Gamma-hydroxybutyrate (GHB), 1,4-butanediol (1,4BD), and gamma-butyrolactone (GBL) intoxication: A state-of-the-art review

γ-hydroxybutyrate (GHB) is synthesized endogenously from γ-aminobutyric acid (GABA) or exogenously from 1,4-butanediol (butane-1,4-diol; 1,4-BD) or γ-butyrolactone (GBL). GBL, and 1,4-BD are rapidly converted to GHB. The gastric absorption time, volume of distribution, and half-life of GHB are between 5 and 45 min, 0.49 ± 0.9 L/kg, and between 20 and 60 min, respectively. GHB and its analogues have a dose-dependent effect on the activation of GHB receptor, GABA-B, and GABA localized to the central nervous system. After ingestion, most patients present transient neurological disorders (lethal dose: 60 mg/kg). Chronic GHB consumption is associated with disorders of use and a withdrawal syndrome when the consumption is discontinued. GHB, GBL, and 1,4-BD are classified as narcotics but only the use of GHB is controlled internationally. They are used for drug facilitated (sexual) assault, recreational purposes, slamsex, and chemsex. To confirm an exogenous intake or administration of GHB, GBL, or 1-4-BD, the pre-analytical conservation is crucial. The antemortem cutoff doses for detection are 5 and 5-15 mg/L, with detection windows of 6 and 10 h in the blood and urine, respectively Control of GHB is essential to limit the number of users, abuse, associated risks, and death related to their consumption.

Urinary concentrations of GHB and its novel amino acid and carnitine conjugates following controlled GHB administration to humans

Gamma-hydroxybutyrate (GHB) remains a challenging clinical/forensic toxicology drug. Its rapid elimination to endogenous levels mainly causes this. Especially in drug-facilitated sexual assaults, sample collection often occurs later than the detection window for GHB. We aimed to investigate new GHB conjugates with amino acids (AA), fatty acids, and its organic acid metabolites for their suitability as ingestion/application markers in urine following controlled GHB administration to humans. We used LC-MS/MS for validated quantification of human urine samples collected within two randomized, double-blinded, placebo-controlled crossover studies (GHB 50 mg/kg, 79 participants) at approximately 4.5, 8, 11, and 28 h after intake. We found significant differences (placebo vs. GHB) for all but two analytes at 4.5 h. Eleven hours post GHB administration, GHB, GHB-AAs, 3,4-dihydroxybutyric acid, and glycolic acid still showed significantly higher concentrations; at 28 h only GHB-glycine. Three different discrimination strategies were evaluated: (a) GHB-glycine cut-off concentration (1 µg/mL), (b) metabolite ratios of GHB-glycine/GHB (2.5), and (c) elevation threshold between two urine samples (> 5). Sensitivities were 0.1, 0.3, or 0.5, respectively. Only GHB-glycine showed prolonged detection over GHB, mainly when compared to a second time- and subject-matched urine sample (strategy c).

New gamma-hydroxybutyric acid (GHB) biomarkers: Development and validation of a liquid chromatography-tandem mass spectrometry method for the determination of GHB amino acid, carnitine, and fatty acid conjugates in urine

Gamma-hydroxybutyric acid (GHB) represents an important drug in clinical and forensic toxicology, particularly in the context of drug-facilitated crimes. Analytically, GHB remains a major challenge given its endogenous occurrence and short detection window. Previous studies identified a number of potential interesting novel conjugates of GHB with carnitine, amino acids (AA, glutamate, glycine, and taurine), or fatty acids. As a basis for comprehensive studies on the suitability of these novel biomarkers, we developed and validated a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method in human urine. Additionally, already known markers 2,4-dihydroxy butyric acid (2,4-DHB), 3,4-DHB, glycolic acid, succinic acid, succinylcarnitine, and GHB glucuronide were included. The method was fully validated according to (inter)national guidelines. Synthetic urine proved suitable as a surrogate matrix for calibration. Matrix effects were observed for all analytes with suppression effects of about 50% at QC LOW, and approximately 20% to 40% at QC HIGH, but with consistent standard deviation of <25% at QC LOW and <15% at QC HIGH, respectively. All analytes showed acceptable intra- and inter-day imprecision of below 20%, except for inter-day variation of GHB taurine and FA conjugates at the lowest QC. Preliminary applicability studies proved the usefulness of the method and pointed towards GHB glycine, followed by other AA conjugates as the most promising candidates to improve GHB detection. FA conjugates were not detected in urine samples yet. The method can be used now for comprehensive sample analysis on (controlled) GHB administration to prove the usefulness of the novel GHB biomarkers.

