Gamma-hydroxybutyrate Concentrations Research Articles

In Vitro Production of Gamma-Hydroxybutyrate in Antemortem Blood Under Various Storage Conditions.

Gamma-hydroxybutyrate (GHB) is an endogenous compound and central nervous system depressant drug used recreationally for its intoxicating effects. In a medico-legal context, the interpretation of blood GHB concentrations can be complicated by its endogenous nature and potential for formation during storage. In Canada, the per se limit for GHB in blood is 5 mg/L. Endogenous GHB concentrations in blood are typically well below 5 mg/L; however, there is a paucity of literature regarding the potential production of GHB in antemortem blood during storage. Changes in GHB concentrations were evaluated over the course of 306 days in preserved and unpreserved antemortem blood stored at 4°C and 21°C. Results were compared to 22 impaired driving cases in Ontario between 2019-2022 where GHB was detected in antemortem blood by toxicological analysis at the Centre of Forensic Sciences. Preservative was effective at minimizing GHB production (< 2.5 mg/L) regardless of storage temperature whereas significant in vitro production of GHB occurred in unpreserved antemortem blood. GHB production occurred rapidly in unpreserved blood stored at 21°C; a significant increase was detected after 5 days. The rate of GHB production in unpreserved blood stored at 4°C occurred more gradually but increased significantly by day 30 and reached a maximum concentration of 10 mg/L at 114 days. In unpreserved blood, GHB concentrations were significantly lower at 4°C compared to 21°C for the first 44 days; however, refrigeration had no significant effect then onward. Blood concentrations of GHB detected in the majority of impaired driving cases were markedly higher than the maximum concentration of 10 mg/L detected in the study; however, in 4 of the 22 cases, concentrations were below 10 mg/L. The results demonstrate that concentrations of GHB less than 10 mg/L in blood collected for the purposes of a drug impaired driving investigation should be carefully interpreted.

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).

Characteristics of analytically confirmed gamma-hydroxybutyrate (GHB) positive patients in the emergency department: presentation, poly-drug use, disposition and impact on intensive care resource utilisation

Background Gamma-hydroxybutyrate is a potent central nervous system depressant with a narrow recreational dose window and analytical detection time. We describe data relating to intoxicated patients presenting to emergency departments across metropolitan Adelaide who tested positive for gamma-hydroxybutyrate. This work was part of the Emergency Department Admission Blood Psychoactive Testing study. Methods Over a 15-month period, patients presenting to four metropolitan emergency departments with symptoms of drug intoxication were enrolled in the study. The methodology involved the collection of demographic and clinical data and a de-identified blood sample which underwent comprehensive toxicological analysis. Gamma-hydroxybutyrate was determined using an acid-catalysed cyclisation followed by liquid-liquid extraction and gas chromatography-mass spectrometry. Data relating to samples positive for gamma-hydroxybutyrate were examined. Results and discussion A total of 1120 patients were enrolled between March 2019 and May 2020, 309 of whom were positive for gamma-hydroxybutyrate (27.6%). Of these, 256 (83%) were also positive for metamfetamine (methamphetamine). The most common clinical observation in gamma-hydroxybutyrate-positive patients was central nervous system depression (89%). There was a significant relationship between gamma-hydroxybutyrate status and sex; although males outnumbered females in absolute terms, a higher proportion of females (32%) tested positive for gamma-hydroxybutyrate than males (25%, P = 0.0155). Blood gamma-hydroxybutyrate concentrations ranged from 10 to 651 mg/L (0.096–6.2 mmol/L) and increasing gamma-hydroxybutyrate concentration correlated with severe toxicity. The presence of gamma-hydroxybutyrate had a significant impact on the patient discharge destination: the majority (69.2%) of gamma-hydroxybutyrate-positive patients were managed and discharged from the emergency department or their attached short stay wards. A significantly higher proportion of gamma-hydroxybutyrate-positive patients were admitted to the intensive care unit (28.2%) compared with gamma-hydroxybutyrate-negative patients (12.7%, chi-squared = 36.85, P <0 .001). Gamma-hydroxybutyrate positive cases accounted for 45.8% of all study-related intensive care unit admissions. Conclusions Gamma-hydroxybutyrate is commonly detected in illicit drug-related emergency department presentations and is detected disproportionately in the patient cohort who require intensive care unit level care.

