Gamma-hydroxybutyrate serum levels and clinical syndrome after severe overdose

Pharmacokinetics of gamma-hydroxybutyric acid in 6-week-old swine (Sus scrofa domesticus) after intravenous and oral administration

Sedative as well as protective effects during hypoxia have been described for gamma-hydroxybutyric acid (GHB). Six swine (Sus scrofa domesticus) of 6 weeks old were administered NaGHB at a dose of 500 mg/kg intravenously (IV) and 500 and 750 mg/kg orally (PO) in a triple cross-over design. Repeated blood sampling was performed to allow pharmacokinetic analysis of GHB. Whole blood concentration at time point 0 after IV administration was 1727.21 ± 280.73 μg/mL, with a volume of distribution of 339.45 ± 51.41 mL/kg and clearance of 164.94 ± 47.05 mL/(kg h). The mean peak plasma concentrations after PO administration were 326.57 ± 36.70 and 488.01 ± 154.62 μg/mL for 500 mg/kg and 750 mg/kg, respectively. These were recorded at 1.42 ± 0.72 and 1.58 ± 0.58 h after PO dose for GHB 500 mg/kg and 750 mg/kg, respectively. The elimination half-life for IV and PO 500 mg/kg and PO 750 mg/kg dose was respectively 1.33 ± 0.30, 1.16 ± 0.31 and 1.11 ± 0.33 h. The bioavailability (F) for PO administration was 45%. No clinical adverse effects were observed after PO administration. Deep sleep was seen in one animal after IV administration, other animals showed head pressing and ataxia.

Complications in post-mortem GHB cut-off values in urine samples: A case report

Gamma-hydroxybutyric acid (GHB) is a drug of abuse, that interplays with a GABAergic system, resulting in an euphoric state and increased mood and impulses. Two cases of fatal mixed intoxications including GHB intake are presented here. In both cases, GHB was used together with multiple other drugs. Interpretation of GHB cut-off values are complicated in post-mortem analysis, because GHB can be post-mortem formed. The post-mortem GHB formation is dependent of the post-mortem interval (PMI) and the storage conditions of the samples. The GHB concentrations in urine are more stable compared to blood samples, when the samples are stored at the correct way at - 20 °C. Therefore, urine is the recommended matrix to analyze in toxicological screenings, since it allows more specific determination of exposure to exogenous GHB. Different cut-off values are used for matrices from living and deceased people. A cut-off value of 30 mg/L is recommended to discriminate between endogenous concentrations and concentrations resulting from exogenous GHB exposure. Moreover, post-mortem GHB formation can take place before sampling. However, when the samples are immediately stored at cooled conditions, no in vitro formation of GHB will take place. Urinary screening of GHB may serve as an initial screening for estimation of exposure of GHB in the body. However, additional quantitative GHB analysis in blood is required to estimate GHB exposure at the time of death. Furthermore, to obtain more reliable results for the ante-mortem GHB exposure, it may be useful to measure other biomarkers, like some GHB metabolites, especially in blood.

Characteristics and dose-effect relationship of clinical gamma-hydroxybutyrate intoxication: A case series

Gamma-Hydroxybutyrate (GHB) overdoses cause respiratory depression, coma, or even death. Symptoms and severity of poisoning depend on blood-concentrations and individual factors such as tolerance. A retrospective case study was conducted, evaluating GHB intoxication cases. GHB-concentrations in blood and urine were determined by gas chromatography-mass spectrometry (GC-MS) along with, in part, via enzymatic assay. GHB-concentrations, demographic data, and additional drug use, as well as specific clinical information, were evaluated. The correlation between GHB-levels in blood and associated symptoms were examined. In total, 75 cases originating from the Emergency Departments (EDs) of Hamburg and surrounding hospitals were included. Fifty-four of the patients (72%) were male. The mean GHB-concentration in blood was 248 mg/L (range 21.5-1418 mg/L). Out of the group with detailed clinical information (n = 18), the comatose group (n = 10/18) showed a mean of 244 mg/L (range 136-403 mg/L), which was higher than that of the somnolent and awake patients. Of the comatose collective, 70% (n = 7) showed co-use of one or more substances, with the additional use of cocaine being the most frequently detected (n = 5). In conclusion, a moderate dose-effect relationship was observed, although, there was some overlap in dosage concentration levels of GHB in awake and comatose patients. In GHB-intoxication cases, co-use was common as were clinical effects such as acidosis, hypotension, and impact on the heart rate. Timely analytical determination of the GHB-concentration in blood could support correct diagnosis of the cause of unconsciousness.

Safety of withholding intubation in gamma-hydroxybutyrate- and gamma-butyrolactone-intoxicated coma patients in the emergency department

OBJECTIVE

The objective of this study was to determine if supportive care without endotracheal intubation in the emergency department (ED) was safe in the absence of complications in gamma-hydroxybutyrate (GHB)/gamma-butyrolactone (GBL) intoxicated patients with a decreased Glasgow Coma Scale (GCS) score.

METHODS

This was a retrospective chart review of patients presenting to a Dutch tertiary urban ED with a reduced level of consciousness related to alleged GHB/GBL intoxication between April 2011-December 2014. Primary endpoint was major adverse events, defined by: upper airway obstruction not resolved with mayo tube or nasopharyngeal airway, hypoxia not resolved with 15 l of oxygen delivered via non-rebreathing mask, bradypnea not resolved after stimulation, intubation, bradycardia not resolved after intravenous atropine bolus, hypotension for which inotropes were started.

RESULTS

Data of 209 patients were retrieved. Major adverse events were reported in five patients (2.4%; 95% CI: 0.8-5.5). Intubation with subsequent ICU admission was required for 1.4% of patients (95% CI: 0.3-4.1). The most frequently seen minor adverse events (N = 209) were: airway obstruction (22%), hypothermia (14.8%), hypoxia (12.9%), bradycardia (8.1%), hypotension (6.7%), bradypnea (5.7%), vomiting (5.3%). There were no deaths. None of the patients had signs of aspiration pneumonia or returned to our ED due to complications.

