Endogenous GHB in Segmented Hair Part I: Inter-individual Variation for Group Comparisons

Area of Science:

• Forensic Toxicology
• Analytical Chemistry
• Pharmacology

Background:

• Interpreting gamma-hydroxybutyric acid (GHB) in hair is challenging due to its endogenous presence.
• Previous studies lacked sufficient sample sizes to establish reliable endogenous GHB baselines.
• Understanding endogenous GHB variation is crucial for accurate interpretation of exogenous GHB.

Purpose of the Study:

• To evaluate the inter-individual variation of endogenous GHB concentrations in human hair.
• To establish baseline endogenous GHB levels using a large-scale hair sample analysis.
• To investigate sex-based differences in endogenous GHB hair concentrations and trends.

Main Methods:

• Analysis of over 2,000 hair segments (3-12 cm) from 141 women and 73 men.
• Application of imputation methods assuming lognormal distribution to include non-detect data.
• Kruskal-Wallis tests for group comparisons of segmental GHB concentrations.

Main Results:

• The estimated endogenous GHB range in hair was 0.16-5.47 ng/mg, with 97.5% below 2.00 ng/mg.
• Significant differences in median GHB concentrations were found between male and female hair segments.
• Distinct proximal-to-distal concentration trends observed: decreasing in females, increasing in males.

Conclusions:

• This study provides the largest dataset to date on endogenous GHB concentrations in hair.
• Significant sex-based differences in GHB hair concentrations and chronological trends were identified.
• The findings offer crucial data for improving the interpretation of GHB in forensic hair analysis.