Detection of Exogenous γ-Hydroxybutyric Acid in Rat Blood Exosomes.

To find a method to distinguish exogenous gamma-hydroxybutyrate (GHB) from endogenous GHB by establishing ultra-high performance liquid chromatography-mass spectrometry (UPLC-MS) based on exosome for quantitative detection of GHB in the rat blood. Adult male SD rats were divided into 1 h, 5 h, 10 h administration group and control group. After 1 h, 5 h and 10 h of single precursor of GHB gamma-butyrolactone (GBL) intraperitoneal injection in administration groups, 5 mL blood was collected from the abdominal aorta. Meanwhile, the control group was given a same dose of normal saline, and 5 mL blood was collected at 1 h. Among the 5 mL blood, 0.5 mL was directly detected by HPLC-MS after pretreatment, and exosomes were extracted from the remaining blood by differential centrifugation and detected. The concentration of GHB in the control group was (87.36±33.48) ng/mL, and the concentration with administration at 1 h, 5 h and 10 h was (110 400.00±1 766.35) ng/mL, (1 479.00±687.01) ng/mL and (133.60±12.17) ng/mL, respectively. The results of exosome detection showed that no peak GHB signal was detected in the control group and the 10 h administration group, and the concentrations of GHB at 1 h and 5 h administration groups were (91.47±33.44) ng/mL and (49.43±7.05) ng/mL, respectively. GHB was detected in blood exosome by UPLC-MS, which indicated that exogenous GHB could be detected in plasma exosomes, while endogenous GHB could not be detected, suggesting that this method may be used as a basis to determine whether there is exogenous drug intake.

Effect of body refrigeration on the postmortem formation of gamma hydroxybutyrate in whole blood

Gamma hydroxybutyrate (GHB) levels in biological fluids are known to be increased after death. To date, there have been studies on sample storage conditions and preservatives on the postmortem in vitro formation of GHB. However, only few studies explored the effects of body storage conditions on GHB formation after death. In this study, we determined the effect of body refrigeration during body storage in mortuary refrigerators on postmortem formation of GHB in whole blood samples. A total of 41 fatalities were divided into two groups: Group A with a total refrigeration time less than 10 h and Group B with a total body refrigeration time more than 10 h. Femoral blood was collected 3 times: upon arrival at the mortuary, after 4 h of refrigeration, and at autopsy. Rectal temperatures were recorded at the time of specimen collection. Blood GHB concentration was analyzed by LC-MS/MS. The rate of change in GHB levels was calculated. The study revealed that in the later phase of refrigeration, no difference was observed in the blood GHB levels between the two groups despite differences in the postmortem interval (PMI) and refrigeration time. Moreover, the rate of change in the GHB levels was lower in the group with a longer refrigeration time. Hence, we concluded that once the plateau of postmortem GHB formation is reached in a refrigerated body, further formation is not expected even with prolonged PMI. Early body refrigeration can minimize postmortem GHB production, thereby preventing the incorrect interpretation of analytical results.

Levels of GHB in hair after regular application

Gamma hydroxybutyrate (GHB) is a central nervous system depressant that is an approved drug for the treatment of narcolepsy with cataplexy and other syndromes. Due to its dose dependent stimulating, relaxing or sedative effects, illicit abuses include recreational use by young people and cases of drug-facilitated crime (DFC). Since GHB is also produced endogenously, for forensic questions, it is important to be able to differentiate between endogenous GHB and elevated levels due to additional intake. In this study, we measured GHB concentrations in hair of patients with narcolepsy receiving daily GHB treatment. The results were compared to endogenous concentrations and concentrations after chronic intake presented in several former studies. The aim of this study was to investigate whether a regular intake of a known dosage of GHB leads to elevated levels of GHB concentration in hair. We collected hair samples of 19 patients (14 female, 5 male) with narcolepsy under regular GHB treatment and examined the hair samples segmentally by digestion of the hair followed by liquid-liquid extraction and analysis using a Shimadzu LC20 UFLC system coupled with an AB Sciex API 4000 Qtrap tandem mass spectrometer. All volunteers received daily treatment with different doses of sodium oxybate (sodium salt of GHB) ranging between 3 and 9g per night. The observed mean value of GHB concentration in hair was 2.69ng GHB per mg hair for the 5 male participants, 1.56ng/mg for the 14 female participants giving an overall mean value of 1.86ng/mg for all participants. Our results showed no correlation between the daily dose or the duration intake of GHB and the measured concentration of GHB in hair. Although we did find a significant (p<0.01) difference between published endogenous levels of GHB in hair and GHB levels in hair of patients with regular daily GHB intake, the forensic relevance however is disputable. We hypothesise this narrow margin or even overlap to be the reason why analytical results from hair analysis in some cases fail to provide a reliable prove of a single exposition.