CONCLUSION

Our study suggests that conservative airway management for patients with a decreased GCS due to suspected GHB intoxication may be safe. Major adverse events were present in 2.4% of patients, only 1.4% of patients required intubation. All minor adverse events were managed effectively with conservative treatment.

Unity in diversity: A systematic review on the GHB using population

BACKGROUND

Over the past decades gamma-hydroxybutyrate (GHB) has emerged as a popular drug with high potential of (ab)use due to its euphoric and relaxing effects. An overview of different populations using GHB is urgently needed, since this would enable development of adequate prevention and treatment policies to diminish the risks associated with GHB use. We systematically reviewed literature on different GHB using populations, comparing demographic characteristics, GHB use patterns, psychosocial aspects and psychiatric comorbidity.

METHODS

We conducted a systematic review following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines using Rayyan software. Original studies published from January 1997 up to October 2019 on GHB use were included. Out of 80 full-text articles, 60 articles of 51 unique studies were included. Most studies included people using GHB 1) presenting at emergency departments (n = 22), 2) recruited from the general population (n = 11), or 3) presenting at addiction care (n = 8).

RESULTS

Three main sub-populations of people using GHB are described in the literature: people using GHB recreationally without adverse effects; people using GHB recreationally with adverse effects, and people with dependence on GHB. These groups show considerable overlap in gender, age range, and comorbid substance use, as well as amount of GHB use per occasion. Differences are related to frequency and function of GHB use, the number of comas experienced, as well as work status, and psychiatric comorbidity.

CONCLUSION

Policy interventions should aim at preventing the transition from recreational substance use to GHB use, as most users are experienced recreational substance users prior to starting GHB use. When people use GHB regularly, interventions should aim at reducing the level of GHB use and preventing GHB use-related harm. Longitudinal studies and population-based probability sampling are required for more insight in the dynamics of GHB use in different sub-populations, and the transition from one group to the other, ultimately leading to dependence on GHB.

γ-Hydroxybutyric Acid (GHB) Pharmacokinetics and Pharmacodynamics: Semi-Mechanistic and Physiologically Relevant PK/PD Model

An overdose of γ-hydroxybutyric acid (GHB), a drug of abuse, results in fatality caused by severe respiratory depression. In this study, a semi-mechanistic pharmacokinetic/pharmacodynamic (PK/PD) model was developed to characterize monocarboxylate transporter 1 (MCT1)-mediated transport of GHB, as well as effects of GHB on respiration frequency, for IV doses of 200, 600, and 1500 mg/kg in rats. The proposed PK/PD model for GHB consists of nonlinear metabolism of GHB in the liver, MCT1-mediated renal reabsorption with physiologically relevant concurrent fluid reabsorption, MCT1-mediated uptake into the brain, and direct effects of binding of GHB to GABA_B receptors on the PD parameter, respiration frequency. Michaelis-Menten affinity constants for metabolism, renal reabsorption, and uptake into and efflux from the brain were fixed to the observed in vitro values. The IC ₅₀ value for the effect of GHB on respiration frequency was fixed to a reported value for binding of GHB to GABA_B receptors. All physiological parameters were fixed to the reported values for a 300-g rat. The model successfully captured the GHB PK/PD data and was further validated using the data for a 600-mg/kg dose of GHB after IV bolus administration. Unbound GHB brain ECF/blood partition coefficient (Kp _u,u ) values obtained from the model agreed well with values calculated using experimental ECF concentrations obtained with brain microdialysis, demonstrating the physiological relevance of this model. Sensitivity analysis indicated that the PK/PD model was stable. In conclusion, we developed a semi-mechanistic and physiologically relevant PK/PD model of GHB using in vitro drug-transporter kinetics and in vivo PK/PD data in rats.

Presentations to an urban emergency department in Switzerland due to acute γ-hydroxybutyrate toxicity

Background

γ-Hydroxybutyrate (GHB) is a drug of abuse with dose-dependent sedative effects. Systematic data on the acute toxicity of GHB from emergency department (ED) presentations over a long period of time are currently missing from the literature. The present study described the clinical features of GHB toxicity.

Methods

Retrospective case series of GHB intoxications seen in an urban ED.

Results

From January 2002 to September 2015, 78 GHB-related intoxication cases were recorded (71 % male patients). The mean ± SD age was 29 ± 8 years. The co-use of alcohol and/or other illicit drugs was reported in 65 % of the cases. Neurological symptoms other than central nervous system depression included agitation (40 %) and clonus (21 %). The most frequent reasons for admission were coma (64 %) and agitation (23 %). The median time to regain consciousness was 90 min (range, 3–400 min). Sudden recovery was reported in 25 cases (32 %). Coma was not significantly associated with polyintoxication. Coma occurred in 77 % of the alcohol co-users and in 62 % ofthe non-alcohol users (p=0.052). The mean recovery time in comatose patients was 142 min in patients with co-use of alcohol compared with 89 min in patients without alcohol co-use (p=0.07). Alcohol co-use was not significantly associated with nausea/vomiting (p=0.07). The co-use of stimulants was not significantly associated with non-responsive coma (Glasgow Coma Scale = 3) or mean recovery time. Analytical confirmation of GHB was available in 37 cases (47 %), with additional quantitative analysis in 20 cases. The median GHB concentration was 240 mg/L (range, 8.3–373 mg/L). Intoxication was severe in 72 % of the cases. No fatalities occurred, and 72 % of the patients were discharged directly home from the ED.

