol or benzodiazepines, and it is managed the same way: a gradual, supervised taper, sometimes with baclofen. If you take phenibut daily, talk to your doctor before you stop. Do not try to quit abruptly on your own.

What is in the bottle?

Little matches the label. A 2022 study bought four phenibut supplements before and after the FDA warnings. After the warnings all four contained phenibut, at 21 mg to 1,164 mg a serving, and three had more than before. The highest dose was about 4.5 times a 250 mg Russian tablet. A 2024 study of six products bought online found three with much less phenibut than declared, one with considerably more, and undeclared ingredients in every capsule.

Who should avoid it

Everyone, by the standard we apply to supplements, and in particular:

• Anyone who drinks alcohol or takes benzodiazepines, opioids, sleeping pills, antipsychotics, anticonvulsants or gabapentinoids such as gabapentin and pregabalin. The sedation adds up.
• Young adults, who made up 58.4% of US poison centre cases (aged 18 to 34), and teenagers.
• People with anxiety or insomnia looking for a non-prescription fix. Rebound anxiety and insomnia are typical withdrawal symptoms, so the original problem can come back harder.
• Pregnant or breastfeeding women.

If someone who has taken phenibut is very hard to wake, breathing slowly, confused or severely agitated, call 911. For advice on a suspected poisoning, call Poison Help at 1-800-222-1222 (US).

How we scored it

Regulatory actions (15), dose safety (20) and product quality (20) are the weakest factors: the FDA rejects phenibut as a dietary ingredient, dependence and withdrawal are common at the doses people take, and labels are unreliable. Interactions (30) reflect stacked sedation with alcohol and many medicines. Organ toxicity (40) is higher because harm falls on the brain rather than the liver, kidneys or heart.