An overview of gamma-hydroxybutyric acid: pharmacodynamics, pharmacokinetics, toxic effects, addiction, analytical methods, and interpretation of results

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.

Smartphone-based colorimetric determination of gamma-butyrolactone and gamma-hydroxybutyrate in alcoholic beverage samples

Gamma-hydroxybutyrate (GBH) is a popular recreational drug. Its strong sedative and amnesic effects have led to drug-facilitated sexual assaults, poisonings, overdose, and death. As a result, legislation has restricted its availability leading to GHB, consumers switching to its pro-drug, gamma-butyrolactone (GBL). Consequently, there is a growing need for methods capable of their determination in complex samples such as beverages. Previous studies have shown the possibility to colorimetrically qualitatively determine both GBH and GBL by the formation of the lactone and its reaction with hydroxylamine and ferric chloride to give a purple-colored complex. In this present investigation, we have shown the possibility of using this approach to both quantify GBL and GHB using both UV/Vis spectrometry and by the application of the camera of a smartphone to record images of the purple color developed. Via subsequent use of a downloadable free App, to extract the numerical values of the Red, Green, and Blue (RGB) color components, it was shown possible to construct a calibration curve and to quantitatively determine the concentration of the drugs present in fortified alcoholic beverage samples. It was found that by simple mathematical normalization of the RGB values the effects of camera distance and elimination could be readily overcome. Using the smartphone approach, GBL determinations on a sample of lager beer gave a mean recovery of 103% (%CV = 0.70%, n = 5) at a concentration of 0.56 mg/ml indicating the method holds promise for the determination of GBL and GHB in such samples.

Learning and memory impairment induced by 1,4-butanediol is regulated by ERK1/2-CREB-BDNF signaling pathways in PC12 cells

1,4-butanediol (1,4-BD) is a known γ-hydroxybutyric acid (GHB) precursor which affects the nervous system after ingestion, leading to uncontrolled behavioral consequences. In the present study, we investigated whether 1,4-BD induces oxidative stress and inflammation in PC12 cells and evaluated the toxic effects of 1,4-BD associates with learning and memory. CCK-8 results revealed a dose-effect relationship between the cell viability of PC12 cells and 1,4-BD when the duration of action was 2 h or 4 h. Assay kits results showed that 1,4-BD decreased the levels of Glutathione (GSH), Glutathione peroxidase (GSH-px), Superoxide dismutase (SOD), Acetylcholine (Ach) and increased the levels of Malondialdehyde (MDA), Nitric oxide (NO) and Acetylcholinesterase (AchE). Elisa kits results indicated that 1,4-BD decreased the levels of synaptophysin I (SYN-1), Postsynaptic density protein-95 (PSD-95), Growth associated protein-43 (GAP-43) and increased the levels of Tumor necrosis factor alpha (TNF-α) and Interleukin- 6 (IL-6). RT-PCR results showed that the mRNA levels of PSD-95, SYN-1 and GAP-43 were significantly decreased. The expression of phosphorylation extracellular signal-regulated protein kinase 1/2 (p-ERK1/2), phosphorylation cAMP response element binding protein (p-CREB) and brain-derived neurotrophic factor (BDNF) proteins were significantly decreased in PC12 cells by protein blotting. Overall, these results suggest that 1,4-BD may affect synaptic plasticity via the ERK1/2-CREB-BDNF pathway, leading to Ach release reduction and ultimately to learning and memory impairment. Furthermore, oxidative stress and inflammation induced by 1,4-BD may also result in learning and memory deficits. These findings will enrich the toxicity data of 1.4-BD associated with learning and memory impairment.

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.

The Identification of Gamma-Butyrolactone in JUUL Liquids

Gamma-Butyrolactone (GBL), a commonly used industrial solvent, is used recreationally as a central nervous system (CNS) depressant and, therefore, a United States Drug Enforcement Agency (DEA) List 1 chemical of the Controlled Substances Act. GBL was identified presumptively in the liquid from JUUL Virginia Tobacco flavored pods during routine untargeted screening analysis of e-cigarette products by gas chromatography-mass spectrometry (GC-MS). Methods for the confirmation and quantitation of GBL were developed for GC-MS and liquid chromatography-tandem mass spectrometry (LC-MS-MS) in the liquids and the aerosol generated from the liquid. Three flavors of JUUL pods available at the time of analysis were obtained by direct purchase from the manufacturer, purchase from a local vape shop, and via submission from a 3rd party. The only liquid flavor to contain GBL was Virginia Tobacco, with an average of 0.37 mg/mL of GBL, and it was detected in the aerosol. Studies evaluating the pharmacological effects of inhaling GBL do not exist, however a case report of chronic oral GBL ingestion indicates acute lung injury. The identification of GBL in an e-cigarette product purportedly compliant with federal regulation continues to demonstrate public health and public safety concerns.