Discussion

There were trend associations between alcohol co-use and frequency and length of coma and nausea/vomiting which did not reach the significance level (all p=0.05-0.07) but may nevertheless be clinically relevant. As the exact time of use is not always known, and co-use of other substances can affect the severity of poisoning, no definitive conclusions can be drawn regarding the association between GHB concentration and severity.

Conclusion

Impaired consciousness and agitation were typical findings of GHB intoxication. The co-use of alcohol and/or other illicit substances is common but was not significantly associated with the severity of the intoxications in our study.

Semi-mechanistic kidney model incorporating physiologically-relevant fluid reabsorption and transporter-mediated renal reabsorption: pharmacokinetics of γ-hydroxybutyric acid and L-lactate in rats

This study developed a semi-mechanistic kidney model incorporating physiologically-relevant fluid reabsorption and transporter-mediated active reabsorption. The model was applied to data for the drug of abuse γ-hydroxybutyric acid (GHB), which exhibits monocarboxylate transporter (MCT1/SMCT1)-mediated renal reabsorption. The kidney model consists of various nephron segments--proximal tubules, Loop-of-Henle, distal tubules, and collecting ducts--where the segmental fluid flow rates, volumes, and sequential reabsorption were incorporated as functions of the glomerular filtration rate. The active renal reabsorption was modeled as vectorial transport across proximal tubule cells. In addition, the model included physiological blood, liver, and remainder compartments. The population pharmacokinetic modeling was performed using ADAPT5 for GHB blood concentration-time data and cumulative amount excreted unchanged into urine data (200-1000 mg/kg IV bolus doses) from rats [Felmlee et al (PMID: 20461486)]. Simulations assessed the effects of inhibition (R = [I]/KI = 0-100) of renal reabsorption on systemic exposure (AUC) and renal clearance of GHB. Visual predictive checks and other model diagnostic plots indicated that the model reasonably captured GHB concentrations. Simulations demonstrated that the inhibition of renal reabsorption significantly increased GHB renal clearance and decreased AUC. Model validation was performed using a separate dataset. Furthermore, our model successfully evaluated the pharmacokinetics of L-lactate using data obtained from Morse et al (PMID: 24854892). In conclusion, we developed a semi-mechanistic kidney model that can be used to evaluate transporter-mediated active renal reabsorption of drugs by the kidney.

Pattern and characteristics of ecstasy and related drug (ERD) presentations at two hospital emergency departments, Melbourne, Australia, 2008-2010

OBJECTIVE

To describe patterns and characteristics of emergency department (ED) presentations related to the use of ecstasy and related drugs (ERDs) in Melbourne, Australia.

METHODS

Retrospective audit of ERD-related presentations from 1 January 2008 to 31 December 2010 at two tertiary hospital EDs. Variation in presentations across years was tested using a two-tailed test for proportions. Univariate and multivariate logistic regressions were used to compare sociodemographic and clinical characteristics across groups.

RESULTS

Most of the 1347 presentations occurred on weekends, 24:00-06:00. Most patients arrived by ambulance (69%) from public places (42%), private residences (26%) and licensed venues (21%). Ecstasy-related presentations decreased from 26% of presentations in 2008 to 14% in 2009 (p<0.05); γ-hydroxybutyrate (GHB) presentations were most common overall. GHB presentations were commonly related to altered conscious state (89%); other presentations were due to psychological concerns or nausea/vomiting. Compared with GHB presentations, patients in ecstasy-related presentations were significantly less likely to require intubation (OR 0.04, 95% CI 0.01 to 0.18), but more likely to result in hospital admission (OR 1.77, 95% CI 1.08 to 2.91). Patients in amphetamine-related cases were older than those in GHB-related cases (median 28.4 years vs 23.9 years; p<0.05), and more likely to have a history of substance use (OR 4.85, 95% CI 3.50 to 6.74) or psychiatric illness (OR 6.64, 95% CI 4.47 to 9.87). Overall, the median length of stay was 3.0 h (IQR 1.8-4.8), with most (81%) patients discharged directly home.

CONCLUSIONS

Although the majority of ERD-related presentations were effectively treated, with discharge within a short time frame, the number and timing of presentations places a significant burden on EDs. ERD harm reduction and improved management of minor harms at licensed venues could reduce this burden.

γ-Hydroxybutyrate (GHB)-induced respiratory depression: combined receptor-transporter inhibition therapy for treatment in GHB overdose

Overdose of γ-hydroxybutyrate (GHB) frequently causes respiratory depression, occasionally resulting in death; however, little is known about the dose-response relationship or effects of potential overdose treatment strategies on GHB-induced respiratory depression. In these studies, the parameters of respiratory rate, tidal volume, and minute volume were measured using whole-body plethysmography in rats administered GHB. Intravenous doses of 200, 600, and 1500 mg/kg were administered to assess the dose-dependent effects of GHB on respiration. To determine the receptors involved in GHB-induced respiratory depression, a specific GABA(B) receptor antagonist, (2S)-(+)-5,5-dimethyl-2-morpholineacetic acid (SCH50911), and a specific GABA(A) receptor antagonist, bicuculline, were administered before GHB. The potential therapeutic strategies of receptor inhibition and monocarboxylate transporter (MCT) inhibition were assessed by inhibitor administration 5 min after GHB. The primary effect of GHB on respiration was a dose-dependent decrease in respiratory rate, accompanied by an increase in tidal volume, resulting in little change in minute volume. Pretreatment with 150 mg/kg SCH50911 completely prevented the decrease in respiratory rate, indicating agonism at GABA(B) receptors to be primarily responsible for GHB-induced respiratory depression. Administration of 50 mg/kg SCH50911 after GHB completely reversed the decrease in respiratory rate; lower doses had partial effects. Administration of the MCT inhibitor l-lactate increased GHB renal and total clearance, also improving respiratory rate. Administration of 5 mg/kg SCH50911 plus l-lactate further improved respiratory rate compared with the same dose of either agent alone, indicating that GABA(B) and MCT inhibitors, alone and in combination, represent potential treatment options for GHB-induced respiratory depression.

