This page shows what was measured, who it was measured in, and what that does not settle.
What Phenibut does in the body
An anxiety and sleep drug on prescription in Russia and Latvia. In the United States it is a supplement-aisle product that produces coma in about one in sixteen reported exposures
Phenibut is GABA with a phenyl ring bolted on, which lets it cross into the brain — plain GABA cannot. Once there it activates the GABA-B receptor, the same one baclofen uses, producing calm and sedation. It also binds the calcium-channel subunit that gabapentin targets, and in fact binds that four times more tightly than it binds GABA-B. Effects come on slowly, over hours, which is why people take a second dose before the first has peaked. Stopping after regular use produces a rebound withdrawal that can include agitation, hallucinations and seizures.
What happened in people
1,320 phenibut exposures reported from all 50 states and DC over 2009-2019, with coma in 6.2%, major effects in 12.6% and three deaths
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
The recorded finding that sits closest to something a person would notice. Written into the record, not signed off, and it carries no population or interval.
No recorded sentence describes the change this makes in a way that stands on its own. The page opens with what it is taken for instead, and the recorded explanation follows below.
Shown as the opening line on this page.
A limit recorded against this substance. Not signed off as a reviewed claim.
The four opening statements run to 149 words.
Words this page uses
Four words worth knowing first
Chosen from what this page shows, with each one explained before the word it depends on.
Biomarker
A biomarker is a number from a test that stands in for something about health.
A picture of it, and where the picture fails
A biomarker is like a fuel gauge.
Where that stops being true. A gauge is wired to the tank. Many biomarkers are only loosely tied to health.
What people get wrong. A better number is read as a better life. Several medicines improved a number and helped nobody.
A measurable indicator used as a substitute for a clinical outcome of interest.
Placebo
A placebo is a dummy treatment given so the real one can be compared with it.
A picture of it, and where the picture fails
A placebo is like a blank control in an experiment.
Where that stops being true. A blank does nothing. People given a placebo often do get better.
What people get wrong. A placebo effect is read as imaginary. The improvement is measured and real.
An inactive intervention matched in appearance to the test intervention, used to control for non-specific effects.
Comparator
A comparator is whatever the treatment was measured against.
A picture of it, and where the picture fails
It is like the other runner in a race.
Where that stops being true. A race has one winner. A study can show both arms improved.
What people get wrong. Results are read without asking what the other group got. Beating nothing is not beating a treatment.
The control condition against which the experimental intervention is assessed.
What happened in people◇Read from sources, not yet reviewed
What happened in people
Each card is one study: the exact question it asked, who was in it, and whether it showed what it set out to show.
Number, characteristics and outcome severity of phenibut exposures
✓ The study showed what it set out to show
Who was studied
Graves et al. 2020 National Poison Data System analysis, 2009-2019
How many people
1320
Study design
National surveillance analysis
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
Coma in 80 (6.2%); moderate effects 49.6%; major effects 12.6%; three deaths. Among single-agent exposures, 10.2% major effects including one death
Repeated elsewhere
Replicated
What this does not prove. Meeting one endpoint in one population does not carry to other goals or other people.
The limits of this study, and where it came from
Main limit. Case ascertainment changed in 2015 when poison centres gained a "phenibut" coding term, so the apparent trend confounds a real increase with improved detection. Poison-centre data count calls, not exposures.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral tablet, capsule or bulk powder
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
Phenibut content per serving in supplements on sale before and after FDA warnings
✓ The study showed what it set out to show
Who was studied
Cohen et al. 2022 supplement content analysis before and after FDA warnings
How many people
4
Study design
Analytical product survey
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
Before: 2 of 4 contained phenibut at 484 mg and 487 mg per serving. After: 4 of 4 contained it, 21 mg to 1,164 mg per serving, up to 450% of a 250 mg Russian pharmaceutical tablet
Repeated elsewhere
Unreplicated
What this does not prove. Meeting one endpoint in one population does not carry to other goals or other people.
