PhenibutBanned Substance

• The FDA's position here is legal, not toxicological. Phenibut fits none of the Federal Food, Drug, and Cosmetic Act's categories of a lawful dietary ingredient — not a vitamin, mineral, botanical, amino acid, or dietary substance [1].
  
  That alone makes any supplement listing phenibut misbranded under US law, whatever the product's safety record. ^[1]

• In April 2019 the FDA sent warning letters to three companies — Atomixx, Evol Nutrition Associates (dba Red Dawn Energy) and NeuroScience Solutions — over phenibut-containing products sold as supplements [1].
  
  Venable LLP's analysis flags what those letters left out. Unlike most supplement warning letters, they alleged no safety problem at all; the dietary-ingredient definition was the sole basis [2]. ^[2]

• On 2 June 2023 a US District Court entered a permanent injunction against Daniel R. Marold, doing business as "Chill6," over flavored beverage powders containing Phenibut HCl [1].
  
  The FDA describes those products as unapproved and misbranded drugs and adulterated food, labeled with disease claims for insomnia, alcoholism, PTSD and anxiety disorder [1].
  
  The agency separately classifies phenibut as an unsafe food additive. ^[1]

• Enforcement has not actually cleared the market. A 2021 laboratory analysis reported by MedPage Today found phenibut content went up in three of four tested brands after the 2019 warning [3].
  
  Post-warning servings ran from 21 mg to 1,164 mg — as much as 450% more than a standard 250 mg pharmaceutical tablet sold in Russia [3]. ^[3]

• Dependence is the defining hazard. Tolerance builds readily with repeated use, and stopping abruptly can set off a withdrawal syndrome resembling benzodiazepine or baclofen withdrawal [4].
  
  Reported features include rebound anxiety, insomnia, aggression, irritability, agitation, visual and auditory hallucinations, seizures and acute psychosis. Published cases have required ICU admission [4]. ^[4]

• US poison centers logged 1,320 phenibut exposure calls between 2009 and 2019, from all 50 states and DC, in CDC's Morbidity and Mortality Weekly Report [5].
  
  The commonest reported effects were agitation (30.4%), drowsiness or lethargy (29.0%), tachycardia (21.9%) and confusion (21.3%) [5].
  
  Coma occurred in 80 cases (6.2%). Major effects — life-threatening or causing significant disability — were recorded in 12.6% of exposures, and three deaths were reported [5]. ^[5]

• Phenibut is a full agonist at the GABA-B receptor, the same target as baclofen, but with 30- to 68-fold lower affinity — which is why the doses used are so much larger [4].
  
  It also blocks the alpha-2-delta subunit of voltage-gated calcium channels, the mechanism gabapentin and pregabalin use. Pharmacologically it is a gabapentinoid as well as a GABA-B agonist [4]. ^[4]

• Intoxication usually reads as a sedative-hypnotic picture: reduced consciousness, stupor, depressed respiratory drive, bradycardia, bradypnea, hypotension and hypothermia [8].
  
  It can also do the opposite — agitation, hallucinations, seizures, delirium. Severe agitation should raise withdrawal in the differential, not only acute intoxication [8]. ^[8]

• Phenibut's pharmaceutical labeling advises liver and blood monitoring during prolonged, especially high-dose use, citing fatty liver disease and eosinophilia [4].
  
  In overdose, fatty liver degeneration has been associated with amounts above roughly 7 grams [4]. ^[4]

• There is no specific antidote for phenibut overdose or withdrawal. Care is supportive — IV fluids, airway monitoring, benzodiazepines if seizures occur [8]. ^[8]

• The two literatures disagree about how dangerous this is. US poison-center data and US case reports describe coma and respiratory depression, sometimes in the single-digit-gram range [5].
  
  Germany's GIZ-Nord poison center fielded only 17 phenibut inquiries across 2008-2022, against 55 for gabapentin and 126 for pregabalin [6].
  
  In its 15 overdose cases — reported amounts of 2 to 100 g — no patient had respiratory depression or coma, though 8 were somnolent [6].
  
  Co-ingestion of other depressants is common in the more severe US cases, which may account for part of the gap. We are flagging the disagreement, not settling it. ^[6]

• Phenibut came out of Soviet pharmacology in the 1960s and remains an approved medicine in Russia, Ukraine, Belarus, Kazakhstan, Georgia and Latvia [4].
  
