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Abstract
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Gamma-hydroxybutyric acid (GHB) is an endogenously produced short-chain carboxylic acid naturally present within mammalian species, with trace amounts of GHB produced in various tissues, including the brain, where it functions as both a precursor and a metabolite of the major inhibitory neurotransmitter γ-aminobutyric acid (GABA).1, 2
Administration of sodium salt GHB medications has been common since the 1960s as an anesthetic, and later, it found application in treatment of narcolepsy and cataplexy, alcohol withdrawal syndrome, and alcohol dependence.
Besides its application as a pharmaceutical, illicit use of GHB is also common. GHB, alongside its precursor Gamma-butyrolactone (GBL), which is rapidly transformed in vivo into GHB, is frequently used alone or mixed with other substances such as alcohol as recreational drugs. Small recreational doses of GHB/GBL produce feelings of euphoria with loss of inhibitions, whereas larger doses can induce dizziness, loss of consciousness, and amnesia, and it may lead to strong sedation, coma, and even death. Intentional use of GHB to facilitate the perpetration of crimes is well known, given its disinhibiting properties; the ease with which it can be subtly administered, as it is odorless, colorless, and tasteless, makes it the "perfect date-rape drug" in facilitating a sexual assault (DFSA).
The endogenous-exogenous dual nature of GHB constitutes the main issue for the assessment of its exogenous origin in biological specimens. Several authors underline the importance of a reliable discrimination between basal and exogenous levels in biological samples, which is mandatory to achieve a certain assessment of GHB conscious/unconscious intake.3-5
The detection and identification of exogenous GHB in biological fluids depend on the timeliness of sample collection. In fact, blood and urine samples, in most cases, do not provide conclusive evidence of GHB intake because of the rapid metabolism and elimination of this substance; indeed, the drug can be eliminated from the blood within 6 h and from the urine in less than 12 h.6, 7 Nevertheless, forensic toxicologists are often asked to assess an exogenous administration of GHB, especially in drug-facilitated crimes. As GHB has a very short detection window in conventional biological fluids, usually hair samples are collected and analyzed, the same as for other drugs.
The complexity of distinguishing endogenous GHB levels in the keratin matrix from those caused by exogenous GHB intake is, however, an issue of primary importance in court cases and should be carefully considered, evaluated on a case-by-case basis, and clearly stated to those requesting the analysis (court authorities and DFSA victims).
In fact, for assessment of GHB exogenous origin in hair samples, the evidence of exposure should be present in the segment corresponding to the timeframe of the intake, referred to as "target segment." Rather than the definition of a "per se" cut-off value, it is recommended to consider the concentration ratio between the segment corresponding to the period of intake and the average concentration of the other segments, which represent the subject's basal GHB level. In fact, endogenous GHB concentrations in hair are reported in a wide range by several studies...
Language: en |