Urinary Profile of Endogenous Gamma-Hydroxybutyric Acid and its Biomarker Metabolites in Healthy Korean Females: Determination of Age-Dependent and Intra-Individual Variability and Identification of Metabolites Correlated With Gamma-Hydroxybutyric Acid

Gamma-hydroxybutyric acid (GHB), used as a therapeutic and an illegal anesthetic, is a human neurotransmitter produced during gamma-aminobutyric acid (GABA) biosynthesis and metabolism. Potential biomarker metabolites of GHB intoxication have been identified previously; however, reference concentrations have not been set due to the lack of clinical study data. Urinary profiling of endogenous GHB and its biomarker metabolites in urine samples (n = 472) of 206 healthy females was performed based on differences in age and time of sample collection using liquid chromatography-tandem mass spectrometry following validation studies. The unadjusted and creatinine-adjusted urinary concentrations ranges were obtained after urinary profiling. The creatinine-adjusted concentrations of glutamic and succinic acids and succinylcarnitine significantly increased, whereas that of glycolic acid significantly decreased with advancing age. Significant inter-day variation of GABA concentration and intra-day variation of 3,4-dihydroxybutyric acid and succinylcarnitine concentrations were observed. The urinary concentrations of 2,4-dihydroxybutyric acid, succinic acid, and 3,4-dihydroxybutyric acid showed the highest correlation with that of GHB. Data from this study suggest population reference limits to facilitate clinical and forensic decisions related to GHB intoxication and could be useful for identification of biomarkers following comparison with urinary profiles of GHB-administered populations.

A Retrospective Metabolomics Analysis of Gamma-Hydroxybutyrate in Humans: New Potential Markers and Changes in Metabolism Related to GHB Consumption

GHB is an endogenous short-chain organic acid presumably also widely applied as a rape and knock out drug in cases of drug-facilitated crimes or sexual assaults (DFSA). Due to the endogenous nature of GHB and its fast metabolism in vivo, the detection window of exogenous GHB is however narrow, making it challenging to prove use of GHB in DFSA cases. Alternative markers of GHB intake have recently appeared though none has hitherto been validated for forensic use. UHPLC-HRMS based screening of blood samples for drugs of abuse is routinely performed in several forensic laboratories which leaves an enormous amount of unexploited data. Recently we devised a novel metabolomics approach to use archived data from such routine screenings for elucidating both direct metabolites from exogenous compounds, but potentially also regulation of endogenous metabolism and metabolites. In this paper we used UHPLC-HRMS data acquired over a 6-year period from whole blood analysis of 51 drivers driving under the influence of GHB as well as a matched control group. The data were analyzed using a metabolomics approach applying a range of advanced analytical methods such as OPLS-DA, LASSO, random forest, and Pearson correlation to examine the data in depth and demonstrate the feasibility and potential power of the approach. This was done by initially detecting a range of potential biomarkers of GHB consumption, some that previously have been found in controlled GHB studies, as well as several new potential markers not hitherto known. Furthermore, we investigate the impact of GHB intake on human metabolism. In aggregate, we demonstrate the feasibility to extract meaningful information from archived data here exemplified using GHB cases. Hereby we hope to pave the way for more general use of the principle to elucidate human metabolites of e.g. new legal or illegal drugs as well as for applications in more global and large scale metabolomics studies in the future.

Quantification of succinic acid levels, linked to succinate dehydrogenase (SDH) dysfunctions, by an automated and fully validated liquid chromatography tandem mass spectrometry method suitable for multi-matrix applications

The hallmarks of cancer include metabolism with deregulating cellular energetics. Dysfunctions in succinate dehydrogenase (SDH) metabolic enzyme activity, leading to an abnormal accumulation of succinic acid has been described in solid tumors but also in inflammation and ischemia reperfusion injury. Succinic acid is a potential biomarker of SDH related pathologies for diagnostic, evaluation of treatment response and follow-up of the disease. We developed a liquid chromatography tandem mass spectrometry (LC-MS/MS) method allowing a rapid, accurate and precise quantification of succinic acid levels in clinical (serum, urine) and preclinical (cellular pellets, supernatants) samples. ¹³C₄ succinic acid disodium salt was used as internal standard and added to samples before a solid phase extraction (SPE) on Phenomenex STRATA^TM XL-A (200 mg - 3 mL) 33 µm cartridges. This method is automated by a Freedom EVO® platform from TECAN and succinic acid is separated on a C18 column combined to a Xevo® TQ-S micro Waters mass spectrometer with electrospray ionization (ESI) source. This biomedical analysis allows standard curves to be linear over the range 1.0-135.5 µM with r² values > 0.999 and low matrix effects (<9.1 %). This method, which is validated according updated European Medicine Agency (EMA) guidelines, is accurate between-run (<11.0 %) and within-run (<7.8 %), precise between-run (<14.4 CV %) and within-run (<3.7 CV %), and is suitable for clinical and preclinical applications.

