Phenibut is an anti-anxiety drug with cognitive enhancing properties, which boosts memory recall and exam performance. Originally given to Soviet cosmonauts to combat anxiety and insomnia, the powdered drug is suspected to have played a role in the recent overdose of seven teenagers at a Queensland private school.

Phenibut is similar in structure to a type of neurotransmitter known as neurotransmitter γ-aminobutyric acid (GABA), which plays a role in reducing excitability and anxiety, as well as enhancing euphoria and cognitive function. Phenibut binds to a specific subtype of the GABA receptor, activating a similar reaction as GABA.

Animal studies have shown that phenibut is able to penetrate the blood-brain barrier. Once phenibut reaches the brain the result is reduced anxiety and social inhibition. Because it depresses the central nervous system (like GABA), it is also used as a mood elevator and tranquilizer.

Phenibut can be used to treat anxiety, post-traumatic stress disorder, alcohol withdrawal syndrome and vestibular (balance) disorders such as vertigo. Phenibut is not licensed for use in the European Union, Australia or the United States due to safety concerns, since it "represents a significant risk of harm, including overdose".

Phenibut is commercially available in the daily doses ranges from 500 to 2000 mg. It was available as a powder in amounts ranging from 5 g to 1,000 kg and as capsules containing 200–500 mg in packs of between six and 360.

Side effects of phenibut are generally linked to its central nervous system depressant effects, such as sedation and problems with breathing. There is currently limited information about phenibut. But because it has similar pharmacological properties to baclofen it's likely to have similar side effects.

These include gastrointestinal symptoms (nausea, vomiting, diarrhea), central nervous system symptoms (insomnia, confusion, euphoria, depression, hallucinations), and visual disturbances and musculoskeletal symptoms (such as tremors).

Users of phenibut can also develop tolerance within days, needing more of the drug to feel the same effects. This can increase the risk of adverse effects. Users may develop withdrawal effects, such as severe rebound anxiety and insomnia, when they stop taking the drug.

Despite phenibut not being registered or legally available in Australia, the Therapeutic Goods Administration has received three reports of problems related to phenibut use in the past five years. These cases range from isolated symptoms of headaches, to a cluster of symptoms such as visual impairment, muscle spasms, palpitations and nausea/vomiting.

The reported adverse events of phenibut are just scratching the surface of a largely unregulated online drug market with no standards of quality assurance. So for those students seeking the competitive edge, it looks like those extra marks are not worth it after all.