EmergingResearch compound

F‑Phenibut

Fluorinated Phenibut, more potent, more lipophilic GABA-B agonist variant.

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WHAT IS F-PHENIBUT?

Detailed overview

Fluorophenibut is an unofficial analog produced by para-fluoro substitution on the phenyl ring of Phenibut. Increased lipophilicity yields faster blood-brain-barrier penetration and **roughly 3-5× higher in vivo potency** (correspondingly ~50-100 mg active dose instead of 200-400 mg), but proportionally **higher tolerance and dependence risk**. No clinical trials exist, only a safety profile extrapolated from Phenibut`s pharmacology. ⚠️ The withdrawal syndrome can be more severe than Phenibut withdrawal → ER-level treatment cases documented. **Schedule II controlled in Alabama and Michigan (USA)**; banned in the UK under the Psychoactive Substances Act. Legal grey zone in other EU member states, sold as a "research chemical".

Mechanism

GABA-B agonist (Phenibut-like)

Half-life

No validated human data

Legal status

Not approved anywhere

Safety

Side effects, stop signs, contraindications

Side effects · 6

  • Sedation, drowsiness, impaired motor coordination
  • Rapidly developing tolerance, even after a few days of daily use
  • Physical dependence and severe withdrawal (anxiety, insomnia, tremor), potentially worse than phenibut
  • Rebound anxiety and irritability as the effect wears off
  • Hangover-like fatigue and cognitive dullness (brain fog)
  • Nausea, dizziness; at overdose respiratory depression and altered consciousness

Contraindications · 6

  • Pregnancy and breastfeeding
  • Combined with alcohol or other CNS depressants (benzodiazepines, opioids, gabapentinoids): life-threatening sedation and respiratory depression
  • History of substance use disorder or addiction (high dependence potential)
  • Abrupt discontinuation after prolonged use is contraindicated: gradual taper needed to avoid severe withdrawal
  • Driving and operating machinery should be avoided during the effect due to sedation
  • No validated human safety data, not an approved drug: long-term effects unknown, avoid without clinical supervision

Related Nootropics

Same therapeutic category

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MolekulaX Editorial Team·Source-verified · PubMed · FDA · EMA
Updated: June 19, 2026

The information here is strictly for educational and scientific purposes. It does not replace medical advice or clinical consultation, and it does not encourage illegal substance or pharmaceutical use. Data is sourced. When in doubt, consult your doctor.