Phenibut (beta-Phenyl-GABA)
Synthetic GABA-B receptor agonist with some GABA-A activity, originally developed in Russia for cosmonauts. Crosses blood-brain barrier unlike GABA itself due to phenyl group. Largely excreted unchanged (~63% in urine). HIGH ADDICTION POTENTIAL with severe withdrawal syndrome (seizures, psychosis, delirium). Not FDA-approved. Do NOT use daily or combine with other depressants.
Projected serum levels — 500 mg, once daily
Maintenance schedule: 500 mg once daily (oral).
Modeled steady state after ~1 days: peak ≈ 203 mg, trough ≈ 1.4 mg body load. Population-based estimate over 15 days for a 500 mg dose at a 70 kg reference body mass — the interactive app scales curves to your doses, timing, and body mass.
Key facts
- Category
- GABAergic
- Route modeled
- Oral
- Model confidence
- inferred
- Half-life
- 5.3 h
- Common dose
- 500 mg
- Suggested maximum
- 1.5k mg/day
- Reference dose range
- 250–1.5k mg (single dose)
- Suggested cadence
- once daily
Documented interactions
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danger
1,4-BDO (1,4-Butanediol) + Phenibut (beta-Phenyl-GABA)
1,4-BDO converts to GHB. Phenibut is also a GABA-B agonist with a very long half-life (~5h); combined GABA-B agonism produces severe respiratory depression and prolonged unconsciousness.
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danger
Ethanol (Alcohol) + Phenibut (beta-Phenyl-GABA)
Phenibut and alcohol are both CNS depressants acting on GABA receptors. Combined use dramatically increases risk of respiratory depression, loss of consciousness, and death.
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danger
Gabapentin (Neurontin) + Phenibut (beta-Phenyl-GABA)
Phenibut and gabapentin both modulate GABAergic signalling. Combined use potentiates CNS depression, causing excessive sedation, respiratory depression, and increased addiction risk.
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danger
GHB (Gamma-Hydroxybutyrate) + Phenibut (beta-Phenyl-GABA)
Both phenibut and GHB are potent GABA-B agonists. Combined use causes severe respiratory depression with high risk of coma and death.
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moderate
GABA (Gamma-Aminobutyric Acid) + Phenibut (beta-Phenyl-GABA)
GABA (Gamma-Aminobutyric Acid) and Phenibut (beta-Phenyl-GABA) both push the gaba a and gaba b in the same direction.
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watch
Baclofen (Lioresal) + Phenibut (beta-Phenyl-GABA)
Baclofen (Lioresal) and Phenibut (beta-Phenyl-GABA) both push the gaba b in the same direction.
Serum checks 15 modeled interaction pairings for phenibut (beta-phenyl-gaba) across your whole stack — absorption conflicts, enzyme inhibition, and nutrient depletion included.
Research behind this entry
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Phenibut (beta-phenyl-GABA): a tranquilizer and nootropic drug
Foundational review establishing phenibut as a GABA-mimetic acting primarily at GABA-B and partly at GABA-A receptors, with dopamine-stimulating and PEA-antagonist properties mediating its anxiolytic and nootropic…
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Phenibut (beta-phenyl-gamma-aminobutyric acid) dependence and management of withdrawal: emerging nootropics of abuse
Case report documenting severe phenibut withdrawal (psychomotor agitation, hallucinations, psychosis) requiring ICU admission and baclofen taper, establishing phenibut as an emerging substance of dependence.
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Phenibut: a drug with one too many "buts"
Comprehensive pharmacological review confirming phenibut activity at GABA-B, GABA-A, and beta-PEA receptors, detailing its pharmacokinetics (5.3h half-life, 63% renal excretion unchanged), and documenting escalating…
3 published studies referenced in the app, each with a plain-language summary.