Method Validation of Gamma-Hydroxybutyrate Detection upon Herpes Simplex Virus-Type 1 Infection using LC-MRM-MS with 3-Nitrophenylhydrazine Derivatization

Volatile organic compounds (VOCs) release triggered by infection of DNA virus has not been studied extensively. Previously, we reported that gamma-butyrolactone (GBL), a VOC, was released upon Herpes Simplex Virus Type-1 (HSV-1) acute infection. Based on the metabolic pathway and chemical conversion of GBL, we hypothesized that infected cells produce gammahydroxybutyrate (GHB) as a key pathway intermediate for the subsequent production of GBL. An analytical technique for the rapid detection of GHB is crucial for further understanding its role in the cellular response to HSV-1 infection. To address this, we developed a sensitive, reliable and specific method for the detection and quantification of GHB in mammalian cell culture using a pre-column derivatization approach. Our data showed that the carboxylic acid functional group of GHB could be derivatized with 3-nitrophenylhydrazine hydrochloride (3NPH) to produce its hydrazineyl derivative. Unlike GHB, the derivative could be detected seamlessly in HPLC-MS. We also demonstrate quantitive conversion of GHB into the derivative with over 95% yield at a range of 1 μg/mL- 6 μg/mL GHB concentration. This method offers a rapid quantification of GHB in aqueous mixtures, especially in cultured extracts.

0743 The Pharmacokinetic Adverse Event Relationship for FT218, a Once-Nightly Sodium Oxybate Formulation

Abstract Introduction Sodium oxybate is an effective treatment for excessive daytime sleepiness and cataplexy in patients with narcolepsy. The approved formulation requires twice-nightly dosing: at bedtime and 2.5 - 4 hours later, which results in two distinct Cmax’s. FT218 is a controlled-release formulation of sodium oxybate intended for once-nightly dosing, using Avadel’s proprietary Micropump™ technology. The objective of this study was to evaluate the pharmacokinetic-adverse event (AE) relationship for FT218, an investigational once-nightly sodium oxybate formulation. Methods Six single-dose, randomized, crossover studies that assessed the pharmacokinetics of FT218 at 4.5, 6, 7.5 and 9 g in healthy voluntters were used in this analysis. Lattice plots, “spaghetti” plots, and scatter plots of individual gamma hydroxybutyrate concentrations and indicators when AEs by system, organ, or class (SOC) were created to determine any PK-AE relationship. Results A total of 129 healthy volunteers received single doses of FT218 between 4.5 - 9 g. Most AEs, specifically for the neurological and gastrointestinal SOC, occurred close to Tmax, during the Cmax period, which for FT218 was around 1.5-2 hours after dosing. These AEs were known AEs associated with sodium oxbyate. There appeared to be no clear correlation between individual plasma GHB concentrations levels and AEs between subjects. Individual AEs were equally distributed above and below the mean population Cmax and AUCinf for the dataset. Conclusion In general, adverse events for FT218 occurred around Tmax. There was no clear population toxicokinetic range for when AEs occur with FT218, but mostly individual thresholds. Since it appears AEs are related to Cmax, and FT218 only has one Cmax compared to two with the currently available product, it is hypothesized that FT218 will have a favorable safety profile compared to twice-nightly dosing. Support This work was supported by Avadel Pharmaceuticals

The challenge of post-mortem GHB analysis: storage conditions and specimen types are both important.