The limits of this study, and where it came from
Main limit. Four brands is a small sample, chosen because they were available both before and after the warning. The finding is a direction of change in a selected set, not a market-wide estimate.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral tablet, capsule or bulk powder
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
Incidence, reasons for use and clinical effects of phenibut exposure calls
✓ The study showed what it set out to show
Who was studied
McCabe et al. 2019 Minnesota Poison Control System review, 2000-2018
How many people
56
Study design
Regional poison-centre case series
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
48 of 56 calls (85.7%) in the final five years; CNS effects in over 50%; 11 of 56 (19.6%) intubated; no deaths
Repeated elsewhere
Replicated
What this does not prove. Meeting one endpoint in one population does not carry to other goals or other people.
The limits of this study, and where it came from
Main limit. Single-state data with 56 cases over nineteen years. Co-ingestants documented in 35.7%, so not all clinical effects are attributable to phenibut alone.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral tablet, capsule or bulk powder
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
RNAWiki holds 3 written-up human studies for this substance, each with the question it asked.
How we know it
Each card names the study, the number of people and what the study set out to measure.
What this does not prove
These summaries were written by a person and have not been signed off as reviewed claims.
Why it matters
A study that failed is as informative as one that worked, and both are here.
What we still do not know
No reviewed claim exists, so no exact population, effect size or interval is published yet.
What it changes in the body◇Read from sources, not yet reviewed
The path through the body
From what a person takes to what changes. A solid line is a step measured in people. A dashed line is a step nobody has measured that way.
Start
Phenibut
What a person takes: Oral tablet, capsule or bulk powder.
The measurement behind this step
The licensed pharmaceutical abroad is a 250 mg tablet. The US market is capsules, tablets and bulk powder sold by weight, and bulk powder is the formulation most implicated in large doses — a user measuring a gram-scale amount by eye is working with a molecule whose effect takes hours to appear.
Getting in
Swallowed as powder or tablet
A Russian pharmaceutical tablet is 250 mg. US supplement servings analysed after the FDA warning ranged from 21 mg to 1,164 mg.
╌╌Described, with no measurement named. No measurement is named for this step, so it is drawn as an unconfirmed link.
The measurement behind this step
Oral phenibut hydrochloride, most often as a solid (65.1% of exposures with known formulation) or bulk powder (24.8%). Bulk powder weighed by the user is the formulation most associated with large accidental doses.
GABA itself cannot cross into the brain from the blood. Adding a benzene ring makes the molecule lipophilic enough to get in.
╌╌Described, with no measurement named. No measurement is named for this step, so it is drawn as an unconfirmed link.
The measurement behind this step
The β-phenyl substitution is the entire design rationale: it confers the lipophilicity that permits blood-brain barrier penetration, which unmodified GABA lacks. Onset is slow, over hours, and elimination is predominantly renal.
It hits two unrelated targets: the one gabapentin uses and the one baclofen uses. In the active enantiomer the gabapentin target is the tighter fit.
╌╌Described, with no measurement named. No measurement is named for this step, so it is drawn as an unconfirmed link.
The measurement behind this step
R-phenibut Ki 23 µM at the α2-δ subunit versus 39 µM for S-phenibut, 156 µM for baclofen and 0.05 µM for gabapentin; R-phenibut binds α2-δ about four times more tightly than GABA-B. S-phenibut does not bind GABA-B at all. The antinociceptive effect survives GABA-B antagonism, attributing it to α2-δ.
The intended effect is calm. Above that, agitation and confusion are as common as drowsiness, and coma occurred in about one in sixteen reported exposures.
╌╌Described, with no measurement named. No measurement is named for this step, so it is drawn as an unconfirmed link.
The measurement behind this step
Reported effects across 1,320 exposures: agitation 30.4%, drowsiness or lethargy 29.0%, tachycardia 21.9%, confusion 21.3%, coma 6.2%. Major effects in 12.6% overall and 10.2% of single-agent exposures. Respiratory depression is the reason 19.6% of a regional series required intubation.
After regular use, stopping produces agitation, hallucinations and in some reports seizures — a picture closer to alcohol or benzodiazepine withdrawal than to opioid withdrawal.
╌╌Described, with no measurement named. No measurement is named for this step, so it is drawn as an unconfirmed link.
