Phencyclidine and cannabinoids in vitreous humor

Area of Science:

• Forensic Toxicology
• Postmortem Analysis
• Analytical Chemistry

Background:

• Vitreous humor (VH) is commonly collected during autopsies.
• Recent advancements allow for drug of abuse testing in VH.
• This study investigates VH's utility for detecting specific drugs.

Purpose of the Study:

• To evaluate the effectiveness of vitreous humor for detecting phencyclidine (PCP) and cannabinoids.
• To compare drug concentrations in VH with blood.
• To identify potential challenges in VH drug analysis.

Main Methods:

• Assayed 30 VH samples for phencyclidine (PCP) and 50 for cannabinoids.
• Screened specimens using immunoassay.
• Confirmed positive results with Gas Chromatography-Flame Ionization Detection (GC-FID) for PCP and Gas Chromatography-Mass Spectrometry (GC/MS) for cannabinoids.

Main Results:

• 60% of VH specimens screened positive for PCP (cutoff 25 ng/mL).
• PCP concentrations in positive VH samples ranged from 30-290 ng/mL (blood: 50-600 ng/mL).
• All VH specimens screened negative for cannabinoids; however, GC/MS detected one positive case for 11-nor-9-carboxy-delta-9-tetrahydrocannabinol at 2 ng/mL, suggesting potential matrix effects causing false negatives.

Conclusions:

• Vitreous humor shows promise as a reliable specimen for detecting phencyclidine (PCP).
• Vitreous humor may not be suitable for routine cannabinoid detection due to potential false negatives.
• Further research is needed to understand matrix effects in VH drug analysis.