For the interpretation of concentrations of gamma-hydroxybutyrate (GHB) in post-mortem specimens, a possible increase due to post-mortem generation in the body and in vitro has to be considered. The influence of different storage conditions and the specimen type was investigated. Post-mortem GHB concentrations in femoral venous blood (VB), heart blood (HB), serum (S) from VB, urine (U), cerebrospinal fluid (CSF) and vitreous humour (VH) were determined by gas chromatography-mass spectrometry after derivatisation. Various storage conditions, that is 4°C or room temperature (RT) and the addition of sodium fluoride (NaF), were compared during storage up to 30days. Additionally, bacterial colonisation was determined by mass spectrometry fingerprinting. Twenty-six cases without involvement of exogenous GHB were examined. GHB concentrations (by specimen) at day0 were 3.9-22.1mg/L (VB), 6.6-33.3mg/L (HB), < 0.5-18.1mg/L (U), 1.1-10.4mg/L (CSF) and 1.7-22.0mg/L (VH). At 4°C, concentrations increased at day30 to 5.6-74.5mg/L (VB), 4.6-76.5mg/L (HB) and < 0.5-21.3mg/L (U). At RT, concentrations rose to < 0.5-38.5mg/L (VB), 1.2-94.6mg/L (HB) and < 0.5-37.5mg/L (U) at day30. In CSF, at RT, an increase up to < 0.5-21.2mg/L was measured, and at 4°C, a decrease occurred (< 0.5-6.5mg/L). GHB concentrations in VH remained stable at both temperatures (1.2-20.9mg/L and < 0.5-26.2mg/L). The increase of GHB in HB samples with NaF was significantly lower than that without preservation. No correlation was found between the bacterial colonisation and extent of GHB concentration changes. GHB concentrations can significantly increase in post-mortem HB, VB and U samples, depending on storage time, temperature and inter-individual differences. Results in CSF, VH, S and/or specimens with NaF are less affected.

The prevalence of gamma-hydroxybutyrate (GHB) in motor vehicle drivers and its co-administration with amphetamine type substances (ATS) in Queensland, Australia (2011–2018)

The routine analysis of driver specimens for gamma-hydroxybutyrate (GHB) is rarely performed by toxicology laboratories as the physical and chemical properties of GHB make it unamenable to the screening methods usually employed. The prevalence of the drug in driver populations has therefore only rarely been reported. This study outlines the results of the routine analysis for GHB in the blood of motor vehicle drivers in Queensland, Australia, over an eight-year period (2011–2018).The methodology for GHB analysis was updated over the course of the study; screening for GHB was conducted using GC/FID or GC/MS between 2011 and 2016 and by LC/MS/MS from 2017 onwards. Due to the endogenous nature of GHB, any specimens containing greater than 5mg/kg GHB were subjected to quantitative analysis by either; GC/MS after liquid-liquid extraction and derivatisation with BSTFA+1%TMCS (2011–2016), or by LC/MS/MS analysis after solvent precipitation from 2017 onwards.Of the 15,061 specimens analysed, 160 were positive for GHB (1.1% of all cases, range 0.4–1.8%). GHB positive drivers were 66.9% male (33.1% female) and had an average age of 32 years. The mean GHB concentration identified was 89mg/kg (range 6–354mg/kg).GHB was found to be closely associated with amphetamine type substances (ATS), particularly methylamphetamine. Though GHB was present in only 2.2% of all ATS positive specimens submitted to the laboratory, 91.2% of all GHB positive cases contained an ATS. Other drugs commonly co-administered with GHB were THC, cocaine, benzodiazepines and erectile dysfunction drugs. GHB was found to be more commonly identified in drivers from city areas and a geographical localisation of the use of the drug was identified in the Gold Coast region of Queensland.

Relationship Between Postmortem Urine and Blood Concentrations of GHB Furnishes Useful Information to Help Interpret Drug Intoxication Deaths.

This article reports the concentrations of gamma-hydroxybutyrate (GHB) in femoral blood and bladder urine in a case series of drug intoxication deaths (N = 37). GHB was determined in blood (B-GHB) and urine (U-GHB) by a GC-FID-GBL method and 30 mg/L was used as a cut-off concentration for reporting positive results. The mean (median) and range of GHB concentrations in bladder urine were 2,818 mg/L (1,900 mg/L) and 120-13,000 mg/L, respectively. These concentrations were appreciably higher than those in femoral blood, 637 mg/L (260 mg/L) and 30-9,200 mg/L, respectively. Urine/blood ratios of GHB were highly variable (mean 8.99, median 5.33 and range 0.16-29.3). GHB is rapidly metabolized and cleared from the bloodstream, whereas there is no metabolism occurring in the urinary bladder. In five autopsy cases, U-GHB was lower than B-GHB, which suggests that these individuals died before equilibration of the drug in all body fluids and tissues. In the other 32 deaths, U-GHB was higher than B-GHB, sometimes appreciably higher, which points towards a longer survival time after intake or administration of GHB. The analysis of urine extends the window of detection of GHB by several hours compared with blood samples, depending in part on when the bladder was last voided before death. Furthermore, the urinary concentration of GHB gives a hint about the concentration in blood during the time that the urine was produced in the kidney and stored in the bladder since the previous void.

