Postmortem Oxycodone Toxicology: A Systematic Review and Meta-Analysis of Concentrations and Interpretative Markers

Background: Oxycodone is a widely prescribed semi-synthetic opioid central to pain management. However, establishing its role in death when detected in postmortem toxicology is challenging. Quantitative evidence to support forensic interpretation remains limited. Methods: A systematic review and meta-analysis was conducted following PRISMA 2020 guidelines. PubMed and Scopus were searched through 3 March 2026, for studies reporting quantitative postmortem oxycodone concentrations in human biological matrices. Peripheral blood was predefined as the primary matrix for quantitative synthesis. Random-effects meta-analysis with restricted maximum likelihood estimation was performed on logarithmically transformed concentrations to compare fatal intoxications versus non-intoxication deaths and mono- versus mixed-intoxication cases. Pooled estimates were reported as geometric mean concentrations with 95% confidence and prediction intervals. Secondary analyses evaluated metabolite-to-parent ratios, alternative matrices, and postmortem interval (PMI). Results: Twenty-three studies comprising 4335 oxycodone-positive decedents were included in the qualitative synthesis, and 14 studies in the quantitative meta-analysis. Fatal intoxication cases (n = 1555) showed a pooled geometric mean peripheral blood oxycodone concentration of 0.37 mg/L (95% CI: 0.24-0.58; I² = 93.5%), compared with 0.08 mg/L (95% CI: 0.04-0.15; I² = 98.5%) in non-intoxication deaths (n = 1409). Mono-intoxication cases (n = 135) exhibited higher concentrations (0.52 mg/L; 95% CI: 0.22-1.21; I² = 82.3%) than mixed-drug fatalities (n = 511; 0.29 mg/L; 95% CI: 0.13-0.65; I² = 93.1%). Metabolite data indicated that noroxycodone and oxymorphone patterns may assist in distinguishing acute intake and metabolic variability. Alternative matrices, particularly vitreous humor and solid tissues provided complementary interpretative information, while PMI contributed concentration variability. Conclusions: The key quantitative findings of this meta-analysis indicate higher peripheral blood oxycodone levels in fatal intoxications than in non-intoxication deaths. However, substantial heterogeneity precludes the definition of absolute concentration cut-offs, emphasizing the need to approach postmortem oxycodone interpretation within a probabilistic forensic framework integrating circumstantial evidence, sampling time, metabolite ratios, and data from alternative biological matrices.