However, Phenibut FAA can be a absolutely free amino acid type, which is not as soluble but is believed to have higher bioavailability.GABA-B Receptor Agonist: The key mechanism of action of phenibut is being an agonist with the GABA-B (gamma-aminobutyric acid kind B) receptors. GABA is the first inhibitory neurotransmitter inside the Mind, and its