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Phenibut (beta-phenyl-GABA, mentioned in the article) is a GABA-B drug discovered in the Soviet Union in the 1960s. It's not approved for any health condition in the US, but is sold as a "dietary supplement". It acts on the same receptor as Baclofen, a prescription drug that's used to relieve muscle spasms and spasticity. In higher doses, it can affect GABA-A, with effects similar to alcohol or some benzodiazepines. After regular use measured in weeks, it can cause a potentially life-threatening withdrawal syndrome that includes seizures.

As someone who's taken it a couple times, didn't get much out of it, and is now amazed he didn't end up in serious trouble: stay the hell away from Phenibut. Or, don't take my word for it: Google for "phenibut withdrawal".