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.

Metabolic Alterations Associated with γ-Hydroxybutyric Acid and the Potential of Metabolites as Biomarkers of Its Exposure

γ-Hydroxybutyric acid (GHB) is an endogenous short chain fatty acid that acts as a neurotransmitter and neuromodulator in the mammalian brain. It has often been illegally abused or misused due to its strong anesthetic effect, particularly in drug-facilitated crimes worldwide. However, proving its ingestion is not straightforward because of the difficulty in distinguishing between endogenous and exogenous GHB, as well as its rapid metabolism. Metabolomics and metabolism studies have recently been used to identify potential biomarkers of GHB exposure. This mini-review provides an overview of GHB-associated metabolic alterations and explores the potential of metabolites for application as biomarkers of GHB exposure. For this, we discuss the biosynthesis and metabolism of GHB, analytical issues of GHB in biological samples, alterations in metabolic pathways, and changes in the levels of GHB conjugates in biological samples from animal and human studies. Metabolic alterations in organic acids, amino acids, and polyamines in urine enable discrimination between GHB-ingested animals or humans and controls. The potential of GHB conjugates has been investigated in a variety of clinical settings. Despite the recent growth in the application of metabolomics and metabolism studies associated with GHB exposure, it remains challenging to distinguish between endogenous and exogenous GHB. This review highlights the significance of further metabolomics and metabolism studies for the discovery of practical peripheral biomarkers of GHB exposure.

Gamma-Hydroxybutyrate (GHB) Withdrawal in a Patient with Polysubstance Use

Gamma-hydroxybutyrate (GHB) and its various pro-drugs are GABA-B central nervous system depressants more commonly known as "G" and "liquid ecstasy" among those who consume. Due to the depressant quality of the substance and its convenience in online marketplaces, it has become a more commonly abused drug, characteristically among people involved in the "club scene" and among men who have sex with men. As the dose of GHB necessary to obtain feelings of euphoria is relatively low combined with the substance's rapid metabolism, GHB is nearly undetectable through traditional emergency department urinary drug testing. Consequentially, although the treatment of GHB intoxication and withdrawal is mainly supportive, it is difficult for providers to determine whether GHB is the cause of a patient's symptoms. Moreover, when GHB is combined with other substances, treatment becomes more complicated. The author presents a case of GHB intoxication and withdrawal in a patient with an extensive polysubstance use history demonstrating not only the difficulty of diagnosis but also a timeline outlining the interventions taken from arrival to discharge with a successful outcome faster than the conventional timeline of GHB withdrawal and recovery.

Evidence of Natural GHB Presence in Energy Drinks: Caution in Data Interpretation in Suspected DFSA Cases

Gamma-hydroxybutyric acid (GHB), usually reported as rape drug in drug-facilitated sexual assaults (DFSA), is an endogenous substance in human body and is also found in many beverages. This may lead to data misinterpretation in forensic cases. Herein, we aimed to collect evidence about natural GHB presence in 13 energy drinks (ED). After a liquid–liquid extraction with acidic ethyl acetate, samples were derivatized with BSTFA 1% TMCS. Analyses were carried out by a GC–MS system in SIM mode (GHB, 233, 234, 143 and 147 m/z; GHB-d6, 239, 240, 120 and 206 m/z). GHB was present in all the samples at very low concentrations ranging from 98 to 197 ng/mL. Thus, GHB presence in ED is not exclusively related to exogenous addition. Since the GHB levels are far lower than the minimum active dose (i.e., 0.5 g), it is not expected to induce any effect.

Organocatalytic Asymmetric Conjugate Addition of Aldehydes to Maleimides and Nitroalkenes in Deep Eutectic Solvents

A chiral primary amine-salicylamide is used as an organocatalyst for the enantioselective conjugate addition of α,α-disubstituted aldehydes to maleimides and nitroalkenes. The reactions are performed in deep eutectic solvents as reaction media at room temperature, leading to the corresponding adducts with enantioselectivities up to 88% (for maleimides) and 80% (for nitroalkenes). Catalyst and solvent can be recovered and reused.

Prospective Investigation of the Performance of 2 Gamma-Hydroxybutyric Acid Tests: DrugCheck GHB Single Test and Viva-E GHB Immunoassay

BACKGROUND

Gamma-hydroxybutyric acid (GHB) is a recreational drug with central nervous system depressing effects that is often abused. A urine GHB point-of-care test can be of great diagnostic value. The objective of this prospective study was to determine the performance of the new DrugCheck GHB Single Test and the Viva-E GHB immunoassay for urine samples in emergency department patients.

