Pharmacokinetic properties of γ-Hydroxybutyrate (GHB) in whole blood, serum, and urine

Over the last 10–15 years, g-hydroxybutyrate (GHB) and gbutyrolactone have become increasingly popular 'club drugs', but they have also gained attention as potential agents of drug-facilitated sexual assault (DFSA). Several studies have attempted to characterize GHB’s pharmacokinetic properties in humans, and the aim of this paper is to build on this research with an emphasis on DFSA cases. A 25 mg/kg dose of GHB was given to 12 GHB-naïve volunteers (6 men and 6 women). Urine and blood samples (serum and whole blood) were collected and analyzed by gas chromatography–mass spectrometry following liquid–liquid extraction. The urinary Tmax was 1 h in 11 volunteers with a mean Cmax of 67.6 mg/L (32.6–161.3 mg/L). Urinary concentrations rapidly decreased to < 10 mg/L (interpretive limit) for 11 volunteers after just 4 h. Data derived from whole blood (mean Cmax 5 48.0 mg/L, Tmax 5 24.6 min) closely matched that from serum (mean Cmax 5 59.4 mg/L, Tmax 5 23.3 min), suggesting GHB is distributed into erythrocytes. All 12 volunteers had GHB concentrations of less than 5 mg/L in both whole blood and serum after 3 h. Results verify the rapid elimination of GHB and the limited retrospective power of a concentration-based approach to prove GHB administration in blood and urine and confirm that, in DFSA cases, samples should be collected as soon as possible.