Reconsidering GHB: orphan drug or new model antidepressant?

For six decades, the principal mode of action of antidepressant drugs is the inhibition of monoamine re-uptake from the synaptic cleft. Tricyclic antidepressants, selective serotonin re-uptake inhibitors (SSRIs) and the new generation of dual antidepressants all exert their antidepressant effects by this mechanism. In the early days of the monoaminergic era, other efforts have been made to ameliorate the symptoms of depression by pharmacological means. The gamma-aminobutyric acid (GABA) system was and possibly still is one of the main alternative drug targets. Gammahydroxybutyrate (GHB) was developed as an orally active GABA analogue. It was tested in animal models of depression and human studies. The effects on sleep, agitation, anhedonia and depression were promising. However, the rise of benzodiazepines and tricyclic antidepressants brought GHB out of the scope of possible treatment alternatives. GHB is a GABA(B) and GHB receptor agonist with a unique spectrum of behavioural, neuroendocrine and sleep effects, and improves daytime sleepiness in various disorders such as narcolepsy, Parkinson's disease and fibromyalgia. Although it was banned from the US market at the end of the 1990s because of its abuse and overdose potential, it later was approved for the treatment of narcolepsy. New research methods and an extended view on other neurotransmitter systems as possible treatment targets of antidepressant treatment brought GHB back to the scene. This article discusses the unique neurobiological effects of GHB, its misuse potential and possible role as a model substance for the development of novel pharmacological treatment strategies in depressive disorders.

Acute toxicity and withdrawal syndromes related to γ-hydroxybutyrate (GHB) and its analogues γ-butyrolactone (GBL) and 1,4-butanediol (1,4-BD)

Gamma-hydroxybutyrate (GHB) has been used as a recreational drug since the 1990s and over the last few years there has been increasing use of its analogues gamma-butyrolactone (GBL) and to a lesser extent 1,4-butanediol (1,4BD). This review will summarize the literature on the pharmacology of these compounds; the patterns and management of acute toxicity associated with their use; and the clinical patterns of presentation and management of chronic dependency associated with GHB and its analogues.

Twenty-three deaths with gamma-hydroxybutyrate overdose in western Sweden between 2000 and 2007

BACKGROUND

gamma-Hydroxybutyrate (GHB) is a drug of abuse with a status as being safe. In spite of a reputation of low toxicity, a huge number of deaths associated with this drug have been recorded during recent years in Sweden. It is unclear whether coingestion with other drugs or ethanol causes death in GHB overdoses or whether GHB itself is the main cause of death.

OBJECTIVES

The aim of this study was to analyze the cause of death in GHB-related fatalities seen in our region.

METHODS

All cases of deaths with GHB during the year 2000-2007 in the region of western Sweden were studied retrospectively. The cases were classified as either GHB poisonings without any, with a minor or a major influence of other drugs on the cause of death.

RESULTS

Twenty-three cases were diagnosed as deaths due to GHB overdose. Ninety-one percent coingested other substances. Ninety-one percent of the decedents were male. Age varied between 16 and 46, with the median age at 25 years. Forty-three percent of the cases were classified as GHB poisonings without any or a minor influence of other drugs on the cause of death. Thirty percent also ingested ethanol. Two patients (9%) were only intoxicated with GHB.

CONCLUSIONS

Intoxication with GHB carries some mortality. Combining GHB with ethanol does not explain the many deaths in our region, nor do extremely high plasma concentrations of GHB. The intake of opioids increases the toxicity of GHB. The drug itself has such biological activities that an overdose is dangerous and may lead to death.

Forensic toxicology findings in deaths involving gamma-hydroxybutyrate

Concentrations of the illicit drug gamma-hydroxybutyrate (GHB) were determined in femoral venous blood and urine obtained at autopsy in a series of GHB-related deaths (N = 49). The analysis of GHB was done by gas chromatography after conversion to gamma-butyrolactone and quantitation of the latter with a flame ionization detector. The cutoff concentration of GHB in femoral blood or urine for reporting positive results was 30 mg/L. The deceased were mainly young men (86%) aged 26.5 +/- 7.2 years (mean +/- SD), and the women (14%) were about 5 years younger at 21.4 +/- 5.0 years. The mean, median, and highest concentrations of GHB in femoral blood (N = 37) were 294, 190, and 2,200 mg/L, respectively. The mean urine-to-blood ratio of GHB was 8.8, and the median was 5.2 (N = 28). In 12 cases, the concentrations of GHB in blood were negative (<30 mg/L) when the urine contained 350 mg/L on average (range 31-1,100 mg/L). Considerable poly-drug use was evident in these GHB-related deaths: ethanol (18 cases), amphetamine (12 cases), and various prescription medications (benzodizepines, opiates, and antidepressants) in other cases. Interpreting the concentrations of GHB in postmortem blood is complicated because of concomitant use of other psychoactive substances, variable degree of tolerance to centrally acting drugs, and the lack of reliable information about survival time after use of the drug.

Mimicking of Cerebral Herniation Through γ-Hydroxybutyric Acid Therapy

Besides being a treatment option for narcolepsy, γ-hydroxybutyrate is used as an adjuvant during anesthesia in Europe. In addition, it is illegally used as a recreational drug. Fixed and dilated, asymmetric pupils developed in 2 patients during continuous therapy with intravenous γ-hydroxybutyrate, which was added to the long-term anesthetics fentanyl and midazolam. Cerebral herniation as an alternative cause for the pupillary changes was ruled out by using continuous intracranial pressure monitoring and computed tomography. In both patients, the pupillary abnormalities resolved after discontinuation of γ-hydroxybutyrate. Thus, fixed and dilated pupils that are asymmetric seem to be an important side effect of γ-hydroxybutyrate therapy that may mimic cerebral herniation in deeply anesthetized patients.