METHODS

Patients presented to the emergency department of the OLVG hospital in Amsterdam with a Glasgow Coma Scale score <15 and potential drug of abuse intoxication were included in the study. Between June 2016 and October 2017, 375 patients were included. Using the DrugCheck GHB Single Test (Express Diagnostics Int'l, Blue Earth, MN) and the Viva-E GHB immunoassay (Siemens Healthineers, The Hague, the Netherlands), patients' urine samples were tested for GHB (cutoff for a positive result, 10 or 50 mcg/mL GHB). To ensure quality, the results obtained were compared with those generated using a validated gas chromatography method. The tests were considered reliable if specificity and sensitivity were both >90%. Possible cross-reactivity with ethanol was investigated by analyzing ethanol concentrations in patients' samples.

RESULTS

Seventy percentage of the included patients was men, and the median age was 34 years old. The DrugCheck GHB Single Test's specificity and sensitivity were 90.0% and 72.9%, respectively, and using 50 mcg/mL as a cutoff value, its specificity and sensitivity improved to 96.7% and 75.0%, respectively. Serum and urine ethanol levels in the false-positive group were significantly higher compared with those in the true-negative group. The specificity and sensitivity of the Viva-E GHB immunoassay (cutoff value of 50 mcg/mL and excluding samples with ethanol levels ≥2.0 g/L) were 99.4% and 93.5%, respectively.

CONCLUSIONS

The DrugCheck GHB Single Test's specificity was sufficient, whereas its sensitivity was poor, making it unsuitable for use at point-of-care. Contrarily, using 50 mcg/mL as the cutoff value and excluding samples with ethanol levels ≥2.0 g/L, the Viva-E GHB immunoassay showed acceptable results to detect clinically relevant GHB intoxications.

Effects of gamma-hydroxybutyrate on neurophysiological correlates of performance and conflict monitoring

Performance and conflict monitoring (PM and CM) represent two essential cognitive abilities, required to respond appropriately to demanding tasks. PM and CM can be investigated using event-related brain potentials (ERP) and associated neural oscillations. Namely, the error-related negativity (ERN) represents a correlate of PM, whereas the N2 component reflects the process of CM. Both ERPs originate in the anterior cingulate cortex (ACC) and PM specifically has been shown to be susceptible to gamma-aminobutyric acid (GABA) A receptor activation. Contrarily, the specific effects of GABA_B receptor (GABA_BR) stimulation on PM and CM are unknown. Thus, the effects of gamma-hydroxybutyrate (GHB; 20 and 35 mg/kg), a predominant GABA_BR agonist, on behavioral and electrophysiological correlates of PM and CM were here assessed in 15 healthy male volunteers, using the Eriksen-Flanker paradigm in a randomized, double-blind, placebo-controlled, cross-over study. Electroencephalographic (EEG) data were analyzed in the time and time-frequency domains. GHB prolonged reaction times, without affecting error rates or post-error slowing. Moreover, GHB decreased ERN amplitudes and associated neural oscillations in the theta/alpha1 range. Similarly, neural oscillations associated with the N2 were reduced in the theta/alpha1 range, while N2 amplitude was conversely increased. Hence, GHB shows a dissociating effect on electrophysiological correlates of PM and CM. Reduced ERN likely derives from a GABA_BR-mediated increase in dopaminergic signaling, disrupting the generation of prediction errors, whereas an enhanced N2 suggests an increased susceptibility towards external stimuli. Conclusively, GHB is the first drug reported, thus far, to have opposite effects on PM and CM, underlined by its unique electrophysiological signature.

Modulation of Social Cognition via Hallucinogens and "Entactogens"

Social cognition is a fundamental ability in human everyday lives. Deficits in social functioning also represent a core aspect of many psychiatric disorders. Yet, despite its significance, deficits in social cognition skills are insufficiently targeted by current treatments. Hallucinogens and entactogens have been shown to have the potential to modulate social processing. This article reviews the literature on the influence of hallucinogens and entactogens on social processing in controlled experimental studies in humans and elucidates the underlying neurobiological and neuropharmacological mechanisms. Furthermore, it identifies current knowledge gaps and derives implications for hallucinogen-assisted treatment approaches as well as the development of novel medication for trans-diagnostic impairments in social cognition.

