Phenibut (IUPAC chemical name: 4-amino-3-phenylbutanoic acid) is a structural analogue of baclofen and gabapentin. It is produced in various formulations, including tablets and powder for oral use and a crystalline form. Phenibut is a registered pharmaceutical in some countries and is also marketed online for a number of uses, including as a sleep aid, mood enhancer, treatment for anxiety and a cognitive enhancer.
Phenibut intoxication can result in central nervous system depressive symptoms, including decreased level of consciousness, muscle tone, stupor, depressed respiration, temperature dysregulation, hyper- or hypotension and coma. Other individuals have presented with agitation, hallucinations, seizures and delirium.
No studies have been conducted in animals on the dependence potential of phenibut. People who use phenibut describe escalating dosing, suggesting tolerance, and difficulty in cessation.
No controlled studies in animals or humans have examined the abuse potential of phenibut. Adverse effects due to nonmedical use of phenibut have been reported from different countries. The doses taken in medically unsupervised use of phenibut obtained on the Internet are often much higher than those used clinically; however, many cases involve multiple drugs and the role of phenibut in these cases remains unclear.
Multiple countries over several regions have reported seizure of phenibut. The extent of non-medical use is unknown.
Phenibut is approved in a few countries as a medicine for various psychiatric and neurological conditions.