Phenibut

Phenibut has anxiolytic and nootropic (cognition enhancing) effects. It acts as a GABA-mimetic, primarily at GABAB and, to some extent, at GABAA receptors. It also stimulates dopamine receptors and antagonizes β-phenethylamine (PEA), a putative endogenous anxiogenic^[1].

At doses that do not affect motor activity (e.g., 20 mg/kg i.p.), Phenibut inhibits food conditioned reflexes in mice. At doses higher than 70 mg/kg i.p., Phenibut reduces motor and exploratory activities, rearings, muscle tone, coordination and body temperature. Following intravenous administration to either rabbits or rats phenibut is not metabolized. Phenibut is largely excreted in the urine. At 15, 30, 60, or 90 min following i.v. administration Phenibut is found in liver, kidneys, and urine. Traces of phenibut are found in blood and brain. 180 min after i.v. injection only traces of the drug are found in all tissues studied. In cats and dogs, phenibut, after a single dose of 50 mg/kg i.v., is excreted in the urine unchanged. The acute toxicity of phenibut is low. Its LD50 is 900 mg/kg i.p. in mice and 700 mg/kg i.p. in rats^[1]. Phenibut administration leads to decreases in horizontal movement activity and some elements of investigative behavior in rabbits in the open field, along with decreases in the reactivity of the animals to emotionally significant stimuli^[2].