Phenibut: Chemical Profile, CAS Number, Pharmacology & Toxicology

Phenibut is a synthetic gamma-aminobutyric acid analogue commonly described in scientific literature as beta-phenyl-GABA. It is studied in chemistry, pharmacology, toxicology, forensic science, and analytical research because of its structural relationship to GABA and its documented public-health concerns.

This Phenibut chemical profile reviews its CAS number, molecular formula, IUPAC name, structure, high-level pharmacology, analytical identification methods, toxicology overview, and regulatory considerations.

This article is for educational and scientific reference only. It does not provide dosage information, use instructions, sourcing guidance, synthesis methods, or medical advice.

General Information

Property	Value
Chemical Name	Phenibut
Common Synonyms	Fenibut, PhGABA, Phenyl-GABA, beta-phenyl-GABA
CAS Number	1078-21-3
PubChem CID	14113
Molecular Formula	C10H13NO2
Molecular Weight	179.22 g/mol
IUPAC Name	4-amino-3-phenylbutanoic acid
Chemical Class	Synthetic GABA analogue
Related Salt Form	Phenibut hydrochloride / 4-amino-3-phenylbutyric acid hydrochloride
HCl Salt Formula	C10H14ClNO2
Research Context	Pharmacology, toxicology, analytical chemistry, forensic chemistry

PubChem lists phenibut as CID 14113 with molecular formula C10H13NO2, molecular weight 179.22 g/mol, CAS number 1078-21-3, and the IUPAC name 4-amino-3-phenylbutanoic acid. PubChem also lists 4-amino-3-phenylbutyric acid hydrochloride separately with formula C10H14ClNO2 and CID 11499499.

Chemical Identity

Phenibut is structurally related to gamma-aminobutyric acid, commonly known as GABA. The molecule includes a phenyl group attached to a GABA-like backbone, which is why it is often called beta-phenyl-GABA.

Chemical identity should be verified carefully because phenibut may appear under several names, including fenibut, PhGABA, Phenyl-GABA, and 4-amino-3-phenylbutanoic acid.

For accurate documentation, researchers should compare:

• CAS number
• IUPAC name
• Molecular formula
• Molecular weight
• Salt form
• Synonyms
• Structure
• Safety Data Sheet
• Certificate of Analysis
• Analytical method records

This is especially important when distinguishing phenibut free base from phenibut hydrochloride.

Chemical Structure Overview

Phenibut contains several important structural features:

• Amino group
• Carboxylic acid group
• Phenyl ring
• GABA-like carbon chain
• Chiral center
• Beta-phenyl substitution

The phenyl ring is the key feature that distinguishes phenibut from GABA. Scientific reviews describe phenibut as beta-phenyl-GABA and discuss its structure-activity relationship in comparison with related GABA analogues such as baclofen.

Phenibut vs GABA

Phenibut is related to GABA, but it is not the same compound.

GABA is an endogenous inhibitory neurotransmitter. Phenibut is a synthetic analogue with a phenyl group added to the GABA-like structure.

Compound	General Identity
GABA	Endogenous gamma-aminobutyric acid
Phenibut	Synthetic beta-phenyl-GABA analogue
Baclofen	Chlorinated GABA-related compound
4-Fluorophenibut	Fluorinated phenibut analogue
Phenibut HCl	Hydrochloride salt form of phenibut

This distinction matters because related GABA analogues may differ in receptor activity, pharmacology, analytical behavior, toxicology, and regulatory treatment.

Free Base vs Hydrochloride Salt

Phenibut may be discussed as the free base or as a hydrochloride salt.

Phenibut free base has the formula:

C10H13NO2

The hydrochloride salt form is commonly represented as:

C10H14ClNO2

These forms should not be treated as identical in chemical documentation. They may differ in molecular weight, database record, physical properties, solubility behavior, supplier documentation, SDS records, and COA records.

For scientific accuracy, researchers should confirm whether a record refers to phenibut free base, phenibut hydrochloride, or another related form.

Discovery and Historical Background

Phenibut has been discussed in scientific literature for decades, especially in relation to Soviet and Russian pharmacology. A widely cited review by Lapin describes phenibut as beta-phenyl-GABA and compares its structure and pharmacological activity with related compounds.