Prohedonic properties of gamma-hydroxybutyrate are associated with changes in limbic resting-state functional connectivity

OBJECTIVE

Gamma-hydroxybutyrate (GHB) is an endogenous GHB-/GABA-B receptor agonist and a narcolepsy treatment. However, GHB is also abused for its prohedonic effects. On a neuronal level, it was shown that GHB increases regional cerebral blood flow in limbic areas such as the right anterior insula (rAI) and the anterior cingulate cortex (ACC). We aimed to further explore the association between the subjective and neuronal signatures of GHB.

METHOD

We assessed subjective effects and resting-state functional connectivity (rsFC) of an rAI- and an ACC-seed in 19 healthy male subjects after GHB (35 mg/kg p.o.) using a placebo-controlled, double-blind, randomized, cross-over functional magnet resonance imaging design.

RESULTS

GHB increased subjective ratings for euphoria (p < 0.001) and sexual arousal (p < 0.01). Moreover, GHB increased rAI-rsFC to the right thalamus and the superior frontal gyrus and decreased ACC-rsFC to the bilateral paracentral lobule (all p < 0.05, cluster corrected). Moreover, GHB-induced euphoria was associated with rAI-rsFC to the superior frontal gyrus (p < 0.05, uncorrected).

CONCLUSIONS

GHB induces prohedonic effects such as euphoria and sexual arousal and in parallel modulates limbic rsFC with areas linked to regulation of mood, cognitive control, and sexual experience. These results further elucidate the drug's effects in neuropsychiatric disorders and as drug of abuse.

Asymmetric Conjugate Addition of α,α-Disubstituted Aldehydes to Nitroalkenes Organocatalyzed by Chiral Monosalicylamides from trans-Cyclohexane-1,2-Diamines

Primary amine-salicylamides derived from chiral trans-cyclohexane-1,2-diamines are used as organocatalysts for the enantioselective conjugate addition of α,α-disubstituted aldehydes to arylated and heteroarylated nitroalkenes. The reaction is performed in the presence of 4-dimethylaminopyridine as an additive in dichloromethane as a solvent at room temperature. The corresponding enantioenriched γ-nitroaldehydes are obtained with enantioselectivities up to 95%. Theoretical calculations are used to justify the reasons of the stereoinduction.

[Cause of Death: 'Intoxication' - a Matter of the Concentration?]

Cause of Death: 'Intoxication' - a Matter of the Concentration? Abstract. Elucidation of the cause of death is one of the main reasons for medico-legal investigations. In clinical toxicology, the severity of a given poisoning is typically assessed with the blood concentration of a pharmacologically or toxicologically active compound. Such an interpretation proves to be difficult or even impossible in postmortem toxicology. Numerous biochemical and biological processes beginning immediately after death may render the calculated drug concentration unreliable. Concentrations obtained from postmortem samples do not necessarily reflect the blood concentration at the time of death. A prediction if and to what extent such postmortem changes might have occurred is still impossible for individual cases. Interpretation therefore needs to be done with care, considering case circumstances and all available information.

Gamma-Hydroxybutyrate Increases Resting-State Limbic Perfusion and Body and Emotion Awareness in Humans

Gamma-hydroxybutyrate (GHB) is a GHB-/GABA-B receptor agonist inducing a broad spectrum of subjective effects including euphoria, disinhibition, and enhanced vitality. It is used as treatment for neuropsychiatric disorders including narcolepsy and alcohol withdrawal, but is also a drug of abuse. Non-medical users report enhancement of body and emotion awareness during intoxication. However, the neuronal underpinnings of such awareness alterations under GHB are unknown so far. The assessment of regional cerebral blood flow (rCBF) by pharmacological magnetic resonance imaging (phMRI) enables the elucidation of drug-induced functional brain alterations. Thus, we assessed the effects of GHB (35 mg/kg p.o.) in 17 healthy males on rCBF and subjective drug effects, using a placebo-controlled, double-blind, randomized, cross-over design employing arterial spin labeling phMRI. Compared to placebo, GHB increased subjective ratings for body and emotion awareness, and for dizziness (p<0.01-0.001, Bonferroni-corrected). A whole-brain analysis showed increased rCBF in the bilateral anterior cingulate cortex (ACC) and the right anterior insula under GHB (p<0.05, cluster-corrected). ACC and insula rCBF are correlated with relaxation, and body and emotion awareness (p<0.05-0.001, uncorrected). Interaction analyses revealed that GHB-induced increase of body awareness was accompanied by increased rCBF in ACC, whereas relaxation under GHB was accompanied by elevated rCBF in right anterior insula (p<0.05, uncorrected). In conclusion, enhancement of emotion and body awareness, and increased perfusion of insula and ACC bears implications both for the properties of GHB as a drug of abuse as well as for its putative personalized potential for specific therapeutic indications in affective disorders.

