Oxycodone (OC) is an opioid with strong analgesic effects widely used to treat acute and chronic pain. Interpretation of OC concentrations in postmortem cases is complicated due to tolerance and overlapping concentrations for fatal and non-fatal levels. In this study, our aim was to develop and validate a method for OC and its three metabolites: noroxycodone (NOC), oxymorphone (OM) and noroxymorphone (NOM) in postmortem femoral blood. Our goal was to define reference concentrations for intoxications and non-intoxications and investigate metabolic ratios in different causes of death. A rapid LC-MS-MS method using protein-precipitated postmortem blood was developed. Lower limit of quantitation was 0.005 mu g/g blood for all analytes; upper limit of quantitation was 1.0 mu g/g for OC and NOC and 0.25 mu g/g for OM and NOM. The method displayed high precision (3.3-7.7%) and low bias (-0.3 to 12%). In total, 192 cases were analyzed and concentrations ranged from 0.005 to 13 mu g/g for OC, 0.005 to 2.0 mu g/g for NOC, 0.005 to 0.24 mu g/g for OM, and 0.005 to 0.075 mu g/g for NOM. We found a significant difference in OC concentration between the cases where OC contributed and those where it did not. In spite of that, we do not recommend the use of a specific blood concentration to distinguish fatal intoxications. Instead, the percentiles from our data set suggest that concentrations >0.2 mu g/g are likely to have contributed to toxicity, but that concentrations as high as 0.3 might be tolerated without toxic effects. In addition, we also found that a low NOC/OC ratio could point toward an acute fatal intoxication. In conclusion, the OC concentration alone may not be sufficient to diagnose a fatal intoxication.

Genetic disposition can cause variation in oxycodone pharmacokinetic characteristics and decrease or increase the expected clinical response. In forensic medicine, determination of cause of death or assessing time between drug intake and death can be facilitated by knowledge of parent and metabolite concentrations. In this study, the aim was to investigate if CYP2D6 genotyping can facilitate interpretation by investigating the frequency of the four CYP2D6 phenotypes, poor metabolizer, intermediate metabolizer, extensive metabolizer, and ultra-rapid metabolizer in postmortem cases, and to study if the CYP2D6 activity was associated with a certain cause of death, concentration, or metabolic ratio. Cases positive for oxycodone in femoral blood (n = 174) were genotyped by pyrosequencing for CYP2D6*3, *4, and *6 and concentrations of oxycodone, noroxycodone, oxymorphone, and noroxymorphone were determined by LC-MS/MS (LLOQ 0.005 mu g/g). Digital droplet PCR was used to determine the copy number variation for CYP2D6*5. Cases were categorized by cause of death. It was found that poor and intermediate CYP2D6 metabolizers had significantly higher oxycodone and noroxycodone concentrations compared to extensive and ultra-rapid metabolizers. CYP2D6 phenotype were equally distributed between cause of death groups, showing that no phenotype was overrepresented in any of the cause of death groups. We also found that the concentration ratio between oxymorphone and oxycodone depended on the CYP2D6 activity when death was unrelated to intoxication. In general, a low metabolite to parent ratio indicate an acute intake. By using receiver operating characteristic (ROC) analysis, we conclude that an oxymorphone/ oxycodone ratio lower than 0.075 has a high sensitivity for separating intoxications with oxycodone from other intoxications and non-intoxications. However, the phenotype needs to be known to reach a high specificity. Therefore, the ratio should not be used as a biomarker on its own to distinguish between different causes of death but needs to be complemented by genotyping.

Background and Objectives Oxycodone is frequently prescribed as well as detected in postmortem cases. Concurrent use of pharmacodynamically or pharmacokinetically interacting drugs can cause adverse effects or even fatal intoxication. The aims of this study were to investigate differences in prescriptions for and toxicological findings of pharmacodynamically and pharmacokinetically interacting drugs in fatal oxycodone-related intoxications and other causes of death. We also aimed to investigate the differences in prevalence of oxycodone prescriptions, and the detected postmortem oxycodone concentrations between fatal oxycodone-related intoxications and other causes of death. Methods Forensic autopsy cases (2012-2018) where oxycodone was identified in femoral blood (n = 1236) were included. Medical history and prescription data were retrieved from national databases and linked to the forensic toxicology findings. Results Oxycodone-related deaths were found to have higher blood concentrations of oxycodone (median 0.30 mu g/g vs. 0.05 mu g/g) and were less likely to have a prescription for oxycodone (OR 0.62) compared to nonintoxication deaths. Pharmacodynamically interacting drugs were prescribed in 79% and found in blood in 81% of the cases. Pharmacokinetically interacting drugs were rarely prescribed (1%). Oxycodone-related deaths were more likely to have prescriptions for a pharmacodynamically interacting drug (OR 1.7) and more often have co-findings of one or multiple pharmacodynamically interacting drugs (OR 5.6). Conclusion The results suggest that combined use of oxycodone and pharmacodynamically interacting drugs is associated with oxycodone-related death and that non-medical use of oxycodone is a potential risk factor for oxycodone-related intoxication.

Postmortem metabolomics has recently been suggested as a potential tool for discovering new biological markers able to assist in death investigations. Interpretation of oxycodone concentrations in postmortem cases is complicated, as oxycodone tolerance leads to overlapping concentrations for oxycodone intoxications versus non-intoxications. The primary aim of this study was to use postmortem metabolomics to identify potential endogenous biomarkers that discriminate between oxycodone-related intoxications and non-intoxications. Ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry data from 934 postmortem femoral blood samples, including oxycodone intoxications and controls positive and negative for oxycodone, were used in this study. Data were processed and evaluated with XCMS and SIMCA. A clear trend in group separation was observed between intoxications and controls, with a model sensitivity and specificity of 80% and 76%. Approximately halved levels of short-, medium-, and long-chain acylcarnitines were observed for oxycodone intoxications in comparison with controls (p < 0.001). These biochemical changes seem to relate to the toxicological effects of oxycodone and potentially acylcarnitines constituting a biologically relevant biomarker for opioid poisonings. More studies are needed in order to elucidate the potential of acylcarnitines as biomarker for oxycodone toxicity and their relation to CNS-depressant effects.