Postmortem redistribution of amphetamines and benzodiazepines in humans: Important variables that might be influencing the central blood / peripheral blood ratio.

INTRODUCTION: The primary objective of postmortem forensic toxicology is to determine if toxicological substances detected in bodily material of victims have contributed to the death of the victim. Interpretation of postmortem drug concentrations is hindered by the fact that time and site dependent variations in postmortem drug concentrations occur, as a result of postmortem redistribution (PMR). An often-used marker for the occurrence of PMR, is the cardiac blood concentration/peripheral blood concentration ratio (C/P ratio) of a drug. In this study, we investigated the relationship between 13 variables and the C/P ratios of amphetamines and benzodiazepines. METHOD: Toxicological results of all postmortem cases that were positive for amphetamines (amphetamine, MDMA, MDA) and/or benzodiazepines (diazepam, desmethyldiazepam, temazepam, oxazepam, midazolam, α-hydroxymidazolam) investigated by the Netherlands Forensic Institute between January 1 2010 and July 31 2020 were reviewed. A total of 112 amphetamine positive cases (224 paired specimen) and 179 benzodiazepine positive cases (358 paired specimen) were selected. The C/P ratios were determined for all selected cases. Ratios were compared between subgroups by performing either a Mann-Whitney U test or a Kruskal-Wallis test followed by post-hoc Mann-Whitney U test. RESULTS: After dividing cases in quartiles based on their amphetamine concentration in femoral blood, the amphetamine C/P ratio was significantly lower in cases with a high amphetamine concentration (quartile 4) compared to cases with a low amphetamine concentration (quartiles 1 and 2) with median C/P ratios of 1.6, 2.4 and 2.2, respectively (p-value<0.001 and p-value=0.001, respectively). The MDA C/P ratio was significantly higher in cases where trauma was the cause of death compared to cases where intoxication was the cause of death with median C/P ratios of 3.3 and 1.6, respectively (p-value<0.001). The MDA C/P ratio was also significantly lower in cases where resuscitation was attempted compared to cases where no resuscitation was attempted with median C/P ratios of 1.6 and 2.4, respectively (p-value=0.003). However, a significant dependency between the variables cause of death and attempted resuscitation was observed. No significant differences in benzodiazepine C/P ratios were observed between subgroups of any of the investigated variables. However, the low p-value of BMI suggests a potential difference in midazolam C/P ratio between BMI subgroups (p-value=0.027). CONCLUSION: When interpreting postmortem toxicological results, it might prove useful to take the above-mentioned variables into account.

Postmortem redistribution of cocaine and its metabolites, benzoylecgonine and ecgonine methyl ester in humans: Important variables that might be influencing the central blood / peripheral blood ratio.

INTRODUCTION: A big challenge in forensic toxicology is the correct interpretation of the results of quantitative analyses in postmortem cases. Postmortem drug concentrations not necessarily reflect the drug concentrations at the time of death, due to postmortem changes in drug concentrations caused by postmortem redistribution (PMR). Cardiac blood is more prone to PMR related concentration changes than peripheral blood. Because of this difference in susceptibility to PMR related concentration changes, the ratio of cardiac blood concentration/peripheral blood concentration (C/P) of a drug is an often-used marker of PMR. In this study, we investigated the relationship between different potentially significant variables and the C/P ratios of cocaine, benzoylecgonine (BE) and ecgonine methyl ester (EME) in humans. The aim was to elucidate the mechanisms involved in PMR of these substances and potentially provide guidelines aiding forensic toxicologists in the interpretation of postmortem quantitative results of cocaine and its metabolites. To differentiate between postmortem concentration changes due to redistribution versus degradation of cocaine, the relationships between these variables and metabolite/cocaine ratios were investigated as well. METHOD: Toxicological results of all postmortem cases that were positive for cocaine, BE and/or EME investigated by the Netherlands Forensic Institute between January 1st 2010 and July 31st 2020 were reviewed. The C/P ratios, BE/cocaine ratios and EME/cocaine ratios were determined for all selected cases. Cocaine, BE and/or EME were quantified in both femoral blood and cardiac blood in a total of 148 cases. Ratios were compared between subgroups by performing either a Mann-Whitney U test or a Kruskal-Wallis test followed by post-hoc Mann-Whitney U test. RESULTS: A statistically significant difference in C/P ratio of EME was observed between trauma and non-trauma cases with median C/P ratios of 2.03 and 1.57, respectively (p value=0.001). A statistically significant difference in EME/cocaine ratio was observed between the BMI subgroups 18.5 - 25.0 kg/m2 and> 25 kg/m2 with median EME/cocaine ratios of 3.79 and 1.58, respectively (p-value<0.001). CONCLUSION: Postmortem cocaine concentrations should be interpreted with caution, considering the occurrence of both PMR and postmortem degradation. When interpreting postmortem toxicological results in cocaine-related fatalities, it might prove useful to take the above-mentioned variables into account.