Neural underpinnings of prosexual effects induced by gamma-hydroxybutyrate in healthy male humans

Gamma-hydroxybutyrate (GHB) is a GHB-/GABA_B-receptor agonist currently used as treatment for narcolepsy but also as a drug of abuse. Non-medical GHB users have repeatedly reported prosexual effects including libido-enhancement and lowering of attractiveness standards for partner selection. Here, we examined the putative prosexual effects of oral GHB in healthy males in two experiments both employing randomized, placebo-controlled, double-blind, balanced, and cross-over study designs. In experiment I, subjective effects of 20 and 35mg/kg GHB vs. placebo were tested in 32 participants using the Sexual Arousal and Desire Inventory. In experiment II, brain reactivity towards erotic vs. neutral pictures was investigated in 15 participants using functional magnetic resonance imaging after 35mg/kg GHB vs. placebo. In experiment I, prosexual effects of GHB were shown by increased SADI ratings regarding physiological, evaluative, and motivational aspects of sexual arousal. In experiment II, erotic visual stimuli activated the bilateral insula, nucleus accumbens (NAcc), fusiform gyrus, thalamus, and left occipital pole under placebo. After GHB administration, even sexually neutral pictures of persons induced subjective sexual arousal and increased activation of the bilateral NAcc and right anterior cingulate cortex, which significantly correlated (left NAcc by trend). Moreover, a psychophysiological interaction analysis showed that GHB increased connectivity between NAcc and ventromedial prefrontal cortex during processing of visual erotic cues, i.e., in the condition in which subjective sexual arousal was highest. Our data show that GHB stimulates hedonic sexual functioning and lowers the threshold for erotic perception, which is related to increased susceptibility of mesolimbic reward pathways.

Catabolism of GABA, succinic semialdehyde or gamma-hydroxybutyrate through the GABA shunt impair mitochondrial substrate-level phosphorylation

GABA is catabolized in the mitochondrial matrix through the GABA shunt, encompassing transamination to succinic semialdehyde followed by oxidation to succinate by the concerted actions of GABA transaminase (GABA-T) and succinic semialdehyde dehydrogenase (SSADH), respectively. Gamma-hydroxybutyrate (GHB) is a neurotransmitter and a psychoactive drug that could enter the citric acid cycle through transhydrogenation with α-ketoglutarate to succinic semialdehyde and d-hydroxyglutarate, a reaction catalyzed by hydroxyacid-oxoacid transhydrogenase (HOT). Here, we tested the hypothesis that the elevation in matrix succinate concentration caused by exogenous addition of GABA, succinic semialdehyde or GHB shifts the equilibrium of the reversible reaction catalyzed by succinate-CoA ligase towards ATP (or GTP) hydrolysis, effectively negating substrate-level phosphorylation (SLP). Mitochondrial SLP was addressed by interrogating the directionality of the adenine nucleotide translocase during anoxia in isolated mouse brain and liver mitochondria. GABA eliminated SLP, and this was rescued by the GABA-T inhibitors vigabatrin and aminooxyacetic acid. Succinic semialdehyde was an extremely efficient substrate energizing mitochondria during normoxia but mimicked GABA in abolishing SLP in anoxia, in a manner refractory to vigabatrin and aminooxyacetic acid. GHB could moderately energize liver but not brain mitochondria consistent with the scarcity of HOT expression in the latter. In line with these results, GHB abolished SLP in liver but not brain mitochondria during anoxia and this was unaffected by either vigabatrin or aminooxyacetic acid. It is concluded that when mitochondria catabolize GABA or succinic semialdehyde or GHB through the GABA shunt, their ability to perform SLP is impaired.

Novel Psychoactive Substances-Recent Progress on Neuropharmacological Mechanisms of Action for Selected Drugs

A feature of human culture is that we can learn to consume chemical compounds, derived from natural plants or synthetic fabrication, for their psychoactive effects. These drugs change the mental state and/or the behavioral performance of an individual and can be instrumentalized for various purposes. After the emergence of a novel psychoactive substance (NPS) and a period of experimental consumption, personal and medical benefits and harm potential of the NPS can be estimated on evidence base. This may lead to a legal classification of the NPS, which may range from limited medical use, controlled availability up to a complete ban of the drug form publically accepted use. With these measures, however, a drug does not disappear, but frequently continues to be used, which eventually allows an even better estimate of the drug's properties. Thus, only in rare cases, there is a final verdict that is no more questioned. Instead, the view on a drug can change from tolerable to harmful but may also involve the new establishment of a desired medical application to a previously harmful drug. Here, we provide a summary review on a number of NPS for which the neuropharmacological evaluation has made important progress in recent years. They include mitragynine ("Kratom"), synthetic cannabinoids (e.g., "Spice"), dimethyltryptamine and novel serotonergic hallucinogens, the cathinones mephedrone and methylone, ketamine and novel dissociative drugs, γ-hydroxybutyrate, γ-butyrolactone, and 1,4-butanediol. This review shows not only emerging harm potentials but also some potential medical applications.

