This is an experience report concerning 4F-Phenibut (Fluorobut). I have experimented with 4F-Phenibut and Phenibut occasionally (without ever creating tolerance) over the past several years.
4-Fluorophenibut
Limited data
Limited data
Sparse data. Doses and effects may be unreliable or untested.
- 3 corroborating sources
- 1 ROA with full dose ladder
- duration data present
- toxicity data (PsychonautWiki)
- classified Tentative
- classified Research-chemical
- dose data not in PW/TripSit (unverifiable)
- dose ladder unverifiable and undisclosed — capped
Limited data
Sparse data. Doses and effects may be unreliable or untested.
- 3 corroborating sources
- 1 ROA with full dose ladder
- duration data present
- toxicity data (PsychonautWiki)
- classified Tentative
- classified Research-chemical
- dose data not in PW/TripSit (unverifiable)
- dose ladder unverifiable and undisclosed — capped
Aliases: Baflofen, Fluorobut, Cgp-11130, F-phenibut, Fluorophenibut
Summary
4-Fluorophenibut (F-phenibut) is a depressant and anxiolytic GABA analogue, chemically a fluorinated analog of phenibut. It acts primarily as a potent GABA-B receptor agonist, in this respect resembling baclofen more than phenibut, with possible voltage-gated calcium channel activity. It is reported to be 5-10 times more potent than phenibut, with faster onset and shorter duration. Users report more pronounced physical effects and euphoria compared to phenibut, along with a correspondingly higher risk of dependence and compulsive redosing.
Dose Information
| ROA | Light | Common | Strong | Heavy |
|---|---|---|---|---|
| Oral | 100-150mg | 150-400mg | 400-600mg | 600mg+ |
Light
Common
Strong
Heavy
Onset, Duration & After-effects
| ROA | Onset | Comeup | Peak | Offset | Total |
|---|---|---|---|---|---|
| Oral | 20-90 min | 30-60 min | 2-5 hrs | 2-4 hrs | 8-12 hrs |
Import into PsychonautWiki Journal
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Ranges are harm-reduction guidance, not a prescription.
Tolerance
Build-up
develops over 1–4 weeks of regular use
Reset
days to weeks depending on duration of use
Tolerance Decay
Full tolerance
3d
Half tolerance
7d
Baseline
~14d
Acute tolerance: develops within a single session — the reset numbers above apply after sustained heavy use, not after one binge. Within-session tachyphylaxis usually resets largely overnight.
Community experience suggests tolerance accrues rapidly with consecutive-day use and decays over 1–3+ weeks; figures are indicative only and not clinically validated.
Effects
Aggregated from 7 Erowid experience reports
Positive Effects 8
Euphoria
57.1%
70%
Focus Enhancement
57.1%
70%
Anxiety Suppression
57.1%
70%
Color Enhancement
42.9%
70%
Music Enhancement
42.9%
70%
Stimulation
42.9%
70%
Sedation
42.9%
70%
Empathy
42.9%
70%
Adverse Effects 0
Community Trip Reports
Anecdotal first-person accounts from Reddit, Erowid, and Bluelight. Click a source to expand. Reports are harm-reduction context, not medical guidance. Tags summarise each author's own verdict — how reports are classified.
Erowid 3 reports 1 neutral 2 cautionary visit
This is a report for first-time use of a new gabaergic research chemical, F-Phenibut (CAS 52237-19-1). This is a derivative of Phenibut fluorinated at the para- or 4 position of the phenyl ring. It is very similar in structure to Baclofen, substituting a fluorine atom in the place of chlorine.
I just got a new job, but I was having a hard time being my usual relaxed, joking-around self around my coworkers for some reason. Never having used either substance before, I was doing a bit of research on Phenibut and Fluorophenibut/F-phenibut, deciding which to choose for a first time experience.
4-Fluorophenibut's nerd page
Pharmacology, chemical data, effect profiles, and more
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