Phenibut is a depressant and anxiolytic drug that was first developed in Eastern Europe in the 1960's. Phenibut acts as a full agonist of GABAB receptors, similar to GHB and baclofen. The effects are generally reported to be similar to benzodiazepines.
Phenibut is chemically related to gabapentin and pregabalin, both of which are approved in the West.
Phenibut takes 2-4 hours to begin working, and the effect last for 10 to 16 hours, making it longer-lasting than gabapentin (which lasts only a few hours), clonazepam (6-8 hours), and diazepam (4-6 hours).
Legality and Availability
Phenibut is not FDA approved, and unscheduled by the DEA, meaning that it can be sold as a "supplement" or other non-drug product.
In the UK, phenibut is legal, but cannot be labeled for consumption.
Phenibut is prescribed in Russia, Ukraine, and Latvia for insomnia and anxiety.