Delta-8 Tetrahydrocannabinol and Driving Under The Influence:
Over the past three years, there has been a marked increase in interest in cannabinoid products, particularly those containing Delta-8 Tetrahydrocannabinol (THC). This rise in popularity has ignited debates over its legal status.
Delta-8 THC is an isomer of delta-9 THC, which serves as the primary psychoactive component in Cannabis sativa. Delta-8 THC also reportedly possesses about 60% of delta-9 THC’s psychoactive strength.
It also has a similar binding affinity to cannabinoid receptors CB1 and CB2, which makes it a substance of forensic concern.
Toxicology laboratories increasingly find themselves receiving requests to detect and quantify delta-8 THC in blood samples in cases of driving under the influence of drugs (DUID). However, many laboratories face challenges in differentiating and identifying THC isomers, leading to complications in reporting. The precise range of delta-8 THC concentrations in forensic cases is largely unknown.
The laboratory in question conducts tests for cannabinoids in human blood using liquid chromatography with tandem mass spectrometry (LC-MS-MS). Although the laboratory can separate delta-8 and delta-9 THC isomers, it does not report delta-8 THC levels in routine DUID toxicology tests because it lacked a specific internal standard when developers created the test in 2019.
The Study:
Recently, the laboratory undertook a study involving 118 randomly selected blood samples from forensic cases to estimate typical delta-8 THC concentrations. The objective of this study was to develop a method for routinely quantifying both delta-8 and delta-9 THC levels.
The laboratory calculated delta-8 THC concentrations by applying a correction factor for the relative molar response of each isomer on its LC-MS-MS system. Researchers derived this factor from validation experiments for a quantitative delta-9 THC method that achieved baseline separation of the isomers.
Results:
The original validation in 2019 adhered to standards from the Academy Standards Board and the National Institute for Standards and Testing, attempting to quantify delta-8 THC using delta-9 THC-d3 as an internal standard.
The validation showed that processing samples within 12 hours made quantifying delta-8 THC achievable. However, beyond this timeframe, the method did not meet the standard for delta-8 THC analysis due to significant matrix effects. The laboratory hypothesised that the differential rates of adsorption of the isomers to autosampler vials might explain this limitation.
In the assessment for research purposes, the laboratory reviewed validation data for delta-9 and delta-8 THC standards, demonstrating that the absolute peak area of delta-8 THC was consistently about 25% less than that of delta-9 THC at equivalent concentration levels.
Researchers derived an average correction factor of 1.34 to account for this difference, enabling them to accurately measure delta-8 THC concentrations in a series of human whole blood samples from suspected human performance toxicology cases.
Analysing 118 randomly selected cases, where delta-8 THC was identified, revealed the mean concentrations of delta-8 THC and delta-9 THC.
Approximately 90% of the delta-8 THC concentrations were found to be below 8.0 ng/mL.
In the majority of cases, both delta-8 and delta-9 THC were present above the assay’s reporting limit of 0.5 ng/mL. For 70% of these cases, the concentration of delta-9 THC was higher than that of delta-8 THC by an average factor of 5.7.
In six cases, the analysis detected only delta-8 THC, with concentrations ranging between 1.7 and 6.2 ng/mL.