The measurement behind this step
GABA-B system rebound following chronic agonism, the same mechanism as baclofen withdrawal. Withdrawal concerns were recorded in 10.7% of the Minnesota series. The structural identity with baclofen is why baclofen itself appears as a management strategy in reported cases.
No suggested links are held for this record, so nothing is hidden from this path.
What we know
The record describes 5 steps from taking it to an effect in a person.
How we know it
Each step names the study behind it in the technical detail beside it.
What this does not prove
A change inside the body is a reason to look. It is not a result in a person.
Why it matters
A reader can see exactly where the chain stops being measured in people.
What we still do not know
No reviewed claim binds any of these steps to a named population.
What is missing or unclear◇Read from sources, not yet reviewed
Were people like you studied?
RNAWiki cannot tell whether a study fits you. It can show who was in it, and where the result stops carrying.
Who was studied
People similar to this profile were included.
In the 2009-2019 US poison-centre data: 75.5% male, 58.4% aged 18 to 34, mean age 31.7. Where it is licensed, patients on prescription.
Who is missing from the studies
Which groups were under-represented in the studies has not been recorded for this substance. Pregnancy, breastfeeding, children, older adults, and people with liver or kidney conditions are commonly excluded from trials; nothing here says whether they were.
Where the result stopped carrying
FDA advisories that phenibut is not a permitted dietary ingredient were followed by higher measured content in three of four tested brands
No randomised controlled trial in the peer-reviewed English-language literature supports any indication; the licensed uses abroad rest on an older Soviet-era evidence base
This is a scope explorer, not a diagnosis engine.
It shows who was studied so you can see whether people similar to you were included.
RNAWiki cannot tell whether a study fits you. It can show who was in it.
What it would be like to take◇Read from sources, not yet reviewed
Why it might seem to do nothing
A real effect and a noticed effect are different things. These are the recorded reasons the two come apart.
It was studied in different people
The people in the studies were not much like the reader.
On this record: Which groups were under-represented in the studies has not been recorded for this substance. Pregnancy, breastfeeding, children, older adults, and people with liver or kidney conditions are commonly excluded from trials; nothing here says whether they were.
The evidence may simply be wrong
Small early studies often do not hold up.
On this record: RNAWiki has not yet published a reviewed conclusion for this use.
Other reasons RNAWiki checked and found nothing for (11)
It was studied for a different goal
The studies measured something else entirely. Nothing in this record points to this reason.
A different form was studied
The studied form is not the form on the shelf. Nothing in this record points to this reason.
There was nothing to correct
Where a level is already normal, topping it up may change nothing. Nothing in this record points to this reason.
Something else had to happen too
In the studies it was paired with training, a diet or another treatment. Nothing in this record points to this reason.
The change is too small to feel
A real change can still sit below what a person notices. Nothing in this record points to this reason.
Day-to-day swing hides it
Sleep, food, stress and time of day move most numbers more than this would. Nothing in this record points to this reason.
Not enough time yet
The studies ran longer than the person has waited. Nothing in this record points to this reason.
It was not taken as studied
Missed days change the result, and studies count them. Nothing in this record points to this reason.
Something else changed at the same time
Two changes at once cannot be told apart afterwards. Nothing in this record points to this reason.
The product may not be what it says
Contents of a sold product are not always what the label states. Nothing in this record points to this reason.
No recorded reason
RNAWiki has nothing stored that would explain it. Nothing in this record points to this reason.
None of these is a reason to take more. Taking more is not a step this page ever suggests.
What it would be like to take◇Read from sources, not yet reviewed
What taking it involves
The recorded facts about getting hold of it and using it. Nothing here is a suggestion about what you should do.
How it is supplied
Varies by country
❝ Quoted from a source
Where this came from
Copied from a source RNAWiki stored, with the source named.
Read from the recorded approval status.
No source is stored against this line.
Form and route
Oral tablet, capsule or bulk powder
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
The form and route recorded on this substance.
No source is stored against this line.
Who oversees it
Not usually supervised: sold as a supplement or food ingredient where recorded. That is a legal category, not a safety judgement.
❝ Quoted from a source
Where this came from
Copied from a source RNAWiki stored, with the source named.