Overview of the proton-coupled MCT (SLC16A) family of transporters: characterization, function and role in the transport of the drug of abuse gamma-hydroxybutyric acid

The transport of monocarboxylates, such as lactate and pyruvate, is mediated by the SLC16A family of proton-linked membrane transport proteins known as monocarboxylate transporters (MCTs). Fourteen MCT-related genes have been identified in mammals and of these seven MCTs have been functionally characterized. Despite their sequence homology, only MCT1-4 have been demonstrated to be proton-dependent transporters of monocarboxylic acids. MCT6, MCT8 and MCT10 have been demonstrated to transport diuretics, thyroid hormones and aromatic amino acids, respectively. MCT1-4 vary in their regulation, tissue distribution and substrate/inhibitor specificity with MCT1 being the most extensively characterized isoform. Emerging evidence suggests that in addition to endogenous substrates, MCTs are involved in the transport of pharmaceutical agents, including gamma-hydroxybuytrate (GHB), 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase inhibitors (statins), salicylic acid, and bumetanide. MCTs are expressed in a wide range of tissues including the liver, intestine, kidney and brain, and as such they have the potential to impact a number of processes contributing to the disposition of xenobiotic substrates. GHB has been extensively studied as a pharmaceutical substrate of MCTs; the renal clearance of GHB is dose-dependent with saturation of MCT-mediated reabsorption at high doses. Concomitant administration of GHB and L: -lactate to rats results in an approximately two-fold increase in GHB renal clearance suggesting that inhibition of MCT1-mediated reabsorption of GHB may be an effective strategy for increasing renal and total GHB elimination in overdose situations. Further studies are required to more clearly define the role of MCTs on drug disposition and the potential for MCT-mediated detoxification strategies in GHB overdose.

Gamma-hydroxybutyric acid (GHB) measurement by GC-MS in blood, urine and gastric contents, following an acute intoxication in Belgium

Gamma-hydroxybutyrate (GHB, sodium oxybate) is a compound related to neuromodulator gamma-aminobutyric acid (GABA), emerging as a recreational drug of abuse and as a rape drug. GHB-related emergencies have dramatically increased in the 1990s, but a decrease is observed since 2000. We describe the case of an acute GHB intoxication in a 28-year-old male who fell unconscious after ingestion of a mouthful of an unknown beverage, and required medical support for 2 days. A cocaine abuse was also detected by preliminary toxicological screening, but the clinical presentation was not typical of cocaine intoxication. A simple liquid-liquid extraction was used for quantitation of GHB, followed by disilyl-derivatization and analysis in selective ion monitoring (SIM) mode by gas chromatography-mass spectrometry (GC-MS), using GHB-d6 as internal standard. High concentrations of GHB were detected in urine (3020 mg/L) and gastric contents (71487 mg/L) at admission. After a 6-hours delay, GHB was still present in urine at 2324 mg/L and in blood at 43 mg/L. The clinical symptoms of cocaine intoxication were diminished by GHB consumption, and the cerebral scan was modified. Attention must thus be paid to acute intoxications with surprising clinical symptoms, and GHB has probably to be added to the preliminary toxicological screening. Data available regarding GHB are briefly reviewed, and our results are compared with previously published reports of non-fatal GHB intoxication.

Relative abuse liability of gamma-hydroxybutyric acid, flunitrazepam, and ethanol in club drug users

OBJECTIVES

Despite the increasing concern about gamma-hydroxybutyric acid (GHB) toxicity, there are few studies examining the clinical pharmacology of GHB and its abuse potential. To evaluate GHB-induced subjective and physiological effects, its relative abuse liability and its impact on psychomotor performance in club drug users.

MATERIALS AND METHODS

Twelve healthy male recreational users of GHB participated in 5 experimental sessions in the framework of a clinical trial. The study was randomized, double-blind, double-dummy, and crossover. Drug conditions were a single oral dose of GHB (40 or 60 mg/kg), ethanol (0.7 g/kg), flunitrazepam (1.25 mg), and placebo. Study variables included vital signs (blood pressure, heart rate, oral temperature, pupil diameter), psychomotor performance (digit symbol substitution test, balance, Maddox-Wing), subjective effects (a set of 13 visual analogue scales, Addiction Research Center Inventory-49 items, and Evaluation of the Subjective Effects of Substances with Potential of Abuse questionnaires), and pharmacokinetics.

RESULTS

All active conditions induced positive effects related to their abuse potential. The administration of GHB produced euphoria and pleasurable effects with slightly higher ratings than those observed for flunitrazepam and ethanol. Gamma-hydroxybutyric acid induced a biphasic time profile with an initial stimulant-like effect related to the simultaneous rise of plasma concentrations and a latter sedative effect not related to GHB kinetics. Gamma-hydroxybutyric acid increased blood pressure and pupil diameter. Ethanol induced its prototypical effects, and flunitrazepam produced marked sedation. Gamma-hydroxybutyric acid and flunitrazepam impaired psychomotor performance, digit symbol substitution test, and balance task, whereas ethanol, at the dose tested, induced only mild effects exclusively affecting the balance task.

CONCLUSIONS

Our results suggest a high abuse liability of GHB and flunitrazepam in club drug users.

