L. Tedeschi

Dose-dependent absorption and elimination of gamma-hydroxybutyric acid in healthy volunteers

SummaryGamma-hydroxybutyric acid (GHB) is effective in treatment of the alcohol and opiate withdrawal syndromes. Its absorption and disposition kinetics have been studied in 8 healthy male volunteers following oral administration of single doses of 12.5, 25 and 50 mg kg−1.The AUC increased disproportionately with the dose and so the apparent oral clearance decreased significantly as the dose was increased, whereas the terminal half-life and mean residence time increased. The peak plasma concentrations normalised to the lowest dose fell significantly with increasing doses, whilst the corresponding peak times increased.These findings suggest that both the oral absorption and the elimination of GHB are capacity-limited processes. GHB did not bind to significant extent to plasma proteins over the therapeutic concentration range.The pharmacokinetic parameters in healthy volunteers were not significantly different from those previously observed in alcohol-dependent patients with compensated alcoholic liver disease.

Fatality Due to Gamma-Hydroxybutyric Acid (GHB) and Heroin Intoxication

The first case of fatal intoxication due to ingestion of gamma-hydroxybutyric acid (GHB) and intravenous use of heroin is reported. A 42-year-old man, known to have been a heroin addict and to have taken other psychoactive substances, who had been in treatment with GHB for several months, was found dead. Anatomohistopathologic examination showed generalized visceral congestion, edema and pulmonary anthracosis, chronic bronchitis and chronic active hepatitis. Toxicological findings included fluid and tissue distributions of GHB, morphine and 6-monoacetylmorphine. GHB and morphine concentrations were respectively 11.5 and 0.77 micrograms/mL (blood), 84.3 and 0.3 micrograms/mL (vitreous humor), 258.3 and 1.35 micrograms/mL (urine), 57.0 and 14.3 micrograms/mL (bile), 40.0 and 0.43 micrograms/g (brain), 43.0 and 0.60 micrograms/g (liver), 47.0 and 0.68 micrograms/g (kidney). Blood and urine levels of 6-monoacetylmorphine were 28.5 and 12.1 ng/mL respectively. The presumed mechanism of action and pharmacokinetics of GHB are briefly reviewed, with reference to its therapeutic use and to reports of non-fatal GHB intoxication.

Therapeutic gamma-hydroxybutyric acid monitoring in plasma and urine by gas chromatography—mass spectrometry

A gas chromatographic-mass spectrometric (GC-MS) method for the determination of therapeutic levels of gamma-hydroxybutyric acid (GHB) in plasma and urine samples is described. GHB is converted to its lactonic form gamma-butyrolactone (GBL) which is extracted from biological fluids after the addition of the internal standard delta-valerolactone. Final GC-MS analysis is obtained under electron impact selected ion monitoring (SIM) conditions. Mean relative recoveries of GHB from plasma and urine are 75.5% (RSD% = 2.2) and 76.4% (RSD% = 2.4), respectively. The assay is linear over a plasma GHB range of 2-200 micrograms ml-1 (r = 0.999) and a urine GHB range of 2-150 micrograms ml-1 (r = 0.998). Intra- and inter-assay relative standard deviations (n = 5) determined at 10 and 100 micrograms ml-1 are below 5%. The method is simple, specific and accurate, and may be applied for analytical purposes related to pharmacokinetic studies and therapeutic drug monitoring.

Detection of thiopental and pentobarbital in head and pubic hair in a case of drug-facilitated sexual assault.

The quali-quantitative determination of two barbiturates, thiopental and its metabolite pentobarbital, in head and pubic hair samples of a woman who had been sexually assaulted during hospitalisation, is reported. Hair was analysed by means of solid-phase microextraction (SPME) and gas chromatography-multiple mass spectrometry (GC-MS-MS), in chemical ionisation conditions. Thiopental and pentobarbital were found in three proximal head hair segments (sample 1A: 0.30 and 0.40 ng/mg; sample 1B: 0.20 and 0.20 ng/mg; sample 3: 0.15 and 0.20 ng/mg) and pubic hair sample. Two distal head hair segments were negative for both barbiturates. Despite the lack of collection and toxicological analysis of blood or urine samples within the hospital setting, analytical findings from hair revealed the use of the anaesthetic agent thiopental to sedate the victim quickly and deeply and commit sexual assault.

Determination of γ‐hydroxybutyric acid (GHB) in plasma and urine by headspace solid‐phase microextraction and gas chromatography/positive ion chemical ionization mass spectrometry

A new method for the qualitative and quantitative analysis of γ-hydroxybutyric acid (GHB) in plasma and urine samples is described. It involves the conversion of GHB to γ-butyrolactone (GBL), its subsequent headspace solid-phase microextraction (SPME), and detection by gas chromatography/positive ion chemical ionization mass spectrometry (GC/PICI-MS), using D6-GBL as internal standard. The assay is linear over a plasma GHB range of 1–100 µg/mL (n = 5, r = 0.999) and a urine GHB range of 5–150 µg/mL (n = 5, r = 0.998). Relative intra- and inter-assay standard deviations, determined for plasma and urine samples at 5 and 50 µg/mL, are all below 5%. The method is simple, specific and reasonably fast. It may be applied for clinical and forensic toxicology as well as for purposes of therapeutic drug monitoring. Copyright

Effect of moderate or severe liver dysfunction on the pharmacokinetics of γ-hydroxybutyric acid

