Stability of ecgonine methyl ester in postmortem urine specimens

Area of Science:

• Forensic Toxicology
• Analytical Chemistry
• Pharmacology

Background:

• Cocaine use is a significant public health concern.
• Accurate detection of cocaine and its metabolites is crucial for forensic investigations.
• Ecogonine methyl ester (EME) is a primary metabolite of cocaine.

Purpose of the Study:

• To evaluate the stability of ecogonine methyl ester (EME) in postmortem urine specimens.
• To determine the impact of refrigerated (4°C) and frozen (-20°C) storage conditions on EME stability over six months.
• To assess the utility of EME as a biomarker for in vivo cocaine use.

Main Methods:

• Analysis of 25 postmortem urine specimens positive for cocaine and EME.
• Gas chromatography/mass spectrometry (GC/MS) for quantitation of cocaine and EME.
• Specimen storage at 4°C and -20°C with testing at multiple intervals over six months.

Main Results:

• EME concentrations remained stable within 20% of initial values in 22/25 frozen specimens and 19/25 refrigerated specimens after six months.
• At least 50% of initial EME was detected in all specimens under both storage conditions.
• Cocaine concentrations decreased over time, while EME concentrations did not increase, suggesting in vivo conversion.

Conclusions:

• EME is a stable metabolite in postmortem urine under both refrigerated and frozen storage conditions for up to six months.
• The stability and lack of post-collection increase support EME as a reliable indicator of in vivo cocaine metabolism and use.
• These findings enhance the reliability of EME detection in forensic toxicology, particularly in postmortem cases.