Phenibut
Also known as: beta-Phenyl-GABA, Noofen, Citrocard, Phenyl-GABA
GABA-B Agonist | Anxiolytic & Sleep Aid
Overview
Phenibut (beta-phenyl-gamma-aminobutyric acid) is a synthetic GABA analog developed in the Soviet Union in the 1960s. It was designed to cross the blood-brain barrier, which GABA itself cannot do efficiently, by adding a phenyl ring to the GABA molecule. Phenibut has been prescribed in Russia and several former Soviet states since the 1960s for the treatment of anxiety, insomnia, post-traumatic stress disorder, vestibular disorders, and stuttering. It was famously included in the medical kit of Soviet cosmonauts for its calming effects without impairing cognitive performance. Phenibut is NOT approved by the FDA, EMA, or any Western regulatory agency as a pharmaceutical drug. In the United States, Australia, and parts of Europe, it has been sold as a dietary supplement or nootropic, though several countries have moved to restrict or ban its sale due to growing reports of dependence, withdrawal, and adverse events. The addiction and dependence potential of phenibut is HIGH, and tolerance develops rapidly with repeated use. This compound should be treated with the same caution as benzodiazepines or other GABAergic drugs.
Key benefits
- Reduction of anxiety and social inhibition
- Improved sleep onset and sleep quality
- Mild mood elevation and sense of well-being
- Reduced cognitive effects of stress without heavy sedation at low doses
- Potential benefit for vestibular disorders (clinical use in Russia)
Mechanism of action
Phenibut acts primarily as an agonist at GABA-B receptors, the same receptor target as baclofen (to which it is structurally related). GABA-B receptor activation inhibits neuronal excitability by opening potassium channels and reducing calcium influx at presynaptic terminals, leading to decreased neurotransmitter release and a net inhibitory effect on the central nervous system. This produces anxiolytic, sedative, and muscle-relaxant effects. In addition to GABA-B agonism, phenibut blocks voltage-dependent calcium channels (VDCCs), particularly alpha-2-delta subunit-containing channels, a mechanism shared with gabapentin and pregabalin. This contributes to its anxiolytic and analgesic properties. At higher doses, phenibut may also weakly stimulate GABA-A receptors, contributing to its sedative effects, though this is not its primary mechanism at typical doses. The R-enantiomer of phenibut is responsible for the majority of its GABA-B receptor activity, while the S-enantiomer is more selective for the alpha-2-delta VDCC subunit.
Molecular data
- Type
- Phenyl-substituted GABA analog (C10H13NO2)
- Half-life
- ~5 hours
Indications
What the research community uses this compound for, with self-reported effectiveness.
Neurological / Mood
Other
Dosing protocols
Common protocols by delivery method. Adjust the curve below to model accumulation in your own cycle.
Delivery method
| Protocol | Dose | Frequency | Duration |
|---|---|---|---|
| — | 250-500 mg | Max 1-2x per week, never consecutive days | — |
| — | 500-750 mg | Occasional use only, max 1x per week | — |
| — | 750-1000 mg | Occasional use only, max 1x per week | — |
Safety
Reported adverse effects, contraindications, and what to monitor on cycle.
Common side effects
- Drowsiness and sedation, especially at higher doses
- Dizziness and lightheadedness
- Nausea and gastrointestinal discomfort (particularly with HCl form on empty stomach)
- Tolerance develops rapidly, often within 2-3 days of consecutive use
- Next-day grogginess or hangover-like effects
- Headache
Rare side effects
- Motor incoordination and ataxia at high doses
- Paradoxical agitation or anxiety (rare, dose-dependent)
- Allergic reactions (skin rash, itching)
- Tremor
- Numbness or paresthesias
Contraindications
- History of substance abuse or addiction (phenibut has high abuse potential)
- Concurrent use of alcohol, benzodiazepines, GHB, barbiturates, or other CNS depressants
- Renal impairment (phenibut is primarily excreted by the kidneys)
- Pregnancy and breastfeeding (insufficient safety data)
- History of seizure disorders (withdrawal may lower seizure threshold)
- Current dependence on any GABAergic substance
Monitoring
- Self-monitor frequency of use strictly: never more than 1-2 times per week
- Track any urge to increase dose or frequency as an early sign of dependence
- If daily use has occurred for more than 5-7 days, do NOT stop abruptly. Seek medical guidance for tapering.
- Monitor for rebound anxiety and insomnia between uses
- Observe for signs of tolerance (needing higher doses for the same effect)
References
Primary literature and clinical-trial data informing this entry.