In modern scientific writing, phenibut appears in several contexts:

• Pharmacology research
• Toxicology reports
• Poison center data
• Forensic toxicology
• Dietary supplement regulatory discussions
• Analytical chemistry
• Public-health surveillance

Because phenibut has appeared in products marketed as dietary supplements, it also has a notable regulatory and public-health history.

Pharmacology Overview

Phenibut is commonly described as a GABA analogue. Scientific literature has discussed activity related to GABA receptor systems and related pharmacological targets. A 2019 review describes phenibut as a glutamic acid derivative with activity involving GABA-related receptor systems and beta-phenethylamine receptors.

At a high level, phenibut is relevant to research areas involving:

• GABA-related pharmacology
• Central nervous system depressant effects
• Structure-activity relationships
• GABA analogue comparison
• Toxicology of psychoactive substances
• Dependence and withdrawal literature
• Forensic detection

This article does not provide clinical instructions, dosage guidance, or use recommendations.

Mechanism of Action

Phenibut’s pharmacology is usually discussed in relation to GABA-related receptor activity. It is structurally related to GABA, and scientific reviews compare it with baclofen and other GABA analogues.

For educational purposes, the mechanism can be summarized as follows:

Phenibut is a synthetic GABA analogue whose pharmacological relevance is linked to GABA-related signaling systems and related central nervous system activity.

Detailed receptor pharmacology should be discussed cautiously because phenibut has misuse potential and has been associated with toxicity, dependence, and withdrawal reports.

Laboratory and Research Applications

Phenibut may be relevant in legitimate laboratory and scientific contexts, especially where researchers study chemical identity, toxicology, or analytical detection.

Examples include:

• Forensic toxicology research
• Analytical method development
• LC-MS identification studies
• GC-MS detection research
• Reference material comparison
• Poison center trend analysis
• Public-health surveillance
• GABA analogue structure-activity research
• Toxicology literature review
• Regulatory science

These contexts are scientific and educational. They should not be presented as product-use, self-experimentation, or purchase-oriented content.

Analytical Identification

Phenibut can be evaluated using analytical chemistry methods depending on the research goal, sample type, and matrix.

Relevant analytical approaches may include:

• LC-MS
• GC-MS
• HPLC
• NMR spectroscopy
• FTIR spectroscopy
• Reference standard comparison
• Targeted toxicology screening
• High-resolution mass spectrometry

Forensic and toxicology laboratories may use mass spectrometry-based methods when detecting phenibut or related compounds in complex samples.

A reliable identity workflow should compare more than one field:

• CAS number
• Molecular formula
• Molecular weight
• IUPAC name
• Salt form
• Retention behavior
• Spectral data
• Reference material data
• Source documentation

Toxicology Overview

Phenibut has a significant toxicology literature. Clinical and public-health reports describe toxicity, dependence, and withdrawal concerns.

A 2023 systematic review of phenibut toxicity and withdrawal case reports found that commonly reported toxicity presentations included altered mental status, somnolence, psychosis, and movement disorders.

CDC’s MMWR reported 1,320 phenibut exposure calls to U.S. poison centers during 2009–2019, with calls reported from all 50 states and the District of Columbia. Most calls originated from health care facilities.

A scientific toxicology overview may consider:

• Exposure context
• Co-exposures
• Product labeling issues
• Central nervous system effects
• Withdrawal reports
• Poison center trends
• Forensic detection
• Regulatory actions
• Analytical confirmation

This article does not provide treatment advice. Suspected exposure or withdrawal concerns should be handled by qualified medical or toxicology professionals.

Phenibut in Public-Health Reporting

Phenibut is important in public-health literature because it has appeared in online and supplement-market contexts despite regulatory concerns.

CDC reported increasing poison center attention to phenibut exposures in the United States between 2009 and 2019. FDA has also stated that phenibut does not meet the statutory definition of a dietary ingredient under the Federal Food, Drug, and Cosmetic Act.

This makes phenibut a strong candidate for neutral scientific education. Articles should focus on chemical identity, toxicology, analytical detection, and regulation rather than consumer use.

