Time-Dependent Changes in THC Concentrations in Deceased Persons

Quantitative analysis of tetrahydrocannabinol isomers and other toxicologically relevant drugs in blood

A multi-analyte liquid chromatography-tandem mass spectrometry (LC-MS/MS) method is described, involving the separation of delta-9-tetrahydrocannabinol (delta-9-THC) and delta-8-THC in addition to other commonly encountered drugs and metabolites. Briefly, sample preparation involved an alkaline liquid-liquid extraction (methyl tert-butyl ether) of blood (100 μl). The solvent layer was transferred, evaporated to dryness, reconstituted, and samples then separated on an Agilent Poroshell 120 EC-C18 100 Å (50 mm × 3.0 mm, 2.7 μm) analytical column using a multi-step gradient elution of 50 mM ammonium formate in water (pH 3.5) and 0.1% formic acid in methanol over 14 min. A SCIEX Triple Quad 6500+ system operating in scheduled multiple reaction monitoring and positive electrospray ionization was used for detection. There were no interferences, and matrix effects were generally acceptable (±20% of neat response). Linearity was achieved within the calibration range, including methylamphetamine (MA) (10-1000 ng/ml), 3,4-methylenedioxy-N-methylamphetamine (MDMA) (10-1,000 ng/ml), cocaine (10-1000 ng/ml), and two THC isomers (1-100 ng/ml). Accuracies of MA, MDMA, cocaine, and two THC isomers were 3.6 to 8.9%, -1.2 to 4%, -5.3 to 5.8%, and -11 to 14%, respectively; while precision estimates of the same were 1.6 to 5.4%, 1.7 to 5.3%, 1.2 to 4.5%, and 2 to 10%, respectively. Autosampler stability and dilution integrity were within acceptable limits, and no carryover was detected at the limit of detection. This validated LC-MS/MS method made the routine identification of both delta-9-THC and delta-8-THC in blood possible.

Difficulties associated with the interpretation of postmortem toxicology

While postmortem (PM) toxicology results provide valuable information towards ascertaining both the cause and manner of death in coronial cases, there are also significant difficulties associated with the interpretation of PM drug levels. Such difficulties are influenced by several pharmacokinetic and pharmacodynamic factors including PM redistribution, diffusion, site-to-site variability in drug levels, different drug properties and metabolism, bacterial activity, genetic polymorphisms, tolerance, resuscitation efforts, underlying conditions, and the toxicity profile of cases (i.e. single- or mixed-drug toxicity). A large body of research has been dedicated for better understanding and even quantifying the influence of these factors on PM drug levels. For example, several investigative matrices have been developed as potential indicators of PM redistribution, but they have limited practical value. Reference tables of clinically relevant therapeutic, toxic, and potentially fatal drug concentrations have also been compiled, but these unfortunately do not provide reliable reference values for PM toxicology. More recent research has focused on developing databases of peripheral PM drug levels for a variety of case-types to increase transferability to real-life cases and improve interpretations. Changes to drug levels after death are inevitable and unavoidable. As such, guidelines and practices will continue to evolve as we further our understanding of such phenomena.

Time- and temperature-dependent postmortem ∆9-tetrahydrocannabinol concentration changes in rabbits following controlled inhaled cannabis administration

ostmortem redistribution (PMR), a well-known phenomenon in forensic toxicology, can result in substantial changes in drug concentrations after death, depending on the chemical characteristics of the drug, blood collection site, storage conditions of the body and postmortem interval (PMI). Limited PMR data are available for ∆9-tetrahydrocannabinol (THC), the primary psychoactive component in Cannabis sativa. PMR was evaluated after controlled cannabis inhalation via a smoking machine and exposure chamber in New Zealand white rabbits. Necropsies were performed on five control rabbits immediately after euthanasia, whereas 27 others were stored at room temperature (21°C) or refrigerated conditions (4°C) until necropsy at 2, 6, 16, 24 or 36 h after death. THC and its Phase I and glucuronidated Phase II metabolites were quantified in blood, vitreous humor, urine, bile and tissues by liquid chromatography-tandem mass spectrometry (LC-MS-MS). Under refrigerated temperature, heart blood THC concentrations significantly increased at PMI 2 h in rabbits, whereas peripheral blood THC concentrations showed a significant increase at PMI 16 h. Central:peripheral blood and liver:peripheral blood ratios for THC ranged from 0.13 to 4.1 and 0.28 to 8.9, respectively. Lung revealed the highest THC concentrations, while brain and liver exhibited the most stable THC concentrations over time. This report contributes much needed data to our understanding of postmortem THC behavior and can aid toxicologists in the interpretation of THC concentrations in medicolegal death investigations.