Postmortem concentrations of gamma-hydroxybutyrate (GHB) in peripheral blood and brain tissue — Differentiating between postmortem formation and antemortem intake

Gamma-hydroxybutyrate (GHB) is a recreational drug, a drug of abuse, as well as an endogenous molecule in mammals. The drug has become infamous as a tool for drug-facilitated sexual assault. GHB is found in low concentrations in living humans, while at postmortem the concentration of GHB rises due to fermentation processes. The endogenous nature of GHB leads to difficulty in interpretation of concentrations, as the source of GHB is not obvious.Postmortem brain and blood samples were collected from 221 individuals at autopsy. Of these, 218 were not suspected of having ingested GHB, while GHB intake was reported for the last three (cases A–C). Decomposition level was estimated and cases classified into no/minor and advanced decomposition. Brain samples were extracted from the frontal lobe; only gray matter from the cerebral cortex was used. Blood was drawn from the femoral vein. Brain samples were homogenized and diluted with water. Brain homogenates or femoral blood were then prepared using protein precipitation and GHB was quantified with UHPLC–MS/MS.For 189 cases where ingestion of GHB was not suspected and where no/minor decomposition had occurred the concentrations were in the range 4.8–45.4mg/kg (median 15.3mg/kg) in blood and not-detected to 9.8mg/kg (median 4.8mg/kg) in brain tissue. For case A, where intoxication with GHB was deemed to be the sole cause of death, the concentrations were 199 and 166mg/kg in blood and brain, respectively. For case B, where intoxication with GHB was a contributing factor of death, the respective concentrations were 142 and 78.4mg/kg. For case C, where GHB was ingested but the cause of death was opioid poisoning, the concentrations were 40.3 and 12.7mg/kg.The results demonstrate that postmortem-formed levels of GHB are much lower in brain than peripheral blood. Analysis of GHB in brain tissue thus provides for an improved capability to identify an exogenous source of GHB. By measuring GHB in brain tissue and employing a cut-off concentration of 10mg/kg, a tentative distinction can be made between an endo- and exogenous source of GHB. An exception to this strategy is for extensively decomposed corpses, where endogenous GHB concentrations can be high even in brain.

Increases in Serum Growth Hormone Concentrations Associated with GHB Administration.

The administration of gamma-hydroxybutyrate (GHB) has been reported to augment the increase in growth hormone (GH) secretion associated with the onset of sleep. The ability of GHB to stimulate GH production in the absence of sleep in both male and female volunteers was investigated as part of a GHB administration study. Twelve healthy volunteers (six men and six women) were given a small oral dose (25 mg/kg) of GHB (as Xyrem®) at 10:00 h. Basal blood samples (as serum) were taken 10 min prior to GHB administration, with additional samples taken at 10, 15, 20, 25, 30, 45, 60, 90, 120, 150, 180, 240, 360 and 480 min post-administration. The serum concentrations of GHB were measured by GC-MS and GH by immunometric assay. Following GHB administration, volunteers exhibited effects consistent with mild sedation, i.e., relaxed with normal responses to verbal stimuli. Despite none being asleep, an increase in serum GH concentration occurred in 11 out of the 12 volunteers (5 women and 6 men). In these volunteers, peak GH concentrations occurred 45-60 min post-administration compared with a mean serum tmax for GHB of 23 min (SD = 5.4 min). The absolute increase in GH was similar formen and women, averaging 3.4 and 3.7 ng/mL, respectively. The mean intra-individual increase in GH was much greater in males (29 times) compared with females (2 times), as males had (as expected) smaller basal GH concentrations (mean = 0.26 ng/mL) compared with females (mean = 5.4 ng/mL). After maximizing, the GH concentration decreased rapidly (in agreement with GHB concentrations), returning to basal concentrations at ~90-120 min post-administration. GHB administration at a small therapeutic dose results in increases in serum GH concentrations in healthy male and female volunteers in the absence of sleep onset.

