Background: Phenibut is a drug similar in structure to gabapentin and pregabalin. It is available online without prescription, often marketed as a dietary supplement or amino acid derivative. Little is known about phenibut use despite its increased popularity in the United States over the last decade.Objective: To clarify reasons for taking phenibut, circumstances, and effects of use.Methods: Reports of phenibut, gabapentin, and pregabalin use were downloaded from a publicly-available database, Erowid.org. A mixed methods approach utilizing qualitative content analysis was used.Results: Of 229 reports, 211 were from male authors. People usually purchased phenibut online and reportedly used it for recreation, to manage a medical or psychiatric problem (primarily insomnia, anxiety), as a substitute for other drugs (especially benzodiazepines), to manage withdrawal from another substance (including benzodiazepines, opioids), and/or for performance enhancement. While it shared many reported effects with pregabalin and gabapentin such as anxiolysis, increased talkativeness, and impaired motor coordination, reports of gastrointestinal distress and sedation were more commonly attributed to phenibut. Several people reported difficulty in restricting their use and managing withdrawal.Conclusions: Phenibut reports suggest that phenibut may have some benefits for some people. Use also, however, carries risks of adverse effects, a potentially dangerous withdrawal syndrome, and addiction. Not dissimilar to unprescribed gabapentin or pregabalin, self-medication is a common motive for phenibut use. Physicians should continue to ask their patients about use of any non-prescribed medications, dietary supplements, or "amino acid derivatives."Abbreviation: PWUPh: people who use phenibut; PWUG: people who use gabapentin; PWUPr: people who use pregabalin.
Keywords: GABA-B receptor agonists; Substance-related disorders; drug and narcotic control; gamma-aminobutyric acid; qualitative content analysis.