Postmortem redistribution of cannabinoids: Statistical analysis of a novel dataset and meta-analysis

The assessment of human postmortem concentrations of Δ9-THC (THC) and its metabolites, 11-nor-9-carboxy-THC (THCCOOH) and 11-hydroxy-THC (11-OH-THC), is routinely performed in forensic toxicology laboratories. However, the literature on cannabinoids postmortem redistribution (PMR) is scarce and highlights their complex postmortem changes. This study aims to investigate the postmortem behavior of THC and its metabolites in order to provide practitioners with potential indicators of PMR. To do so, antemortem and postmortem cases positive for cannabinoids were compiled in a database. Its analysis shows significantly higher THC concentrations in postmortem blood than in antemortem blood. Antemortem and postmortem blood also present significantly different profiles for their THC to THCCOOH ratios. Whereas antemortem blood generally shows THCCOOH concentrations higher or equal to THC, several postmortem cases show the opposite, with THC concentrations higher than THCCOOH. While occurrence of postmortem redistribution (PMR) is difficult to measure directly, an evaluation was performed using the central to peripheral (C/P) blood concentrations ratio as a proxy. With a C/P significantly lower than 1.0 for THC and significantly higher than 1.0 for THCCOOH, the PMR hypothesis is supported for both compounds, with redistribution towards peripheral blood for THC and towards central blood for THCCOOH. On the other hand, 11-OH-THC does not show a C/P significantly different than 1.0, suggesting the absence of PMR. Influence of body mass index, conservation state and postmortem interval on C/P was statistically analyzed and no significant impact was observed. To compare and contrast C/P observed in the database with those published in the literature, a meta-analysis was performed using a median of median (MM) model. THC PMR towards peripheral blood is supported by a global estimate of 0.81 (CI95%: 0.51 to 1.2). Redistribution towards femoral blood appears to be stronger than towards iliac blood; indeed, the median estimate of C/P decreases to 0.64 (CI95%: 0.40 to 1.1) when studies with iliac blood were removed from the meta-analysis. THCCOOH PMR towards central blood is supported by a C/P median estimate of 1.3 (CI95%: 0.97 to 1.6). THC PMR can be suspected when these indicators are observed (i) high THC blood concentration (>50 ng/mL), (ii) THC C/P lower than 1.0 (iii) blood THC/THCCOOH concentration ratios greater than 1.0 and (iv) non-detectability of THCCOOH in urine. In postmortem samples, many factors may contribute to the overestimation of THC concentration, therefore a careful interpretation is required, relying on both central and peripheral blood samples.

Suitability of cardiac blood, brain tissue, and muscle tissue as alternative matrices for toxicological evaluation in postmortem cases

Drug concentrations in peripheral blood are often used to evaluate whether death was caused by drug intoxication. In some cases, peripheral blood is not available, and analytical results of alternative matrices should instead be used in the toxicological evaluation. However, reference concentrations of alternative matrices are few, which makes interpretation of results a challenge. In this study, concentrations of selected benzodiazepines, opioids, illicit drugs, and other commonly used drugs in postmortem femoral blood, cardiac blood, brain tissue, and muscle tissue are presented. Alternative matrix-to-femoral blood drug concentration ratios and correlations of blood and alternative matrix drug concentrations were calculated to examine which of the investigated alternative matrices were most suited to use for toxicological evaluation in cases where peripheral blood is not available. The results showed that concentrations in cardiac blood, brain tissue, and muscle tissue could be useful in the postmortem evaluation of most of the 19 selected analytes. In most cases, analytes were detected in all the alternative matrices. The median concentration ratios for the selected analytes in brain tissue, cardiac blood, and muscle tissue relative to femoral blood ranged from 0.57 to 3.42, 0.59 to 1.87, and 0.67 to 7.04, respectively. Overall, cardiac blood provided the concentrations most comparable with femoral blood concentrations, indicating that cardiac blood can be useful in cases where femoral blood is not available. However, the measured concentrations should be interpreted with caution.

Blackout Brownie: A Final Dessert Case Study

Cannabis products have been becoming more widely accepted as a recreational drug and for medicinal purposes to aid in various ailments. This paper reports a death after acute ingestion of an edible cannabis brownie. The 65-year-old female decedent with a history of chronic pain ingested an edible cannabis brownie after other alternative edibles and prescribed medication produced no desired effects. After consuming the cannabis product with her husband, both began feeling high and nauseated. The decedent was last seen alive by her husband stopped part way up the stairs prior to him going to sleep. She was found expired at the base of the stairs the following morning with no apparent trauma. The autopsy concluded the decedent was obese with severe ischemic cardiovascular disease. The toxicology report detected delta-9-tetrahydrocannabinol present at greater than 5000 ng/mL in the decedent's central blood at the time of sample collection. The final cause of death was ruled as natural due to cardiovascular disease with cannabis present in her system.

