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GABA-B Agonist

Phenibut

Overview

An anxiolytic/sleep aid prescribed in some countries; widely associated with tolerance, dependence, and a dangerous withdrawal syndrome, and with overdose risk when combined with other depressants.

How it works

Phenibut is a derivative of the calming neurotransmitter GABA, modified (with a phenyl group) so it can cross into the brain. It's used as an anti-anxiety and sleep aid in some countries.

Its main action is as a GABA-B receptor agonist — similar in spirit to the muscle relaxant baclofen — and one of its forms also acts on calcium channels in a gabapentin-like way, with weak GABA-A activity at higher doses. The net result is enhanced inhibitory (calming) signaling in the brain.

The serious caveat is its abuse and dependence potential: tolerance builds quickly, abrupt withdrawal can be severe (including agitation, psychosis, and seizures), and combining it with alcohol or other depressants is dangerous. It is not FDA-approved and is regulated or banned in several places.

Mechanism · Detailed Analysis
Molecular targetPrimarily a GABA-B receptor agonist (baclofen-like); the R-enantiomer also binds the α2δ subunit of voltage-gated calcium channels (gabapentinoid activity), with weak GABA-A effects at higher doses.
Signaling & downstream effectsNet enhancement of inhibitory neurotransmission produces anxiolysis and sedation; the phenyl group lets it cross the blood-brain barrier.
PharmacokineticsLong-acting relative to GABA itself.
CaveatsRapid tolerance and dependence; abrupt withdrawal can be severe (agitation, psychosis, seizures), and combining with other CNS depressants is dangerous.
Published EvidenceLoading cited studies from PubMed…
Human Data ···

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Animal ···

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Educational aggregation of public literature. Not medical advice and not a recommendation to use any compound. Many compounds here are not approved for human use. Consult a licensed clinician.