  It has never been approved as a medicine in the US, most of the EU, or Australia. In those markets it circulates online, marketed as a supplement or nootropic [4]. ^[4]

• Australia moved first and hardest. Its Therapeutic Goods Administration ran a formal scheduling review in 2017, citing case reports of significant toxicity, dependence and withdrawal risk, including Australian ones [12].
  
  The delegate's final decision created a new Schedule 9 (Prohibited Substance) entry effective 1 February 2018 — the strictest Australian poisons category [12].
  
  The stated reasons were tolerance, dependence, abuse and overdose requiring hospitalisation up to ICU care, against no established therapeutic benefit and no ARTG-listed product [12]. ^[12]

• Germany controls phenibut as a food supplement under its New Psychoactive Substances Act (Neue-psychoaktive-Stoffe-Gesetz), banning production, possession, use, trafficking and administration [6].
  
  The same 2024 paper notes it nonetheless remains easy to order online there [6]. ^[6]

• The UK does not schedule phenibut under the Misuse of Drugs Act 1971. It is caught instead by the blanket Psychoactive Substances Act 2016 [13].
  
  Production, supply, offering to supply and importation are all offences. Simple possession for personal use is not, except inside a custodial institution [13]. ^[13]

• France added phenibut to its list of controlled psychoactive substances on 18 September 2020, prohibiting production, sale, storage and use outright [4].
  
  Hungary added it to its New Psychoactive Substances ban list on 14 November 2018, and Italy did the same on 26 August 2020 [4]. ^[4]

• US federal action has been narrower and slower — warning letters in April 2019 and misbranding litigation ending in the June 2023 injunction, rather than a categorical ban [1].
  
  Phenibut itself stays legal to possess and buy federally, so long as it is not marketed as a dietary supplement [5].
  
  Alabama is the exception. The state classified phenibut as a Schedule II controlled substance in November 2021 [4]. ^[1]

• Canada has not specifically scheduled phenibut under its Controlled Drugs and Substances Act, and Health Canada has not approved it as a therapeutic or dietary product [18].
  
  Its status there is genuinely ambiguous rather than settled in either direction [18]. ^[18]

No validated human toxic threshold exists for phenibut. Controlled dosing studies are essentially absent, so every figure below comes from case reports, poison-center records or pharmaceutical labeling [15].

Where it is an approved drug, it is sold as 250 mg or 500 mg tablets, or a 10 mg/mL infusion solution [4]. A single 250 mg oral dose had a half-life of about 5.3 hours in healthy volunteers, with roughly 63% excreted unchanged [4].

A systematic review described 250-2,000 mg/day as the therapeutic range generally tolerated with few side effects [10].

Published acute-toxicity case reports describe single oral doses from about 1 gram to 30 grams [15]. Germany's GIZ-Nord recorded reported overdose amounts of 2 to 100 grams [6].

Measured concentrations: 29.7 and 36.5 microg/mL in plasma in two emergency-department cases with altered mental status [17]. In one fatality report, postmortem blood was 64.0 mg/L in one decedent and under 1.0 mg/L in the other [7].

Labeling is unreliable, so a "serving" is not a known amount — tested over-the-counter products ranged from 21 mg to 1,164 mg per serving [3].

Sources disagree sharply on what counts as a dangerous single amount. Clinical/pharmaceutical reports and recreational/poison-center reports are using different yardsticks entirely [15]. ^[15]

Unintentional exposure is largely a pediatric pattern. In US poison-center data, 93.3% of exposures among children under 10 were unintentional, against 6.3% of adult exposures [5].

Across all cases under 18, 21.9% were unintentional. Co-ingestion of another substance was reported in 29.6% of under-18 cases and 40.2% of adult cases [5].

Most exposures involved solids such as tablets (65.1%) or powder (24.8%). Ingestion accounted for 93.2%, with 2.8% by inhalation and 4.0% by other routes including dermal [5].

Routine drug screens do not detect it. No commercially available immunoassay picks up phenibut, so it does not appear on standard urine panels [5].

Confirmation needs GC-MS or LC-MS/MS testing that most hospital labs do not run. Emergency diagnosis is therefore usually clinical, from history and presentation [16].

One quirk from the literature: phenibut's benzene ring can interfere with methamphetamine immunoassays, sometimes returning an unreportable result that hints at the diagnosis [16].

There is no specific antidote. For severe cases — impaired consciousness, respiratory depression, arrhythmia signs, or suspected multidrug intoxication — intensive monitoring with ventilation on standby for about 12 hours is advised [6].

In the US, a suspected exposure goes to Poison Control on 1-800-222-1222, or to emergency care [5]. ^[5]