The Neurobiological Mechanisms of Gamma-Hydroxybutyrate Dependence and Withdrawal and Their Clinical Relevance: A Review

OBJECTIVE

x03B3;-Hydroxybutyrate (GHB) has gained popularity as a drug of abuse. In the Netherlands the number of patients in treatment for GHB dependence has increased sharply. Clinical presentation of GHB withdrawal can be life threatening. We aim, through this overview, to explore the neurobiological pathways causing GHB dependency and withdrawal, and their implications for treatment choices.

METHODS

In this work we review the literature discussing the findings from animal models to clinical studies focused on the neurobiological pathways of endogenous but mainly exogenous GHB.

RESULTS

Chronic abuse of GHB exerts multifarious neurotransmitter and neuromodulator effects on x03B3;-aminobutyric acid (GABA), glutamate, dopamine, serotonin, norepinephrine and cholinergic systems. Moreover, important effects on neurosteroidogenesis and oxytocin release are wielded. GHB acts mainly via a bidirectional effect on GABAB receptors (GABABR; subunits GABAB1 and GABAB2), depending on the subunit of the GIRK (G-protein-dependent ion inwardly rectifying potassium) channel involved, and an indirect effect of the cortical and limbic inputs outside the nucleus accumbens. GHB also activates a specific GHB receptor and β1-subunits of α4-GABAAR. Reversing this complex interaction of neurobiological mechanisms by the abrupt cessation of GHB use results in a withdrawal syndrome with a diversity of symptoms of different intensity, depending on the pattern of GHB abuse.

CONCLUSION

The GHB withdrawal symptoms cannot be related to a single mechanism or neurological pathway, which implies that different medication combinations are needed for treatment. A single drug class, such as benzodiazepines, gabapentin or antipsychotics, is unlikely to be sufficient to avoid life-threatening complications. Detoxification by means of titration and tapering of pharmaceutical GHB can be considered as a promising treatment that could make polypharmacy redundant.

Succinate, an intermediate in metabolism, signal transduction, ROS, hypoxia, and tumorigenesis

Succinate is an important metabolite at the cross-road of several metabolic pathways, also involved in the formation and elimination of reactive oxygen species. However, it is becoming increasingly apparent that its realm extends to epigenetics, tumorigenesis, signal transduction, endo- and paracrine modulation and inflammation. Here we review the pathways encompassing succinate as a metabolite or a signal and how these may interact in normal and pathological conditions.(1).

The behavioural profile of gamma-hydroxybutyrate, gamma-butyrolactone and 1,4-butanediol in humans

Gamma-hydroxybutyrate (GHB) is a putative neurotransmitter, a drug of abuse, and a medical treatment for narcolepsy and other neuropsychiatric disorders. Its precursors gamma-butyrolactone (GBL) and 1,4-butanediol (1,4-BD) are endogenously converted to GHB and thereby exert their psychobehavioural effects. In humans, GHB has a wide spectrum of properties ranging from stimulation and euphoria in lower doses, to sedation, deep sleep, and coma after ingestion of high doses. However, behavioural studies in healthy volunteers remain scarce and are usually limited to psychomotor performance testing. Most available data arise from either qualitative studies with illicit users or clinical trials examining therapeutic properties of GHB (then usually termed sodium oxybate). Here, we present an overview of the behavioural effects of GHB, GBL, and 1,4-BD in these three populations. GHB and its precursors strongly influence behaviours related to core human autonomic functions such as control of food intake, sexual behaviour, and sleep-wake regulation. These effects are instrumentalised by illicit users and clinically utilised in neuropsychiatric disorders such as narcolepsy, fibromyalgia, and binge-eating syndrome. Considering the industry withdrawal from psychopharmacology development, repurposing of drugs according to their behavioural and clinical profiles has gained increasing relevance. As such, GHB seems to be an attractive candidate as an experimental therapeutic in depression.