Quantitative analysis of the endogenous GHB level in the hair of the Chinese population using GC/MS/MS

Endogenous production complicates interpretation when gamma-hydroxybutyrate (GHB) is measured in hair for forensic purposes. A method capable of quantifying the endogenous concentration of GHB in human head hair was developed and validated using GC/MS/MS. Hair was digested under alkaline conditions (1 mol/L NaOH, 90 °C 10 min), and GHB-d6 was used as an internal standard. Before derivatization with BSTFA and ethyl acetate, a liquid–liquid extraction with ethyl acetate under acidic conditions was performed. GHB-TMS derivatives were detected using GC/MS/MS in the multiple-reaction monitoring mode. This method exhibited good linearity (y = 0.018x + 0.038, R2 = 0.9998), and the limit of detection was 0.02 ng/mg. The extraction recoveries were more than 60%, and the inter-day and intra-day relative standard deviations (RSD) were less than 15%. This method has been applied for the analysis of the endogenous GHB in hair samples from 66 drug-free Chinese donors. The mean measured concentration for 0–3 cm hair was 1.93 ± 1.40 ng/mg (n = 66), and extreme values were in the range of 0.28–4.91 ng/mg. The mean male endogenous GHB level was 2.95 ng/mg (0.92–4.91 ng/mg, n = 35), while the mean female level was 0.77 ng/mg (0.28–1.95 ng/mg, n = 31). This method was applied to a forensic case for the determination of GHB in hair samples but it is hard to make a reasonable “cut off” in hair. The solution is to use each subject as his own control.

Endogenous concentrations of GHB in postmortem blood from deaths unrelated to GHB use.

Gamma-hydroxybutyrate (GHB) is an endogenous compound, but its presence in postmortem blood presents a challenge when interpreting elevated levels as GHB is misused as a recreational drug and is also produced postmortem. A total of 387 postmortem cases (273 male and 114 female) submitted to the toxicology laboratory between 2010 and 2012 specifically requested the analysis of the ketoacidosis biomarker, beta-hydroxybutyrate (BHB). No reference to GHB use was identified in any of the case files; however, BHB and GHB are measured simultaneously using deuterated GHB as the internal standard (GHB-d6) within a calibration range of 5-500 mg/L. GHB was not detected or <10 mg/L in 18% of the cases (n = 68), between 10 and 50 mg/L in 73% of the cases (n = 283) and between 51 and 193 mg/L in 9% of the cases (n = 36). The manner of death was classified as accidental (n = 11), alcohol-related (n = 237), drug-related (n = 23), homicide (n = 1), natural (n = 91), suicide (n = 9), medical-related (n = 1) and undetermined (n = 14). Six cases had GHB concentrations in excess of 100 mg/L with advanced decomposition changes noted in five of these cases. Moderate-to-advanced decomposition was also noted in 50% (n = 15) of the cases with GHB concentrations in excess of 50 mg/L but <100 mg/L. Approximately one-third of the blood samples tested contained a preservative and although a higher proportion of these samples had GHB concentrations <10 mg/L or not detected (∼30% preserved versus 11% unpreserved), there were still cases with GHB concentrations >51 mg/L (∼6% preserved versus 11% unpreserved). This study highlights the danger of only using a cutoff to establish endogenous levels compared with exogenous use of GHB in postmortem blood.

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 50μM 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.

Post mortem concentrations of endogenous gamma hydroxybutyric acid (GHB) and in vitro formation in stored blood and urine samples

