WARNINGMIXING OR WITHDRAWAL CAN BE DANGEROUS
Ordinary doses in combination with other depressants can fatally stop breathing. After prolonged regular use, stopping suddenly can also cause seizures or delirium; seek medical help.
F-Phenibut
F-Phenibut is a central nervous system depressant of the gabapentinoid class and a close structural analog of both phenibut and baclofen. It is a derivative of the neurotransmitter GABA1, featuring a fluorine-substituted phenyl group1 that allows it to cross the blood-brain barrier. Compared to phenibut, it is reported to have a faster onset, significantly greater potency1, and shorter duration. Very little is known about its toxicity or addiction potential.
Dosage & Duration
Dosage
Doses are population estimates that vary widely between individuals.
Duration
Subjective Effects
The experience closely resembles that of phenibut, reflecting the compound's shared mechanism as a GABAB receptor agonist, but arrives with greater potency owing to the fluorine substitution. It is a predominantly depressant and anxiolytic state with little in the way of sensory alteration, characterized by relief from anxiety, easy sociability, and physical relaxation that deepens into sedation as the dose increases.
Physical
Muscle relaxation and a relaxed, heavy body feeling are the primary physical effects, progressing to sedation and impaired coordination at higher doses.
Depressant
Cognitive
The headspace is calm and disinhibited, with social ease and a mild sense of well-being replacing anxious thought patterns rather than any pronounced intoxication at lower doses.
Emotional
Social
Pharmacology
Pharmacodynamics
F-Phenibut acts as an agonist of the GABA-B receptor1 with selectivity over the GABA-A receptor. It is less potent than baclofen at the GABA-B receptor but more potent than phenibut.1 F-Phenibut may also bind to the α2δ-1 subunit of voltage-gated calcium channels in a manner similar to other gabapentinoids, which could reduce the release of several excitatory neurotransmitters including glutamate, substance P, acetylcholine, and norepinephrine.
Pharmacokinetics
Interactions
An unlisted combination is an unknown one, not a safe one. Check a dedicated combination chart before mixing.
Tolerance
Tolerance timelines are rules of thumb, not exact schedules, and vary widely between individuals and use patterns.
GABAergic depressants, Phenibut and related analogues
Harm Potential
Addiction & Dependence
Psychological
ModerateModerately psychologically addictive, particularly with heavy or frequent use. The rapid onset compared to phenibut facilitates compulsive redosing, which is reported to be highly pronounced. The combination of reduced inebriation with greater euphoria relative to other GABAergic depressants contributes to elevated abuse potential.
Physical
ModeratePhysical dependence can develop with regular use over several weeks or longer.2 Withdrawal symptoms may include severe anxiety, nervousness, tremors, agitation, rapid heartbeat, fatigue, nausea, vomiting, and insomnia. Gradual dose reduction is recommended to avoid withdrawal effects.
Psychosis Risk
Psychosis is reported as a potential withdrawal symptom following cessation of prolonged or heavy use2, similar to phenibut. Not typically associated with acute intoxication at standard doses.
History & Culture
F-Phenibut, designated by the developmental code name CGP-11130, is a GABA analogue that was investigated as a potential pharmaceutical agent but was never marketed.[cite:pubchem-ncbi-nlm-nih-gov-neue-psychoaktive-stoffe-gesetz-npsg-1-4-and-current-anlage-1-nr-1-anlage-1-source-bgbl-2025-i-nr-292-cu…
Legality
By Country
References
Citations
- Irie, T., Yamazaki, D., & Kikura-Hanajiri, R.. (2020-10-05). F-phenibut (β-(4-Fluorophenyl)-GABA), a potent GABAB receptor agonist, activates an outward-rectifying K+ current and suppresses the generation of action potentials in mouse cerebellar Purkinje cells. European Journal of Pharmacology, 884, 173437. https://doi.org/10.1016/j.ejphar.2020.1734371234567
- Kain, Kevin M., Glenn, J., & Koefed, A.. (2024). Case Report: Management of F-Phenibut Withdrawal. Royal College of Psychiatrists International Congress 2024. https://www.postersessiononline.eu/173580348_eu/congresos/RCPSych2024/aula/-P_808_RCPSych2024.pdf12
- NIH PubChem Compound 103611, 4-Fluorophenibut. pubchem.ncbi.nlm.nih.gov (n.d.). https://pubchem.ncbi.nlm.nih.gov/compound/103611123
- Cgp-11130 (PD130882). Probes & Drugs (2026). https://www.probes-drugs.org/compound/PD130882/1
- Production Convex substanceIndex live row for f-phenibut. glad-minnow-656.convex.cloud (n.d.). https://glad-minnow-656.convex.cloud123
- BtMG § 1, official consolidated text. gesetze-im-internet.de (n.d.). https://www.gesetze-im-internet.de/btmg_1981/__1.html1
- BtMG Anlage I, official current list. gesetze-im-internet.de (n.d.). https://www.gesetze-im-internet.de/btmg_1981/anlage_i.html1
- NpSG, official consolidated text and current amendment status. gesetze-im-internet.de (n.d.). https://www.gesetze-im-internet.de/npsg/BJNR261510016.html1
- NpSG Anlage 1, current generic substance-group definitions. gesetze-im-internet.de (n.d.). https://www.gesetze-im-internet.de/npsg/anlage_1.html1
- NpSG § 3, official prohibition and exceptions. gesetze-im-internet.de (n.d.). https://www.gesetze-im-internet.de/npsg/__3.html1
- AMG § 2, official medicinal-product definition. gesetze-im-internet.de (n.d.). https://www.gesetze-im-internet.de/amg_1976/__2.html1
- AMG § 5, official prohibition of unsafe medicinal products. gesetze-im-internet.de (n.d.). https://www.gesetze-im-internet.de/amg_1976/__5.html1
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- 2025. évi XIX. törvény on amendments concerning the prohibition of drug production, use, distribution and promotion. njt.jog.gov.hu (n.d.). https://njt.jog.gov.hu/jogszabaly/2025-19-00-00.01
- 2012. évi C. törvény (Btk.), current consolidated Hungarian Penal Code. njt.jog.gov.hu (n.d.). https://njt.jog.gov.hu/jogszabaly/2012-100-00-001
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- Lithuanian Criminal Code No. VIII-1968, current consolidated text, Articles 259–260. e-seimas.lrs.lt (n.d.). https://e-seimas.lrs.lt/rs/actualedition/TAIS.111555/BNjOlHflTR/1
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- Schutz vor Designerdrogen: Weitere psychoaktive Stoffe verboten. swissmedic.ch (n.d.). https://www.swissmedic.ch/swissmedic/de/home/news/mitteilungen/schutz-vor-designerdrogen.html1
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Automated synthesisInformation aggregated and synthesized using an autonomous workflow built by Josie Kins.
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