GHB urine concentrations after single-dose administration in humans

Gamma-hydroxybutyric acid (GHB) is used as an illicit drug and is implicated in drug-facilitated sexual assault, but it also has some therapeutic uses. Detection of GHB in urine is important for forensic testing and could be of clinical benefit in overdose management. Urine GHB concentration-time profiles have not been well-characterized or correlated with doses used therapeutically. GHB levels were measured by gas chromatography-mass spectrometry in urine collected over 24 h from 16 adults administered single doses of 50 mg/kg GHB (Xyrem) alone and combined with 0.6 g/kg ethanol. Peak GHB urine concentrations averaged 150-200 mg/L and occurred in the 0-3 h urine collection. Significant variability in GHB urine levels between individuals was observed. Caucasians had lower urine concentrations than other races/ethnicities (p = 0.03). Men had lower GHB levels than women in the first 3 h after dosing (p = 0.038). Coingestion of ethanol did not significantly affect renal clearance of GHB, but urine GHB concentrations were lower in the first 3 h when ethanol and GHB were coingested (p = 0.039). At a proposed cut-off of 10 mg/L to distinguish endogenous versus exogenous GHB levels, 12.5% of the samples collected from 3 to 6 h, 81.3% of samples collected from 6 to 12 h, and 100% of urine specimens collected from 12 to 24 h were below this level. We conclude that the detection time for GHB in urine may be shorter than the previously reported 12-h window in some people taking therapeutic doses of GHB.

Experiences of gamma hydroxybutyrate (GHB) ingestion: a focus group study

GHB (gamma hydroxybutyrate) is a significant new drug of abuse added to the United States Controlled Substance Act in 2000. The majority of the published literature on GHB consists of clinical case reports, mainly from emergency departments, and a collection of laboratory-based studies, focused mainly on anesthesia. While comments about the various experiences and behaviors of human users are often included in such studies or reports, these aspects of GHB are only just beginning to be systematically investigated or detailed. Reported here are data from a qualitative study using focus group methods on the consumption habits, experiences, and beliefs of GHB users. A total of 51 people, 30 men and 21 women, mean age of 31.1+/-7.6 years (range 18 to 52 years), who report having used GHB for an average of 4.3+/-2.5 years (range one to 11 years), were interviewed in 10 separate groups held in 2004. This article discusses broadly the general experience of the GHB high, major perceived benefits including sexual responses to the drug, perceived risks and dangers of ingestion, co-ingestion, and various contexts of use. It concludes with a discussion of the implications drawn from this information for clinicians treating patients who use GHB.

Physostigmine for gamma-hydroxybutyrate coma: inefficacy, adverse events, and review

Physostigmine has been proposed as an antidote for gamma hydroxybutyrate (GHB) intoxication, based on associated awakenings in 1) patients anesthetized with GHB and 2) five of six patients administered physostigmine for GHB intoxication. However, there are neither well-supported mechanisms for physostigmine reversal of GHB effects, supportive animal studies, nor randomized, placebo-controlled trials demonstrating safety, efficacy, or improved outcomes. We sought to determine the outcomes of patients with GHB-induced coma after a physostigmine treatment protocol was instituted in an urban Emergency Department and ambulance service. Our search of medical records located five cases of GHB toxicity, all with co-intoxicants, who received physostigmine. None demonstrated response and, further, there were associated adverse events, including atrial fibrillation (2), pulmonary infiltrates (1) and significant bradycardia (1), and hypotension (1). We also reviewed 18 published GHB toxicity case series for incidence of adverse effects, stimulant co-intoxicants (which may heighten risk of physostigmine), complications, and outcomes of supportive care for GHB toxicity. We conclude that physostigmine is not indicated for reversal of GHB-induced alteration of consciousness; it is not efficacious, it may be unsafe, particularly in the setting of recreational polydrug use; and supportive care results in universally good outcomes.

Disposition of Gamma-Hydroxybutyric Acid in Conventional and Nonconventional Biologic Fluids After Single Drug Administration: Issues in Methodology and Drug Monitoring

Little controlled drug administration data are available to aid in the interpretation of gamma-hydroxybutyric acid (GHB) distribution in conventional and nonconventional fluids and the potential correlation between the pharmacokinetics of GHB and drug effects. Single oral sodium GHB doses of 50 mg/kg were administered to five volunteers. Plasma, oral fluid, urine, and sweat were analyzed for GHB by gas chromatography-mass spectrometry. GHB stability in plasma was studied at different storage temperatures. Subjective effects were measured using a set of 13 different visual analog scales. Mean peak GHB plasma concentrations at 30 minutes were 83.1 microg/mL. After the absorption phase, concentrations declined to mean values of 0.9 microg/mL at 6 hours. GHB was found in oral fluid at peak value concentrations equivalent to one third to one fourth of those found in plasma. The oral fluid-to-plasma ratio varied two fold in the 1- to 6-hour time range but always was lower than unit. The mean half-life (t1/2) of GHB was approximately 0.7 hour in plasma and approximately 1.2 hours in oral fluid. GHB urinary excretion is less than 2% of the dose administered. GHB was also detected in sweat at low concentrations. GHB showed a mixed sedative-stimulant pattern with subjective effects peaking between 1 and 1.5 hours after drug administration and lasting for 2 hours. Oral fluid and sweat appeared not to be suitable biologic matrices for monitoring GHB consumption. GHB-mediated subjective effects are related to GHB plasma concentrations.

Flavonoids modulate monocarboxylate transporter-1-mediated transport of gamma-hydroxybutyrate in vitro and in vivo

The objective of this study was to determine the effects of flavonoids on the in vitro monocarboxylate transporter 1 (MCT1)-mediated transport and in vivo disposition of the drug of abuse, gamma-hydroxybutyrate (GHB). The uptake of GHB in rat MCT1 gene-transfected MDA-MB231 cells was significantly decreased in the presence of the flavonoids apigenin, biochanin A, chrysin, diosemin, fisetin, genistein, hesperitin, kaempferol, luteolin, morin, narigenin, phloretin, and quercetin, but was not affected by the flavonoid glycosides phloridzin and rutin. The IC(50) values for luteolin, morin, and phloretin were 0.41 +/- 0.14, 6.41 +/- 2.01, and 2.57 +/- 0.48 microM, with the inhibition mechanism for luteolin being competitive. [(3)H]Kaempferol and [(3)H]biochanin A did not exhibit MCT1-mediated uptake, suggesting that these flavonoids are not substrates for MCT1. The combination of luteolin and phloretin inhibited the uptake of GHB in a synergistic manner; however, the combination of luteolin and morin was antagonistic. GHB 1000 mg/kg was administered to rats by i.v. bolus, with or without the concomitant administration of luteolin 10 mg/kg i.v. After luteolin treatment, the renal and total clearances of GHB were significantly increased, probably because of inhibition of the MCT1-mediated renal reabsorption of GHB, and the sleep time significantly decreased (121 +/- 5 min versus 165 +/- 10 min) compared with control rats. Overall, the results of this study indicate that flavonoids from food or herbal products may significantly alter the pharmacokinetics and pharmacodynamics of MCT substrates.

