Cannabinoid Stability in Antemortem and Postmortem Blood.

In toxicological testing, drug stability is important when providing quantitative results and interpretation of findings, as well as when collecting correlation data. The goal of this study was to expand on previous stability studies and to evaluate other cannabinoids encountered in forensic toxicology. In this 6-month study, the stability of Δ-9-tetrahydrocannabinol (THC), 11-hydroxy-THC, 11-nor-9-carboxy-THC, Cannabinol and Cannabidiol in antemortem and postmortem blood was evaluated in refrigerated (4°C) and frozen (-4°C) storage conditions. Pooled antemortem and postmortem bloods were fortified at low and high concentrations and stored in untreated glassware. Over 6 months, samples were analyzed by automated extraction and liquid chromatography-mass spectrometry/mass spectrometry to evaluate the change in concentration over time. Samples in each storage condition were analyzed in triplicate 12 times over the 6-month period. Cannabinoids in antemortem blood were more stable in the refrigerated condition than in the frozen condition, with 11-hydroxy-THC, 11-nor-9-carboxy-THC and Cannabinol having more than 80% of the original concentration remaining at the end of the study. Cannabinoids in postmortem blood had improved stability in the frozen storage condition with THC, 11-hydroxy-THC, 11-nor-9-carboxy-THC and Cannabinol in the low concentration pool with more than 80% of the original concentration remaining. These data demonstrated that cannabinoids may decrease in concentration over time when stored in untreated glass vials. To ensure the most accurate determination of drug concentration, samples containing cannabinoids should be analyzed as soon as possible.