A study of urinary endogenous gamma-hydroxybutyrate (GHB) levels

Area of Science:

• Forensic Toxicology
• Analytical Chemistry
• Human Physiology

Background:

• Recreational use of gamma-hydroxybutyrate (GHB) necessitates its detection in forensic toxicology.
• Differentiating endogenous GHB from exogenous sources is a significant analytical challenge.
• Establishing reliable reference ranges for endogenous GHB is crucial for accurate interpretation of forensic samples.

Purpose of the Study:

• To determine typical urinary endogenous levels of GHB in a diverse human population.
• To provide a scientific basis for differentiating recreational GHB use from natural physiological levels.
• To validate a proposed cutoff concentration for routine forensic screening of GHB.

Main Methods:

• Analysis of urine samples from 55 human subjects (ages 6-59).
• Initial screening using a hydrolysis method converting GHB to gamma-butyrolactone (GBL), followed by GC-MS analysis.
• Confirmation testing via solid-phase extraction, derivatization to GHB di-TMS, and GC-MS analysis.

Main Results:

• The median endogenous urinary GHB concentration was 1.3 µg/mL (mean = 1.65 µg/mL, range 0.9-3.5 µg/mL).
• The standard deviation was 0.68 µg/mL, indicating a relatively tight distribution of endogenous levels.
• These findings support the previously suggested cutoff of 10 µg/mL for forensic analysis.

Conclusions:

• The established endogenous GHB levels provide a critical reference for forensic toxicologists.
• The 10 µg/mL cutoff concentration is confirmed as effective for distinguishing recreational GHB use.
• This research enhances the accuracy and reliability of GHB testing in forensic casework.