GHB in postmortem toxicology. Discrimination between endogenous production from exposure using multiple specimens.

Area of Science:

• Forensic Toxicology
• Analytical Chemistry

Background:

• Gamma-hydroxybutyrate (GHB) is an endogenous compound found in blood and urine.
• Distinguishing endogenous GHB from exogenous exposure is crucial for toxicological assessments.
• Wide distribution of endogenous GHB necessitates cautious implementation of cut-off concentrations.

Purpose of the Study:

• To evaluate the accuracy of a proposed 50 mg/l postmortem blood cut-off for gamma-hydroxybutyrate (GHB).
• To investigate the utility of alternative biological specimens in discriminating postmortem GHB formation from exogenous exposure.

Main Methods:

• Analysis of 71 autopsy cases with excluded GHB exposure using gas chromatography-mass spectrometry (GC-MS).
• Testing of cardiac blood, femoral blood, bile, and vitreous humor for GHB concentrations.
• Method involved precipitation, derivatization with BSTFA/TMCS, and GC-MS analysis.

Main Results:

• All 71 cardiac blood specimens tested positive for GHB, with concentrations ranging from 0.4-409 mg/l.
• Fourteen cases exceeded the proposed 50 mg/l cut-off, attributed to postmortem formation.
• Bile was unsuitable for discrimination; femoral blood and vitreous humor showed potential for differentiating GHB levels.

Conclusions:

• A postmortem blood GHB concentration above 50 mg/l alone is insufficient to confirm drug exposure.
• Analysis of ancillary specimens, particularly vitreous humor and femoral blood, is essential for accurate toxicological interpretation.
• Careful consideration of endogenous GHB levels and postmortem changes is vital in forensic toxicology.