Pharmacokinetics and excretion of gamma-hydroxybutyrate (GHB) in healthy subjects

In Europe and the United States, the recreational use of gammahydroxy butyric acid (GHB) at dance clubs and 'rave' parties has increased substantially. In addition, GHB is used to assist in the commission of sexual assaults. The aim of this controlled clinical study was to acquire pharmacokinetic profiles, detection times, and excretion rates in human subjects. Eight GHB-naïve volunteers were administered a single 25-mg/kg body weight oral dose of GHB, and plasma, urine, and oral fluid specimens were analyzed by using gas chromatography-mass spectrometry (GC-MS). Liquid-liquid extraction was performed after acid conversion of GHB to gamma-butyrolactone. Limits of quantitation of 0.1 (oral fluid), 0.2 (urine), and 0.5 µg/mL (plasma) could be achieved in the selected ion monitoring mode. GHB plasma peaks of 39.4 ± 25.2 µg/mL (mean ± SEM) occurred 20–45 min after administration. The terminal plasma elimination half-life was 30.4 ± 2.45 min, the distribution volume 52.7 ± 15.0 L, and the total clearance 1228 ± 233 µL/min. In oral fluid, GHB could be detected up to 360 min, with peak concentrations of 203 ± 92.4 µg/mL in the 10-min samples. In urine, 200 ± 71.8 and 230 ± 86.3 µg/mL, were the highest GHB levels measured at 30 and 60 min, respectively. Only 1.2 ± 0.2% of the dose was excreted, resulting in a detection window of 720 min. Common side-effects were confusion, sleepiness, and dizziness; euphoria and change of vital functions were not observed. GHB is extensively metabolized and rapidly eliminated in urine and oral fluid. Consequently, samples should be collected as soon as possible after ingestion.