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.