Distribution of tetrahydrocannabinol and cannabidiol in several different postmortem matrices

Cannabis is the most widely used illicit substance worldwide. A limited number of studies have investigated whether tetrahydrocannabinol (THC) and cannabidiol (CBD) can be detected in other postmortem matrices than blood and urine. The aim of this study was to investigate the distribution of THC and CBD in several different postmortem matrices. Concentrations in peripheral blood were compared to those in cardiac blood, pericardial fluid, psoas muscle, vastus lateralis muscle, and vitreous humor. A total of 39 postmortem forensic autopsy cases were included. THC and CBD were analyzed using gas chromatography-mass spectrometry. We were able to detect both THC and CBD in most of the analyzed matrices. For vitreous humor, however, only approximately 50% of the cases were available for analysis, and only two were found to be positive. Median concentrations in peripheral blood were 0.0040 (0.00042-0.056) mg/L for THC and 0.0013 (0-0.023) mg/L for CBD. The concentration ratios between pericardial fluid and cardiac blood compared to peripheral blood were< 1 for both THC and CBD for the majority of the cases. For THC, a median ratio of 0.60 (0.063-7.2) and 0.65 (0.068-4.8) were found for pericardial fluid and cardiac blood, respectively, compared to peripheral blood, whereas for CBD the corresponding median ratios were 0.40 (0.010-1.9) and 0.80 (0.017-2.4). The THC concentrations in psoas muscle and vastus lateralis muscle were high compared to those in peripheral blood in several cases, and large variations in the muscles to peripheral blood concentration ratios were seen. This was also the case for CBD. Our study shows that THC and CBD can be detected in postmortem matrices other than peripheral blood, and results from other matrices might provide important information in forensic cases where peripheral blood is not available. However, vitreous humor was not suitable for detecting neither THC nor CBD.

Cannabinoid distribution in fatally-injured pilots' postmortem fluids and tissues

The primary psychoactive component of cannabis, Δ⁹-tetrahydrocannabinol (THC) impairs cognitive function and psychomotor performance, particularly for complex tasks like piloting an aircraft. The Federal Aviation Administration's (FAA) Forensic Sciences Section at the Civil Aerospace Medical Institute (Oklahoma City, OK) performs toxicological analyses on pilots fatally injured in general aviation incidents, permitting cannabinoids measurement in a broad array of postmortem biological specimens. Cannabinoid concentrations in postmortem fluids and tissues from 10 pilots involved in airplane crashes are presented. Median (range) THC blood concentration was 1.6 (1.0-13.7) ng/mL. Phase I metabolites, 11-hydroxy-THC (11-OH-THC) and 11-nor-9-carboxy-THC (THCCOOH) and phase II glucuronide metabolite, THCCOOH-glucuronide, had median (range) blood concentrations of 1.4 (0.5-1.8), 9.9 (2.2-72.6) and 36.6 (7.1-160) ng/mL, respectively. Urine analyses revealed positive results for THCCOOH, THC-glucuronide, THCCOOH-glucuronide and 11-nor-9-carboxy-Δ⁹-tetrahydrocannabivarin (THCVCOOH). THC was readily distributed to lung, brain, kidney, spleen and heart. The psychoactive metabolite, 11-OH-THC, was identified in liver and brain with median (range) concentrations 7.1 (3.5-10.5) and 2.4 (2.0-6.0) ng/g, respectively. Substantial THCCOOH and THCCOOH-glucuronide concentrations were observed in liver, lung, brain, kidney, spleen and heart. These cannabinoid concentrations from multiple types of postmortem specimens add to the limited postmortem cannabinoid research data and suggest useful biological matrices for investigating cannabinoid-related deaths.

Postmortem Drug Redistribution: A Compilation of Postmortem/Antemortem Drug Concentration Ratios

Postmortem drug redistribution (PMR) is a well-known phenomenon in forensic toxicology with implications for medico-legal death investigations. Paired antemortem (AM) specimen and postmortem (PM) mortuary admission femoral blood drug concentrations from 811 coronial cases were used to construct a retrospective compilation of PM/AM drug concentration ratios for 42 parent drugs and metabolites. The median PM/AM ratios for all antidepressants were > 1 and consistent with PMR In contrast, the median PM/AM ratios of most benzodiazepines were < 1. The antipsychotics were varied (0.63-3.3) and suggest the mixed effects of PMR and drug instability. Amphetamines exhibited no trends (0.90-0.95) and are likely confounded by many factors. The PM/AM ratios of cardiovascular drugs, opioids and other drugs are also reported. This research represents an expansive retrospective compilation of paired AM and PM drug concentrations for many toxicologically relevant drugs. While the median PM/AM ratios demonstrate some drug-dependent trends, there was no obvious relationship between AM specimens and PM femoral blood taken at mortuary admission.