The identity record classes it as a supplement ingredient; no medicines register records an approval.
No source is stored against this line.
What is in the pack
The licensed pharmaceutical abroad is a 250 mg tablet.
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
Recorded notes on how this is sold. The rest of the recorded wording: The US market is capsules, tablets and bulk powder sold by weight, and bulk powder is the formulation most implicated in large doses — a user measuring a gram-scale amount by eye is working with a molecule whose effect takes hours to appear.
No source is stored against this line.
Where it is registered
Not recorded.
∅ Nothing recorded
Where this came from
RNAWiki holds nothing here and says so rather than guessing.
No register entry is recorded.
No source is stored against this line.
Why people stop
Not recorded.
∅ Nothing recorded
Where this came from
RNAWiki holds nothing here and says so rather than guessing.
No record of why people stopped taking it is stored for this substance.
No source is stored against this line.
What it would be like to take◇Read from sources, not yet reviewed
What can go wrong
Sorted by where each line came from. A regulator's label and a report somebody sent in are not the same kind of fact.
·Worth asking a clinician aboutWritten into the record from the studies named on this page
Slow onset over several hours invites redosing before the first dose has peaked. Reported acute effects across 1,320 exposures were agitation 30.4%, drowsiness 29.0%, tachycardia 21.9%, confusion 21.3% and coma 6.2%, with major effects in 12.6% and three deaths; a regional series intubated 19.6% of patients. Combination with alcohol, benzodiazepines or opioids compounds the respiratory depression, and co-exposure was documented in about 40% of adult cases. Chronic use produces dependence with a rebound withdrawal syndrome that can include agitation, hallucinations and seizures, managed in reported cases with benzodiazepines or baclofen. Phenibut is renally cleared and is not detected by routine toxicology screening. It is also the commonest co-exposure recorded in US tianeptine poison-centre calls.
Nobody counted how many people took this and were fine, so this cannot be turned into a rate.
Over a long time. No completed tested study window is recorded, so long-term effects are not established by the registry record.
Groups the studies covered thinly. Which groups were under-represented in the studies has not been recorded for this substance. Pregnancy, breastfeeding, children, older adults, and people with liver or kidney conditions are commonly excluded from trials; nothing here says whether they were.
What is missing or unclear◇Read from sources, not yet reviewed
Does the exact form matter?
Evidence belongs to the exact thing that was tested. A different salt, a different mixture or a different preparation is a different question.
The form that was studied
Oral tablet, capsule or bulk powder
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
The form used in the studies cited on this page.
No source is stored against this line.
What is sold
A recorded note compares this form with the others that are sold. It is kept below, word for word.
§ A fixed RNAWiki sentence
Where this came from
Wording RNAWiki always uses, not a finding about this substance.
The recorded note, unchanged: The US market is capsules, tablets and bulk powder sold by weight, and bulk powder is the formulation most implicated in large doses — a user measuring a gram-scale amount by eye is working with a molecule whose effect takes hours to appear.
No source is stored against this line.
What is recorded as being sold
5 marketed supplement labels list this ingredient, classed as non-nutrient/non-botanical and other combinations.
Those labels carry all other and structure/function claims. A claim of that kind is written by the manufacturer and is not assessed by any regulator, so its presence says nothing about whether it is true.
Evidence carries across two names for one substance. It does not carry across a salt, a mirror form or a mixture.
What it would be like to take◇Read from sources, not yet reviewed
What you could measure
Watching one thing carefully can tell you whether it moved. It cannot tell you what moved it.
This is sold without a prescription, so a person can sensibly watch one thing and see whether it moves.
Pick one goal. One goal only. Two at once cannot be told apart afterwards.
Pick one thing to watch. No registered study lists a measure RNAWiki could read for this.
Measure before you start. Take the same measurement several times first. One reading is not a starting point.
Know the swing. Write down how much it moves on its own across a normal week.
Change one thing. Change nothing else at the same time, including training and sleep.
Give it the study length. No finished study window is recorded, so no length is suggested here.
Track whether you took it. Missed days are the most common reason a home test shows nothing.
Read the trend. Look at the line across weeks. A single reading tells you almost nothing.
