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Source inference of exogenous gamma-hydroxybutyric acid (GHB) administered to humans by means of carbon isotopic ratio analysis: novel perspectives regarding forensic investigation and intelligence issues

Marclay, François, Saudan, Christophe, Vienne, Julie, Tafti, Mehdi, Saugy, Martial
Analytical and bioanalytical chemistry 2011 v.400 no.4 pp. 1105-1112
carbon, combustion, forensic sciences, gas chromatography, humans, illicit drugs, isotope fractionation, males, mass spectrometry, metabolism, poisoning, sampling, sedatives, short chain fatty acids, sodium, stable isotopes, statistical analysis, urine, volunteers
γ-Hydroxybutyric acid (GHB) is an endogenous short-chain fatty acid popular as a recreational drug due to sedative and euphoric effects, but also often implicated in drug-facilitated sexual assaults owing to disinhibition and amnesic properties. Whilst discrimination between endogenous and exogenous GHB as required in intoxication cases may be achieved by the determination of the carbon isotope content, such information has not yet been exploited to answer source inference questions of forensic investigation and intelligence interests. However, potential isotopic fractionation effects occurring through the whole metabolism of GHB may be a major concern in this regard. Thus, urine specimens from six healthy male volunteers who ingested prescription GHB sodium salt, marketed as Xyrem®, were analysed by means of gas chromatography/combustion/isotope ratio mass spectrometry to assess this particular topic. A very narrow range of δ¹³C values, spreading from −24.81‰ to −25.06‰, was observed, whilst mean δ¹³C value of Xyrem® corresponded to −24.99‰. Since urine samples and prescription drug could not be distinguished by means of statistical analysis, carbon isotopic effects and subsequent influence on δ¹³C values through GHB metabolism as a whole could be ruled out. Thus, a link between GHB as a raw matrix and found in a biological fluid may be established, bringing relevant information regarding source inference evaluation. Therefore, this study supports a diversified scope of exploitation for stable isotopes characterized in biological matrices from investigations on intoxication cases to drug intelligence programmes.