GHB pharmacology and toxicology: acute intoxication, concentrations in blood and urine in forensic cases and treatment of the withdrawal syndrome

The illicit recreational drug of abuse, γ-hydroxybutyrate (GHB) is a potent central nervous system depressant and is often encountered during forensic investigations of living and deceased persons. The sodium salt of GHB is registered as a therapeutic agent (Xyrem®), approved in some countries for the treatment of narcolepsy-associated cataplexy and (Alcover®) is an adjuvant medication for detoxification and withdrawal in alcoholics. Trace amounts of GHB are produced endogenously (0.5-1.0 mg/L) 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). Available information indicates that GHB serves as a neurotransmitter or neuromodulator in the GABAergic system, especially via binding to the GABA-B receptor subtype. Although GHB is listed as a controlled substance in many countries abuse still continues, owing to the availability of precursor drugs, γ-butyrolactone (GBL) and 1,4-butanediol (BD), which are not regulated. After ingestion both GBL and BD are rapidly converted into GHB (t½ ~1 min). The Cmax occurs after 20-40 min and GHB is then eliminated from plasma with a half-life of 30-50 min. Only about 1-5% of the dose of GHB is recoverable in urine and the window of detection is relatively short (3-10 h). This calls for expeditious sampling when evidence of drug use and/or abuse is required in forensic casework. The recreational dose of GHB is not easy to estimate and a concentration in plasma of ~100 mg/L produces euphoria and disinhibition, whereas 500 mg/L might cause death from cardiorespiratory depression. Effective antidotes to reverse the sedative and intoxicating effects of GHB do not exist. The poisoned patients require supportive care, vital signs should be monitored and the airways kept clear in case of emesis. After prolonged regular use of GHB tolerance and dependence develop and abrupt cessation of drug use leads to unpleasant withdrawal symptoms. There is no evidence-based protocol available to deal with GHB withdrawal, apart from administering benzodiazepines.

Gamma-hydroxybutyrate enhances mood and prosocial behavior without affecting plasma oxytocin and testosterone

Gamma-hydroxybutyrate (GHB) is a GHB-/GABAB-receptor agonist. Reports from GHB abusers indicate euphoric, prosocial, and empathogenic effects of the drug. We measured the effects of GHB on mood, prosocial behavior, social and non-social cognition and assessed potential underlying neuroendocrine mechanisms. GHB (20mg/kg) was tested in 16 healthy males, using a randomized, placebo-controlled, cross-over design. Subjective effects on mood were assessed by visual-analogue-scales and the GHB-Specific-Questionnaire. Prosocial behavior was examined by the Charity Donation Task, the Social Value Orientation test, and the Reciprocity Task. Reaction time, memory, empathy, and theory-of-mind were also tested. Blood plasma levels of GHB, oxytocin, testosterone, progesterone, dehydroepiandrosterone (DHEA), cortisol, aldosterone, and adrenocorticotropic-hormone (ACTH) were determined. GHB showed stimulating and sedating effects, and elicited euphoria, disinhibition, and enhanced vitality. In participants with low prosociality, the drug increased donations and prosocial money distributions. In contrast, social cognitive abilities such as emotion recognition, empathy, and theory-of-mind, and basal cognitive functions were not affected. GHB increased plasma progesterone, while oxytocin and testosterone, cortisol, aldosterone, DHEA, and ACTH levels remained unaffected. GHB has mood-enhancing and prosocial effects without affecting social hormones such as oxytocin and testosterone. These data suggest a potential involvement of GHB-/GABAB-receptors and progesterone in mood and prosocial behavior.

Detection of gamma hydroxybutyrate in emergency department: Nice to have or a valuable diagnostic tool?

BACKGROUND

Many patients present to emergency departments (EDs) with an altered state of consciousness. Fast exclusion of gamma hydroxybutyrate (GHB)-associated intoxication in these patients may optimize diagnostic and therapeutic algorithms and decisions in the ED.

METHODS

Between January and March 2014, a novel enzymatic test system was used to quantify GHB in blood and urine samples of suspected intoxicated patients in the ED of the University Hospital. The underlying causes for suspected intoxication and the diagnostic and therapeutic measures were documented and analysed retrospectively.

RESULTS

GHB measurements were performed in 13 patients with suspected ingestion during a 3-month study period. GHB was positive in six patients showing serum levels between 61.8 mg/l and 254.8 mg/l, and GHB was tested negative in seven patients with a range of 0.3-6.2 mg/l (upper reference limit 6.1 mg/l). Additional intoxication was found in five of six GHB positive (83%, alcohol n = 2 and other drugs n = 5) and in six of seven negative-tested patients (86%, alcohol n = 5 and other drugs n = 1).