[Agitation and gamma-hydroxybutyrate]

Agitation is a symptom in various disorders. Gamma-hydroxybutyrate (GHB) is often abused because of its stimulating effects. Side effects comprise loss of consciousness, coma, and agitated states. We present a 50-year-old patient with repeated GHB intoxications and abstinent alcohol dependency and a video document showing an agitated state. Diagnostic workup is discussed considering the relevant literature on this topic. Intoxication and dependence on GHB are important entities in the contexts of neurology and psychiatry.

-Hydroxybutyrate (GHB) in Humans: Pharmacodynamics and Pharmacokinetics

Despite gamma-hydroxybutyrate (GHB) therapeutic uses and the increasing concern about its toxicity, few studies have addressed GHB dose-related effects under controlled administration and their relationship with its pharmacokinetics. The study design was double-blind, randomized, crossover, and controlled. As a pilot pharmacology phase I study, increasing doses of GHB were given. Single oral sodium GHB doses (40, 50, 60, and 72 mg/kg) were administered to eight volunteers. Plasma and urine were analyzed for GHB by gas chromatography-mass spectrometry. Physiological effects, psychomotor performance, and subjective effects were examined simultaneously. GHB produced dose-related changes in subjective effects as measured by questionnaires and VAS. GHB showed a mixed stimulant-sedative pattern, with initially increased scores in subjective feeling of euphoria, high, and liking followed by mild-moderate symptoms of sedation with impairment of performance and balance. Mean peak GHB plasma concentrations were 79.1, 83.1, 113.5, and 130.1 mug/L for 40, 50, 60, and 72 mg/kg, respectively. GHB-mediated physiological and subjective effects were dose dependent and related to GHB plasma concentrations. GHB urinary excretion was mainly related to administered doses. GHB-mediated subjective and physiological effects seem dose dependent and related to GHB plasma concentrations. Results suggest a high abuse liability of GHB in the range of dose usually consumed.

Transport of γ-Hydroxybutyrate in Rat Kidney Membrane Vesicles: Role of Monocarboxylate Transporters

Intoxication with gamma-hydroxybutyrate (GHB) is associated with coma, seizure, and death; treatment of overdoses is symptomatic. Previous studies in our laboratory have demonstrated that L-lactate and pyruvate treatment can increase the renal clearance of GHB and increase its elimination in rats, suggesting that GHB may undergo renal reabsorption mediated by monocarboxylic acid transporters (MCTs). The goals of this study were to characterize the renal transport of GHB in rats and to determine the role of MCT in its renal transport. Brush-border membrane (BBM) and basolateral membrane (BLM) vesicles were isolated from rat kidney cortex, and the uptake of L-lactate and GHB was characterized. L-Lactate and GHB undergo both pH- and sodium-dependent transport in BBM vesicles and pH-dependent transport in BLM vesicles. A simple Michaelis-Menten equation best described the pH-dependent uptake of GHB in BBM (Km, 8.0 +/- 1.8 mM; Vmax, 838 +/- 45 pmol/mg/s) and in BLM vesicles (Km, 10.5 +/- 2.6 mM; Vmax, 806 +/- 253 pmol/mg/s). mRNA of MCT1 and MCT2 was determined in rat kidney cortex using reverse transcriptase-polymerase chain reaction; using Western blot, the protein expression of MCT1 was present mainly in BLM vesicles, with weak expression in BBM vesicles, whereas that of MCT2 was exclusively in BLM vesicles. Studies with rat MCT1 gene-transfected MDA-MB231 cells demonstrated that GHB was a substrate of MCT1. The data suggest that rat MCT1 may represent an important transporter for GHB in renal tubule cells. This investigation provides evidence for the importance of MCTs in the reabsorption of the monocarboxylic acids l-lactate and GHB in the kidney.

Trends in gamma-hydroxybutyrate (GHB) and related drug intoxication: 1999 to 2003

STUDY OBJECTIVE

To analyze changes in gamma-hydroxybutyrate (GHB) case reporting, we review GHB or congener drug cases reported to the California Poison Control System, comparing these to other data sets.

METHODS

We identified cases from the California Poison Control System computerized database using standardized codes and key terms for GHB and congener drugs ("gamma butyrolactone," "1,4-butanediol," "gamma valerolactone"). We noted California Poison Control System date, caller and exposure site, patient age and sex, reported coingestions, and outcomes. We compared California Poison Control System data to case incidence from American Association of Poison Control Centers and Drug Abuse Warning Network data and drug use prevalence from National Institute for Drug Abuse survey data.

RESULTS

A total of 1,331 patients were included over the 5-year period (1999-2003). California Poison Control System-reported GHB exposures decreased by 76% from baseline (n=426) to the final study year (n=101). The absolute decrease was present across all case types, although there was a significant proportional decrease in routine drug abuse cases and an increase in malicious events, including GHB-facilitated sexual assault (P=.002). American Association of Poison Control Centers data showed a similar decrease from 2001 to 2003. Drug Abuse Warning Network incidence flattened from 2001 to 2002 and decreased sharply in 2003. National Institute for Drug Abuse survey time trends were inconsistent across age groups.

