The Detection of Phenibut in Keratinized Specimens: A Validation and Case Study

Phenibut (β-phenyl-γ-butyric acid) is a central nervous system depressant that acts on the GABA_B and to some extent the GABA_A receptors. Phenibut is not approved for human use in the US or throughout most of Europe due to its numerous adverse effects like intoxication, tachycardia, agitation, and confusion. A method to detect phenibut in hair and nail specimens using solid phase extraction followed by liquid chromatography tandem mass spectrometry was validated. This method was used to analyze a pair of hair and fingernail specimens from a self-reported user of phenibut. The assay validation satisfied all the criteria of the ANSI/ASB. Standard Practices for Method Validation in Forensic Toxicology Standard 036. The measured concentration of phenibut in the hair and fingernail of the self-reported phenibut user both greater than the upper limit of linearity (>4000 pg/mg). Phenibut continues to be a growing concern in the United States with limited information on public health outcomes due to scarce availability of testing and interpretation of results. This study is the first report of an analytical method for detection of phenibut in keratinized specimens, including positive detection in both hair and nail of a self-reported user. Keratinized specimens show promise as alternatives for phenibut detection to the more invasive testing matrices, including urine and blood.