Regulatory Considerations

Phenibut’s regulatory status varies by jurisdiction. In the United States, FDA states that phenibut does not meet the statutory definition of a dietary ingredient, and dietary supplements declaring phenibut as a dietary ingredient are misbranded. FDA also issued warning letters in 2019 to companies marketing dietary supplements labeled to contain phenibut.

For neutral scientific writing, regulatory sections should avoid giving legal advice. Instead, they should direct researchers to verify:

• Country-specific law
• State or regional restrictions
• Institutional policy
• Supplier documentation
• SDS records
• Import/export rules
• Laboratory safety requirements
• Regulatory agency updates

Regulatory status should not be assumed from a chemical name, database listing, or online product label.

Phenibut and Dietary Supplement Concerns

Phenibut has been found in products marketed as dietary supplements. FDA’s position is that phenibut is not a lawful dietary ingredient under the FD&C Act, and products declaring it as a dietary ingredient are misbranded.

Information-Gain Note: Phenibut Is Not Just “GABA With a Phenyl Ring”

A basic article may say that phenibut is simply GABA with a phenyl group. That is true structurally, but it is not enough for scientific accuracy.

Phenibut should be discussed as a distinct chemical entity with its own CAS number, stereochemistry, salt forms, pharmacology, toxicology literature, and regulatory issues.

For accurate chemical documentation, researchers should verify:

• Whether the material is free base or hydrochloride salt
• CAS number and molecular formula
• IUPAC name and synonyms
• Stereochemical considerations
• SDS and COA records
• Analytical method data
• Jurisdiction-specific regulatory status
• Toxicology and public-health literature

This gives the article more value than a simple synonym-based chemical summary.

Common Misunderstandings About Phenibut

Phenibut is often misunderstood because it appears in overlapping contexts: chemistry, pharmacology, supplements, toxicology, and online markets.

Common misunderstandings include:

• Treating phenibut and GABA as the same compound
• Treating phenibut free base and phenibut hydrochloride as identical
• Assuming online availability means regulatory approval
• Assuming supplement labeling means lawful dietary ingredient status
• Ignoring poison center and toxicology reports
• Confusing chemical identity with safety
• Treating anecdotal reports as scientific evidence
• Assuming legal status is the same everywhere

A responsible chemical profile should separate identity, pharmacology, toxicology, and regulation.

Frequently Asked Questions

What is phenibut?

Phenibut is a synthetic GABA analogue also known as beta-phenyl-GABA. It is studied in pharmacology, toxicology, forensic science, and analytical chemistry.

What is the CAS number for phenibut?

The CAS number for phenibut free base is 1078-21-3.

What is the molecular formula of phenibut?

The molecular formula of phenibut free base is C10H13NO2.

What is the molecular weight of phenibut?

PubChem lists phenibut with a molecular weight of 179.22 g/mol.

What is the IUPAC name of phenibut?

The IUPAC name is 4-amino-3-phenylbutanoic acid.

Is phenibut the same as GABA?

No. Phenibut is structurally related to GABA, but it is a distinct synthetic compound.

Is phenibut hydrochloride the same as phenibut free base?

No. Phenibut hydrochloride is a salt form and should be documented separately from the free base.

Why is phenibut relevant to toxicology?

Phenibut is relevant to toxicology because clinical reports and poison center data describe toxicity and withdrawal concerns.

Is phenibut a legal dietary supplement ingredient in the United States?

FDA states that phenibut does not meet the statutory definition of a dietary ingredient, and dietary supplements that declare phenibut as a dietary ingredient are misbranded.

What analytical methods may be used to identify phenibut?

Analytical methods may include LC-MS, GC-MS, HPLC, NMR, FTIR, and reference standard comparison, depending on the research context.

Does this article provide dosage or use guidance?

No. This article is for educational and scientific reference only. It does not provide dosage, administration, sourcing, or use instructions.

Why should researchers verify phenibut documentation carefully?

Researchers should verify documentation because phenibut can appear under multiple synonyms, salt forms, database records, and regulatory categories.

References

• PubChem Phenibut
• PubChem 4-Amino-3-phenylbutyric acid hydrochloride
• FDA Phenibut in Dietary Supplements
• CDC MMWR Phenibut Exposures Reported to Poison Centers
• PubMed clinical review literature on phenibut toxicity and withdrawal
• PubMed review literature on beta-phenyl-GABA pharmacology