CONCLUSION

Based on the precipitous decrease in California Poison Control System case incidence for GHB during 5 years, the parallel trend in American Association of Poison Control Centers data, and a more recent decrease in Drug Abuse Warning Network cases, a true decrease in case incidence is likely. This could be due to decreased abuse rates or because fewer abusers seek emergency medical care. Case reporting may account for part of the decrease in the incidence of poison center contacts involving GHB.

Agitation is common in γ-hydroxybutyrate toxicity

Gamma-Hydroxybutyrate (GHB)-related compounds are most commonly described as depressants, with emphasis on somnolence, obtundation, stupor, and coma (SOSC). We sought to demonstrate the full spectrum of clinical presentations of GHB intoxication, including agitation and other nonsedative effects. Our observational study identified 66 patients with GHB toxicity, 40 of whom manifested agitation; 25 had agitation before or after SOSC, 10 had agitation alternating abruptly with SOSC, and 5 had agitation only. Fourteen presentations also included "bizarre" or self-injurious behaviors. Of 40 presentations with agitation, 19 had stimulant co-intoxicants confirmed by screen (14) or history (5). The remaining 21 patients with agitation were negative for stimulants by screen (12) or history (9). Gas chromatography/mass spectrometry detected GHB in 25 cases; 12 manifested agitation, 4 of which also screened negative for stimulants. Clinicians should broaden their definitions of GHB toxicity to include nonsedative effects such as agitation, combativeness, and bizarre or self-injurious behavior.

Site-dependent production of γ-hydroxybutyric acid in the early postmortem period

This study compared endogenous gamma-hydroxybutyric acid (GHB) concentrations in various postmortem fluid samples of 25 autopsy cases. All bodies were stored between 10-20 degrees C until autopsy, and the intervals between death and autopsy were less than 2 days (6-48 h). GHB concentrations were measured by headspace gas chromatography after GHB was converted to gamma-butyrolactone. Endogenous GHB concentrations were significantly higher in femoral venous blood (4.6+/-3.4 microg/ml, n=23) than in cerebrospinal fluid (1.8+/-1.5 microg/ml, n=9), vitreous humor (0.9+/-1.7 microg/ml, n=8), bile (1.0+/-1.1 microg/ml, n=9) and urine (0.6+/-1.2 microg/ml, n=12). GHB concentrations were similar in blood samples taken from different sites. Cut-off limits of 30 and 10 microg/ml are proposed for blood and urine, respectively, to discriminate between exogenous and endogenous GHB in decedents showing no or little putrefaction (postmortem intervals usually 48 h or less). The criterion established for endogenous GHB in postmortem urine may also be applicable to analytical results in cerebrospinal fluid, vitreous humor and bile from deceased persons.

Renal clearance of gamma-hydroxybutyric acid in rats: increasing renal elimination as a detoxification strategy

Intoxication with gamma-hydroxybutyric acid (GHB) is associated with coma, seizure, and death; treatment of overdoses is symptomatic. The objectives of this investigation were to characterize the renal clearance and total clearance of GHB in rats and to evaluate potential strategies for increasing the elimination of GHB after drug overdoses. GHB was administered by i.v. infusion at low (108 mg/h/kg), medium (128 mg/h/kg), or high (208 mg/h/kg) doses. Crossover studies were performed under steady-state conditions using the medium dose in the absence or presence of l-lactate, pyruvate, d-mannitol, sodium bicarbonate, or normal saline. GHB in plasma and urine samples was assayed using liquid chromatography-tandem mass spectrometry. Infusion of the low, medium, and high doses of GHB produced steady-state plasma concentrations of 0.22 +/- 0.04, 0.43 +/- 0.05, and 0.68 +/- 0.11 mg/ml. The renal clearance of the medium (51.8 +/- 13.0 ml/h/kg) and high (97.1 +/- 43.1 ml/h/kg) doses was significantly higher than that of the low dose (14.9 +/- 5.1 ml/h/kg), whereas the total clearance values were significantly lower than that of the low dose. The renal clearance was significantly increased by the concomitant administration of l-lactate, pyruvate, d-mannitol, or sodium bicarbonate with GHB but was not altered by normal saline. The total and metabolic clearance values were significantly increased by all treatments except normal saline. Overall, our results indicated that the renal clearance of GHB is dose-dependent, involving capacity-limited reabsorption. Monocarboxylate transport inhibitors, osmotic diuresis using d-mannitol, or the administration of sodium bicarbonate can increase the renal and total clearances of GHB. The approaches used in this investigation may offer potential detoxification strategies for the treatment of GHB overdoses.

A brief overview of the clinical pharmacology of "club drugs"

Four different "club drugs" are reviewed: MDMA (methylenedioxymethamphetamine, "Ecstasy"), GHB (gamma-hydroxybutyrate), ketamine, and Rohypnol (flunitrazepam). The neurobiology, clinical pharmacology, and treatment issues for each are discussed.

Fatalities associated with the use of γ‐hydroxybutyrate and its analogues in Australasia

OBJECTIVE

To identify deaths in Australasia associated with overdose of gamma-hydroxybutyrate (GHB) and its precursors (gamma-butyrolactone and 1,4-butanediol).

DESIGN

A retrospective search of medical and scientific information sources, as well as popular newsprint, for the period January 2000-August 2003, with formal clinical, toxicological and forensic evaluation of retrieved data.

MAIN OUTCOME MEASURE

Death associated with forensic data implicating GHB or its analogues.

RESULTS

Ten confirmed GHB-associated deaths were identified, with eight considered to be directly attributable to GHB. Only two of these eight cases were positive for ethanol toxicology.

CONCLUSIONS

Our study supports the existing evidence that GHB overdose is associated with fatalities, and that fatal overdoses occur in the context of isolated use.