Fatty acid esters as novel metabolites of γ-hydroxybutyric acid: A preliminary investigation

γ-Hydroxybutyric acid (GHB) is a substance frequently abused as a knockout agent. Because of possible amnesia experienced by victims of GHB exposure and the short detection time of GHB in biological samples, the proof of GHB uptake is often challenging for forensic toxicologists. For this reason, various approaches have been evaluated to prolong the detection of GHB intake. In the present study, a fatty acid ester of GHB (4-palmitoyloxy butyrate [GHB-Pal; 3-carboxypropyl hexadecanoate]) was synthesized with the intent of examining whether such esters could be detected as metabolites of GHB in blood samples. Using the structurally elucidated synthesis product (structural elucidation by means of high performance liquid chromatography quadrupole time of flight mass spectrometry [LC-QToF-MS]), an LC triple quadrupole mass spectrometric (LC-MS/MS) method was established for the detection of GHB-Pal. Blood (plasma) samples from four cases in which GHB was previously detected at relevant concentrations (56.1-96.5 μg/ml) were analyzed with respect to GHB-Pal. Signals for GHB-Pal, as well as possible signals for other fatty acid esters of GHB, were detectable in these specimens. (Negative) control samples (20 plasma samples and 20 red blood cell/blood clot samples; from cases in which an intake of GHB or its precursors was not assumed) were all negative for GHB-Pal. To evaluate a possible forensic benefit of GHB fatty acid esters (prolongation of the detection window of a GHB uptake), the analysis of additional plasma samples collected after GHB uptake (or controlled GHB administration) and quantification of GHB fatty acid esters are needed.

GHB related acids are useful in routine casework of suspected GHB intoxication cases

GHB related acids (3,4-dihydroxy butyric acid, 2,4-dihydroxy butyric acid and glycolic acid) are produced through oxidative GHB metabolism. These analytes could be potential biomarkers to ensure the diagnosis of a GHB intoxication and even prolong the detection window. Within this study, forensic routine cases were measured to consider the potential of additional gas chromatographic mass spectrometric analysis on these acids. 17 GHB positive real cases (10 serum samples and 7 urine samples) and 40 cases with suspicion of drugging in DFC cases and negative GHB results (21 serum samples and 19 urine samples) were evaluated. Increased GHB related acid concentrations were detected in all serum and most urine samples positive on GHB. In some GHB negative cases, especially in serum samples, concentrations of GHB related acids gave hints that GHB actually was taken. We recommend to use the following cut-offs for a more reliable interpretation of potential GHB intoxication cases: 3,4-OH-BA:>3 mg/L in serum and>50 mg/L in urine; 2,4-OH-BA:>2 mg/L in serum and>25 mg/L in urine; GA:>5 mg/L in serum and>400 mg/L in urine.

Detection of γ-hydroxybutyric acid-related acids in blood plasma and urine: Extending the detection window of an exogenous γ-hydroxybutyric acid intake?

In crimes facilitated by γ-hydroxybutyric acid (GHB) administration, the frequent occurrence of anterograde amnesia of the victims as well as the short detection window and variations of endogenous GHB concentrations complicate obtaining analytical proof of GHB administration. Because elevated endogenous organic acid concentrations have been found in the urine of patients with succinic semialdehyde deficiency (leading to accumulation of GHB in human specimens) and after GHB ingestion, we searched for an alternative way to prove GHB administration via detection of elevated organic acid concentrations in blood plasma and urine. We collected blood and urine samples from narcolepsy patients (n = 5) treated with pharmaceuticals containing GHB sodium salt (1.86-3.72 g GHB as free acid per dose). Although GHB was detectable only up to 4 h in concentrations greater than the commonly used cutoff levels in blood plasma, 3,4-dihydroxybutyric acid (3,4-DHB) could be detected up to 12 h in blood plasma in concentrations exceeding initial concentrations of the same patient before GHB ingestion. Furthermore, four of the five patients showed an increase above endogenous levels described in the scientific literature. In urine, GHB concentrations above commonly used cutoff levels could be observed 4.5-9.5 h after GHB intake. Creatinine standardized initial concentrations were reached again for glycolic acid (GA), 3,4-DHB, and 2,4-dihydroxybutyric (2,4-DHB) acid at 6.5-22, 11.5-22, and 8.5-70 h after GHB intake, respectively. Therefore, 2,4-DHB, 3,4-DHB, and GA are promising and should be further investigated as potential biomarkers to prolong the detection window of GHB intake.

Towards Extending the Detection Window of Gamma-Hydroxybutyric Acid-An Untargeted Metabolomics Study in Serum and Urine Following Controlled Administration in Healthy Men

In forensic toxicology, gamma-hydroxybutyrate (GHB) still represents one of the most challenging drugs of abuse in terms of analytical detection and interpretation. Given its rapid elimination, the detection window of GHB in common matrices is short (maximum 12 h in urine). Additionally, the differentiation from naturally occurring endogenous GHB, is challenging. Thus, novel biomarkers to extend the detection window of GHB are urgently needed. The present study aimed at searching new potential biomarkers of GHB use by means of mass spectrometry (MS) metabolomic profiling in serum (up to 16.5 h) and urine samples (up to 8 h after intake) collected during a placebo-controlled crossover study in healthy men. MS data acquired by different analytical methods (reversed phase and hydrophilic interaction liquid chromatography; positive and negative electrospray ionization each) were filtered for significantly changed features applying univariate and mixed-effect model statistics. Complementary to a former study, conjugates of GHB with glycine, glutamate, taurine, carnitine and pentose (ribose) were identified in urine, with particularly GHB-pentose being promising for longer detection. None of the conjugates were detectable in serum. Therein, mainly energy metabolic substrates were identified, which may be useful for more detailed interpretation of underlying pathways but are too unspecific as biomarkers.