Gamma-hydroxybutyrate (GHB) is a central nervous system depressant, primarily used as a recreational drug of abuse with numerous names. It has also been involved in various instances of drug-facilitated sexual assault due to its potential incapacitating effects.The first aim of this paper is to measure the post-mortem concentration of endogenous GHB in whole blood and urine samples of 30 GHB free-users, who have been divided according to the post-mortem interval (PMI) in three groups (first group: 24–36h; second group: 37–72h; third group: 73–192h), trying to evaluate the role of PMI in affecting post mortem levels. Second, the Authors have evaluated the new formation of GHB in vitro in blood and urine samples of the three groups, which have been stored at −20°C, 4°C and 20°C over a period of one month.The concentrations were measured by GC–MS after liquid–liquid extraction according to the method validated and published by Elliot (For. Sci. Int., 2003). For urine samples, GHB concentrations were creatinine-normalized.In the first group the GHB mean concentration measured after autopsy was: 2.14mg/L (range 0.54–3.21mg/L) in blood and 3.90mg/g (range 0.60–4.81mg/g) in urine; in the second group it was: 5.13mg/L (range 1.11–9.60mg/L) in blood and 3.93mg/g (range 0.91–7.25mg/g) in urine; in the third group it was: 11.8mg/L (range 3.95–24.12mg/L) in blood and 9.83mg/g (range 3.67–21.90mg/g) in urine.The results obtained in blood and urine samples showed a statistically significant difference among groups (p<0.001) in the first analysis performed immediately after autopsy.Throughout the period of investigation up to 4 weeks, the comparison of storage temperatures within each group showed in blood and urine samples a mean difference at 20°C compared to −20°C not statistically significant at the 10% level.These findings allow us to affirm that the PMI strongly affects the post mortem production of GHB in blood and urine samples. Regarding the new formation of GHB in vitro both in blood and urine samples of the three groups, which have been stored at −20°C, 4°C and 20°C over a period of one month, although there was no significant increases of GHB levels throughout the period of investigation, the lowest increases were found both in blood and urine at −20°C, therefore we recommend the latter as optimal storage temperature.

Gamma-hydroxybutyrate (GHB) and topiramate—clinically relevant drug interaction suggested by a case of coma and increased plasma GHB concentration

Gamma-hydroxybutyrate (GHB) and topiramate—clinically relevant drug interaction suggested by a case of coma and increased plasma GHB concentration

Detection of gamma-hydroxybutyrate in hair: Validation of GC–MS and LC–MS/MS methods and application to a real case

A gas chromatography-mass spectrometry (GC-MS) and a liquid chromatography tandem mass spectrometry (LC-MS/MS) method were validated for quantifying endogenous and exogenous hair concentrations of gamma-hydroxybutyrate (GHB). The GC-MS method is based on overnight extraction of 25 mg hair in NaOH at 56 °C, liquid/liquid extraction in ethylacetate and trimethylsylil derivatization; analysis is by electron ionization and single ion monitoring of three ions. The LC-MS/MS method entails a rapid digestion of 25 mg hair with NaOH at 75 °C for 40 min, liquid/liquid extraction in ethylacetate and reconstitution of the extract in the LC mobile phase; negative ion electrospray ionization and multiple reaction monitoring (MRM) analysis are employed for the LC-MS/MS detection. In both cases, GHB-d6 is used as an internal standard. The endogenous amount in "blank" hair are estimated by the standard addition method. Limits of detection are 0.4 and 0.5 ng/mg for GC-MS and LC-MS/MS respectively, while the limit of quantification (LOQ) is 0.6 ng/mg for both methods; the GC-MS method proved to be linear in the range 1-50 ng/mg whereas linearity was demonstrated from 0.6 to 50 ng/mg for the LC-MS/MS; imprecision and inaccuracy were always lower than 23% for quality controls samples. The two methods were applied to a real case of a man addicted to GHB; the drug concentration in segments from 17 cm hair strand well correlated with self-reported use of GHB in different periods of his life. Performances of the two methods were similar.

Long-term stability of GHB in post-mortem samples and samples from living persons, stored at −20 °C, using fluoride preservatives

PurposeReanalyses are frequently requested in forensic toxicology, and knowledge of the stability of drugs in biological samples is of major importance for the interpretation of the toxicological findings. Currently, the literature on stability of gammahydroxybutyrate (GHB) in blood samples from living subjects and in post-mortem blood is limited. The purpose of this study was to evaluate the long-term stability of GHB in both blood samples from persons suspected of drug use and post-mortem blood samples. MethodsA total of 59 reanalyses were performed in whole blood samples, 27 samples from living subjects and 32 samples taken at autopsies. The samples were stored in the freezer between 0.4 and 7.2years at −20°C in vials containing preservatives. Analyses were performed by GC–FID, and cut-off level was 10.3mg/L. The concentrations in 22 of the samples were below cut-off. ResultsThe mean change in concentration between initial analysis and reanalysis was −0.8% for the positive samples from living persons and −7.1% for the positive post-mortem samples. Changes ranged from −32.4% to 21.0% for samples from living and from −30.4% to 34.4% for post-mortem samples. All negative samples were still negative at the time of reanalysis. ConclusionReanalysis of these forensic whole blood samples stored several years at −20°C with fluoride preservation did not exhibit changes in GHB concentrations of practical significance for the interpretation of toxicological findings.