Objectives: To assess the effect of moderate or severe liver dysfunction on the pharmacokinetics of γ-hydroxybutyric acid (GHB).Methods: The absorption and disposition kinetics of GHB were studied in eight cirrhotic patients without ascites (Child’s class A) and eight cirrhotic patients with ascites (Child’s class C), after administration of a single oral dose of 25 mg⋅kg−1. The liver metabolic function of each patient was evaluated by measuring antipyrine clearance and the formation rate of the lidocaine metabolite monoethylglycinexylidide (MEGX).Results:Compared to those previously determined in eight healthy control subjects given the same GHB dose, mean AUC values were double or greater in the cirrhotic patients. Accordingly, apparent oral clearance was markedly reduced (from 9.1 to 4.5 and 4.1 ml⋅min−1⋅kg−1 in nonascitic and ascitic patients, respectively). Terminal half-life (t1/2), was significantly longer in nonascitic patients than in control subjects (32 vs 22 min). A further significant prolongation of t1/2, most likely due to an increased distribution volume, was observed in patients with ascites (56 min). Nonetheless, GHB plasma concentrations fell to either undetectable or negligible levels by the end of the usual dosing intervals (6–8 h).More limited changes were noted in the absorption parameters. The peak level (Cmax) increased only in nonascitic patients, but not proportionally to the increase in AUC. The time to Cmax increased from 30 to 45 min in both cirrhotic groups. These findings are consistent with a slowed rate of GHB absorption in cirrhotic patients. Adverse effects were similar, for intensity and duration, to those recorded in healthy volunteers, i.e., mild and transient.Conclusions:Although liver cirrhosis causes significant modifications of GHB disposition kinetics, the increase in t1/2 is not such as to cause drug accumulation on repetitive dosing. However, in consideration of the higher mean plasma levels observed in cirrhotic patients, it appears wise to keep the initial GHB daily dose at the lower end of the therapeutic range and to carefully monitor the patients if upward dose adjustments are required.

Simultaneous identification of amphetamine and its derivatives in urine using HPLC-UV

SummaryAn HPLC-UV method for the simultaneous identification of amphetamine, methamphetamine, 3,4-methylenedioxyamphetamine (MDA) and 3,4-methylenedioxymethamphetamine (MDMA) in urine is described. It includes a rapid extraction procedure of the 4 analogs from urine using Extrelut 3 columns, derivatization with sodium 1,2-naphthoquinone-4-sulphonate (NQS) to obtain highly chromophoric UV-VIS derivatives, and a final HPLC analysis using an ion-pair reversed-phase technique with eluent monitoring at 480 nm. Structural characterization of the derivatives obtained by mass spectrometry is reported. Recoveries of the amphetamines were in the range 80–85% at concentrations of 300 ng/ml. Practical detection limits were 40–60 ng/ml (S/N ratio = 10) for all derivatives. The chromatographic peaks of the NQS derivatized amphetamines are fairly narrow and well resolved. The method is simple, rapid, quite sensitive, and specific for convenient confirmation of preliminary positive results obtained with immunoassays.ZusammenfassungEine HPLC-UV-Methode zur gleichzeitigen Bestimmung von Amphetamin, Methamphetamin, 3,4-Methylendioxyamphetamin (MDA) und 3,4-Methylendioxymethamphetamin (MDMA) im Urin wird beschrieben. Vorgestellt wird eine Schnellextraktion der 4 Amphetamine über Extrelut-3-Säulen und eine Derivatisierung mit Natrium-1,2-naphthochinon-4-sulfonat (NQS) um hochchromophore UV-VIS-Derivate zu erhalten. Abschließend erfolgt eine HPLC-Analyse mittels einer reversed phase Technik (Ionenpaar) mit Detektion des Eluats bei 480 nm. Die Struktur der NQS-Derivate wird durch Massenspektrometrie charakterisiert. Die Wiederfindungsraten der Amphetamine liegen bei Konzentrationen von 300 ng/ml bei 80–85%. Die Nachweisgrenze liegt für alle Derivate bei 40–60 ng/ml (S/N-Verhältnis = 10). Die Trennung der NQS-derivatisierten Amphetamine gelingt gut, die Methode ist einfach, schnell, empfindlich und spezifisch genug für die Bestätigung vorläufiger Screening-Resultate, wie sie mit Hilfe von Immunoassays erhalten werden.

Endogenous γ-hydroxybutyric acid is in the rat, mouse and human gastrointestinal tract

Abstract By using Gas Chromatography-Mass Spectrometry high concentrations of endogenous γ-hydroxybutyric acid (GHB) have been demonstrated in the rat and mouse gastrointestinal tract, including stomach, small intestine and colon–rectum. GHB concentrations were many folds higher than those present in the brain. High GHB concentrations have been also found in the human operatory specimen of sigmoid colon. Since GHB administration has been found to modify gastrointestinal motility via GABA B receptors, the present results suggest that endogenous GHB might be involved in the GABA B receptor-mediated control of gastrointestinal function.

Concentrations of Phenobarbital, Flurazepam, and Flurazepam Metabolites in Autopsy Cases

In five cases of death resulting from acute intoxication with phenobarbital and flurazepam, the blood, urine, brain, lung, liver, and kidney levels of these drugs as well as the levels of N-1 hydroxyethyl, N-1 desalkyl, and N-1 desalkyl-3-hydroxy flurazepam metabolites were determined. Concentration of flurazepam and its metabolites was determined by using new gas chromatographic conditions employing a selective detector for nitrogen-containing substances and a column of 1% SP-1000. In addition, the EMIT technique was also employed on blood and urine samples and the results compared with GLC data.

Comparison of GLC-EMIT analysis for the assay of methadone and its major metabolite in urine

The enzyme-multiplied immunoassay technique (EMIT) was compared with the gas-liquid chromatographic (GLC) method in the analysis of 130 urine samples from subjects receiving methadone treatment and non-methadone controls. The GC method allowed the quantitation of 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine, and major metabolite of methadone. A good correlation was found between the two methods. The advantages of using the EMIT system are discussed.