Purchasing "Nootropics" Online: Identification and Quantification of Ingredients in Phenibut-Containing Products.

: Phenibut is a central nervous system drug that is registered and used in clinical practice as a prescription medication. In recent decades, the drug has become popular as a "nootropic and cognition enhancer" because of its active marketing as a dietary or food supplement sold online. This has resulted in a growing number of case reports on acute toxicity and withdrawal symptoms and has raised concerns about the quality of phenibut-containing products. : We used high-performance liquid chromatography with diode-array detection and ultra-performance liquid chromatography-mass spectrometry to investigate the quality of six phenibut-containing samples purchased from three internet suppliers. : Substantially lower levels of the active pharmaceutical ingredient than claimed on the packaging were found for three of the supplements tested. A considerably higher level of phenibut was present in one product. All online-purchased phenibut-containing capsules included declared and undeclared ingredients found in various dietary supplements claiming to have metabolic, neurotropic, antioxidant, anti-inflammatory, and neuroprotective properties. : The online-purchased phenibut products contained undeclared ingredients and the content of phenibut differed from the declared. The combinations of these additional ingredients with phenibut have not been tested for activity or safety and their use warrants further attention to avoid potential health problems.