CONCLUSION

GHB quantification in the ED provides specific additional information for intoxication, which can lead to more precise diagnostic and therapeutic decisions and may also be important for legal aspects. We believe that GHB analysis in unconscious patients with suspected intoxication may improve the efficient treatment of intoxicated patients.

Increasing use of 'party drugs' in people living with HIV on antiretrovirals: a concern for patient safety

Use of 'party drugs', a particular set of recreational drugs used in the context of 'ChemSex', is frequent among MSM living with HIV. A recently published observational study showed that more than half of HIV-infected MSM interviewed reported use of illicit substances in the previous 3 months, with frequent concomitant use of three or more drugs. These substances are a combination of 'club drugs' (methylenedioxymethamphetamine, gamma-hydroxybutyrate, ketamine, benzodiazepine) and drugs that are more specifically used in a sexualized context (methamphetamine, mephedrone, poppers and erectile dysfunction agents). Although formal data on pharmacokinetic or pharmacodynamic interactions between recreational drugs and antiretroviral agents are lacking, information regarding potentially toxic interactions can be theorized or sometimes conclusions may be drawn from case studies and cohort observational studies. However, the risk of coadministering party drugs and antiretrovirals should not be overestimated. The major risk for a drug-drug interaction is when using ritonavir-boosting or cobicistat-boosting agents, and maybe some nonnucleoside reverse transcriptase inhibitors. Knowledge of the metabolic pathways of 'party drugs' may help in advising patients on which illicit substances have a high potential for drug-drug interactions, as this is not the case for all.

Metabolism of gamma hydroxybutyrate in human hepatoma HepG2 cells by the aldo-keto reductase AKR1A1

Gamma hydroxybutyrate (GHB) is a recreational and date-rape drug, for which the detection following ingestion is hampered by rapid metabolism and its endogenous presence. GHB catabolism occurs mainly by its oxidation to succinic semialdehyde (SSA), which converts to succinate and enters the tricarboxylic acid cycle. A high Km aldehyde reductase has previously been reported to catalyse the NADP-dependent oxidation of GHB at high concentrations. It is assumed that this enzyme is identical to the aldo-keto reductase AKR1A1, but its role in GHB oxidation has not been fully evaluated. In this study, the extent of AKR1A1 in GHB metabolism has been determined in HepG2 cells using RNA-interference technology. The gene encoding AKR1A1 was targeted by siRNA. Results demonstrate a successful knock-down of the AKR1A1 gene with 92% reduction in total mRNA and 93% reduction in protein expression. Demolishing AKR1A1 expression in HepG2 cells leads to significant 82% decrease in NADP-dependent GHB-dehydrogenase activity at high concentration (10mM) of GHB. Moreover, when exposing the cells to 50 μM of GHB for 24h, and measuring intracellular and extracellular GHB levels by GC/MS, a significant two-fold increase was observed on GHB intracellular level in silenced cells. In contrast, measuring SSA-reductase activity in silenced cells indicated that AKR1A1 is not involved in endogenous GHB production. These findings describe a pathway for GHB metabolism in the liver which should be useful in GHB exposure cases, and will enable a better understanding of the enzymes participating in its metabolism at natural and overexposed levels.

Risk assessment of GBL as a substitute for the illicit drug GHB in the Netherlands. A comparison of the risks of GBL versus GHB

In the Netherlands, γ-hydroxybutyric acid (GHB) was recently banned, but γ-butyrolactone (GBL) was not. As such, GBL remained a legal alternative to GHB. This review compares the risks of GBL and GHB. Pure GBL is per unit of volume about threefold stronger and therefore threefold more potent than currently used GHB-preparations in the Netherlands. Like GHB, GBL use hardly leads to organ toxicity, although, as with GHB, frequent GBL use may lead to repeated comas that may result in residual impairments in cognitive function and memory. Little is known about the prevalence of GBL use in Europe, but the recent increase in improper trading in GBL confirms that users of GHB gradually switch to the use of GBL. This shift may result in an increase in the number GBL dependent users, because the dependence potential of GBL is as great as that of GHB. Severe withdrawal symptoms and a high relapse rate are seen following cessation of heavy GBL use. GBL-dependent users seem to be severe (dependent, problematic) GHB users who started using GBL, the legal GHB substitute. Subjects who are solely dependent to GBL are rarely reported. About 5-10% of the treatment seeking GHB dependent subjects also use GBL and this subpopulation forms a vulnerable group with multiple problems. Fatal accidents with GBL are rarely reported, but non-fatal GHB (or GBL) overdoses frequently occur for which supportive treatment is needed. It is recommended to monitor the recreational use of GBL, the rate of GBL dependence treatment, and the improper trading of GBL.