What not to measure
Anything that swings more day to day than the change you are looking for.
A wearable estimate of sleep stages, which is an estimate and not a measurement.
Weight on one morning, which mostly records water.
A feeling you did not write down before starting.
When to stop
Stop if something new and unpleasant starts, and ask a pharmacist or doctor.
Stop if you cannot keep everything else steady, because the result will not mean anything.
Stop at the end of the window you set, and read the trend then.
Tracking can show whether something changed for you. It cannot show what caused it.
RNAWiki does not work out an amount for anyone.
What is missing or unclear◇Read from sources, not yet reviewed
Claims that go past the evidence
Things said about this substance that sound reasonable, and the exact step that is missing between the evidence and the claim.
✗Goes past the evidence
That the post-2015 rise in reported exposures measures a rise in use rather than the introduction of a coding term
Why it sounds right. It follows from something real on this page: a body step, an animal result or a related finding.
The missing step. Nobody measured this in people for this use, or the study that did measure it did not show it.
What would change this
A study in people, for this exact use, measuring this exact thing, that a reviewer signs off.
RNAWiki has not yet published a reviewed conclusion for this use.
✗Goes past the evidence
That approval as a prescription anxiolytic in post-Soviet states describes the exposure obtained from a US bulk-powder product
Why it sounds right. It follows from something real on this page: a body step, an animal result or a related finding.
The missing step. Nobody measured this in people for this use, or the study that did measure it did not show it.
What would change this
A study in people, for this exact use, measuring this exact thing, that a reviewer signs off.
RNAWiki has not yet published a reviewed conclusion for this use.
✗Goes past the evidence
That phenibut is simply "a GABA-B drug" — the active enantiomer binds α2-δ four times more tightly, and its antinociceptive effect survives GABA-B blockade
Why it sounds right. It follows from something real on this page: a body step, an animal result or a related finding.
The missing step. Nobody measured this in people for this use, or the study that did measure it did not show it.
What would change this
A study in people, for this exact use, measuring this exact thing, that a reviewer signs off.
RNAWiki has not yet published a reviewed conclusion for this use.
✗Goes past the evidence
That a negative hospital toxicology screen excludes phenibut; no routine panel contains it
Why it sounds right. It follows from something real on this page: a body step, an animal result or a related finding.
The missing step. Nobody measured this in people for this use, or the study that did measure it did not show it.
What would change this
A study in people, for this exact use, measuring this exact thing, that a reviewer signs off.
RNAWiki has not yet published a reviewed conclusion for this use.
What is missing or unclear◇Read from sources, not yet reviewed
What nobody knows yet
Open questions, each with why it is open and what would close it.
Missing populations
Which groups were under-represented in the studies has not been recorded.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Missing long-term data
No completed tested study window is recorded.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
No reviewed conclusion
RNAWiki has not yet published a reviewed conclusion for this use.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Missing interaction studies
No interaction was found in the registers checked. Not finding one is not the same as showing there is none.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Formulation uncertainty
Several salts, forms or products of Phenibut are recorded. Results from one form may not transfer to another.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Mechanism not reviewed
No reviewed mechanism story exists for this substance.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
What happened in people◇Read from sources, not yet reviewed
Check any of this yourself
Every line above traced back to the study it came from. This is the technical layer, and the vocabulary changes here.
Every line above can be traced to the study named beside it. Follow the link and read it.
1,320 exposures in all 50 states, coma in 6.2%, three deaths
In plain words
Across eleven years, US poison centres logged 1,320 phenibut exposures from every state. Eight in a hundred reached life-threatening severity, eighty people were comatose, and three died.
What was measured
Exposure count, demographics, clinical effects and outcome severity across 1,320 phenibut exposures, 2009-2019
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Graves et al. analysed National Poison Data System records for 2009 to 2019: 1,320 phenibut exposures from all 50 states and the District of Columbia, with 1,122 (85.0%) of calls originating from health-care facilities. 58.4% of exposures were in adults aged 18 to 34 (mean 31.7 years, SD 13.1) and 75.5% were male. Cases rose sharply from 2015, when poison centres gained the ability to code "phenibut" as a term — a coding change that partly confounds the trend and which the authors state. Formulations were solids in 65.1% and powder in 24.8%; 93.2% were ingestions. Reported effects were agitation 30.4%, drowsiness or lethargy 29.0%, tachycardia 21.9% and confusion 21.3%. Coma occurred in 80 cases (6.2%), including one adolescent. Half of cases (49.6%) had moderate effects; major effects — life-threatening or causing significant disability — occurred in 12.6%, and three deaths were reported. Among exposures where phenibut was the only agent involved, 10.2% had major effects, including one death.
Written into the record, not signed off as a reviewed claim
FDA warned that it did not belong in supplements, and the doses went up
In plain words
After the FDA said phenibut is not a permitted supplement ingredient, researchers re-tested the same four brands. Two that had contained none now contained it, and three of the four had more than before — up to 1,164 mg a serving.
What was measured
Phenibut content per serving in four supplement brands before and after FDA warnings, by LC-TOF-MS isotope dilution
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Cohen et al. selected four brands of dietary supplements labelled as containing phenibut that were on sale both before and after the FDA warnings, and analysed them by liquid chromatography time-of-flight mass spectrometry with isotope-dilution quantification. Before the warnings, two of the four contained phenibut, at 484 mg and 487 mg per serving. After the warnings, all four contained it, at 21 mg to 1,164 mg per serving; phenibut was first detected only after the warnings in two brands, and the quantity increased in three of the four. Quantities per dose reached as much as 450% greater than a typical 250 mg pharmaceutical tablet manufactured in Russia. The conclusion shift recorded here is not scientific but regulatory: an advisory intended to remove a substance from a market coincided with more of it appearing in the same products, which is a measurable outcome of a regulatory action and is recorded as such.
Written into the record, not signed off as a reviewed claim
It binds the gabapentin target more tightly than the baclofen target
In plain words
Phenibut is usually described as a GABA-B drug like baclofen. In a direct binding comparison, the active enantiomer bound the calcium-channel subunit that gabapentin targets about four times more tightly than it bound GABA-B.
What was measured
Ki at the α2-δ subunit for R-phenibut, S-phenibut, baclofen and gabapentin, with GABA-B antagonist control in a functional pain model
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Zvejniece et al. measured binding affinity for the α2-δ subunit of the voltage-dependent calcium channel using radiolabelled gabapentin in rat brain membranes: Ki was 23 µM for R-phenibut, 39 µM for S-phenibut, 156 µM for baclofen and 0.05 µM for gabapentin. R-phenibut's α2-δ affinity was about four times higher than its affinity for GABA-B. In the formalin-induced paw-licking test, pre-treatment with R-phenibut dose-dependently reduced the nociceptive response in both phases, and that effect was not blocked by the GABA-B-selective antagonist CGP35348 — attributing it to α2-δ rather than to GABA-B. Both enantiomers alleviated mechanical and thermal allodynia after chronic constriction injury of the sciatic nerve. R-phenibut did not affect pentylenetetrazole-induced seizures at doses up to 100 mg/kg. Note the absolute numbers: phenibut is a micromolar ligand at both targets while gabapentin is nanomolar at α2-δ, which is why phenibut is dosed in hundreds of milligrams.
Written into the record, not signed off as a reviewed claim
One in five patients in a regional series required intubation
In plain words
A Minnesota poison-centre review found 56 phenibut cases over nineteen years, 48 of them in the last five. Eleven of the 56 needed a breathing tube. None died.
What was measured
Intubation rate, clinical effects and reason for use across 56 phenibut exposures to one regional poison centre, 2000-2018
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
McCabe et al. reviewed all phenibut exposure calls to the Minnesota Poison Control System from January 2000 through December 2018: 56 calls, of which 48 (85.7%) fell in the final five years. More than half of patients had central nervous system effects and 10.7% had withdrawal concerns. Abuse was the stated reason for use in 27 patients (48%) and treatment of anxiety in 13 (23%). Co-ingestants were documented in 35.7%. No patient died, but 11 (19.6%) were intubated. The authors conclude that clinicians should expect CNS and respiratory depression and be prepared to manage the airway. A single-state series of 56 is small, and its value is the intubation proportion — a hard endpoint that does not depend on how a poison-centre outcome category was coded.
Written into the record, not signed off as a reviewed claim
It is baclofen without the chlorine
In plain words
Baclofen is a prescription-only muscle relaxant whose withdrawal can cause seizures and delirium. Phenibut is the same molecule minus one chlorine atom, and it is sold in tubs.
What was measured
Structural and pharmacological relationship between phenibut and baclofen, with comparative α2-δ binding affinities
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Phenibut is β-phenyl-γ-aminobutyric acid; baclofen is β-(4-chlorophenyl)-γ-aminobutyric acid. The chlorine substitution raises GABA-B potency substantially — baclofen is the clinical GABA-B agonist for exactly that reason — but the pharmacological class is the same, and the α2-δ binding comparison in the Zvejniece series put both compounds in the same micromolar range at that second target. Baclofen requires a prescription in the United States and carries a recognised withdrawal syndrome that can include seizures, hallucinations and autonomic instability. Phenibut requires nothing. The structural relationship is the most economical explanation of the withdrawal syndrome described in the case literature, and it is the reason baclofen itself is used to manage phenibut withdrawal in some reported cases.
Written into the record, not signed off as a reviewed claim
The 2015 rise in reported cases is partly a coding change
In plain words
Phenibut cases appear to jump sharply from 2015. That is the year poison centres were first able to record "phenibut" as a term, so part of the increase is the counting, not the drug.
What was measured
That the post-2015 rise in reported phenibut exposures measures a rise in phenibut use rather than a change in how exposures were coded
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
The MMWR analysis states that the number of cases increased sharply over 2009-2019, particularly since 2015, when regional poison centres became able to use "phenibut" as a relevant term to capture exposures. A surveillance series whose case-ascertainment method changes mid-period cannot separate a real increase from an improvement in detection, and the authors say so. The independent Minnesota series shows the same shape — 48 of 56 calls in the final five years — which is consistent with a genuine rise, but that series covers the same period and is subject to the same coding change. The honest statement is that phenibut exposures rose over the decade and that the size of the rise is not measurable from these data.
Written into the record, not signed off as a reviewed claim
Routine drug screens do not detect it
In plain words
A person in coma or in withdrawal from phenibut will have a clean hospital toxicology screen, because nothing in the standard panel looks for it.
What was measured
Requirement for a targeted chromatographic method rather than routine immunoassay to identify phenibut exposure
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Phenibut is not an analyte in standard hospital immunoassay drug-of-abuse panels, and its identification requires a targeted chromatographic method. The clinical consequence is visible in the case literature: presentations of unexplained coma, agitated delirium or an unfamiliar withdrawal syndrome in young adults with negative screens. The regional series found abuse as the stated reason for use in 48% of cases and withdrawal concerns in 10.7%, with 19.6% intubated — a clinical picture severe enough to demand an explanation that the available test does not supply. This is a measured property of the analytical system rather than of the drug, and it is the reason the workflow on this page ends with a targeted plasma method rather than a screen.
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What is not here
8 questions this page could not answer
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What it may clash with — found nothing in the sources checked.
Other ways to the same goal — found nothing in the sources checked.
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The record as stored
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The older medicine-wide conclusion held in this record
Written for a clinical reader, and about the medicine as a whole rather than about one indication, population and set of trials. RNAWiki does not treat it as a programme conclusion and no reviewer has signed it off in that form. It is here word for word because it is what the record holds.
A GABA-B agonist one chlorine atom away from baclofen, sold in US supplements at up to 1,164 mg per serving — more than four times a Russian pharmaceutical tablet — with 1,320 poison-centre exposures across all 50 states in eleven years, coma in 6.2% and three deaths.
Recorded evidence blocks (0)
Where it is registeredIdentifiers, relations and other names
Fenibut, Anvifen, Noofen — prescription products in Russia, Latvia, Ukraine and Kazakhstan. In the United States it is sold in supplements under names such as Fenibut and β-phenyl-GABA
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This is a record of evidence. It is not medical advice, and it does not say this substance suits you. Nothing here says any substance on RNAWiki is appropriate for a child.