Comparative analysis of fatal methadone poisonings based on chemical toxicological and forensic chemical investigations in Saint Petersburg in 2020–2022: a cross-sectional study

BACKGROUND: For many years, methadone poisoning has remained one of the leading causes of death among patients admitted to toxicology departments worldwide. During the COVID-19 pandemic, the number of such patients increased substantially, which may be associated with heightened anxiety, fear, sadness, adaptation difficulties, symptoms of post-traumatic stress disorder, and suicidal tendencies in both the general population and specific subgroups, thereby increasing the risk of drug and alcohol use as maladaptive coping strategies.

AIM: To perform a comparative analysis and evaluate the results of methadone detection based on retrospective data from chemical toxicological and forensic chemical investigations conducted in 2020–2022.

METHODS: This cross-sectional multicenter sample study employed retrospective medical data from patients who died of acute methadone poisoning. The analysis assessed features of methadone detection in fatal acute poisonings, the comparability of chemical toxicological and forensic chemical investigation results, and the frequency of circumstances affecting interpretation of the obtained findings.

RESULTS: The study included data from 131 cases of fatal methadone poisoning. In all reviewed cases, screening in chemical toxicological investigations was performed using immunochromatographic assay. In 20% of cases, the assay was performed 12–48 hours after hospital admission. False-positive methadone detection results in chemical toxicological investigations were recorded in 3.4% of cases, whereas false-negative results were found in 6%. In addition, confirmatory methods were not used in 18% of cases. Moreover, in all cases with false-negative results, high concentrations of substances such as nicotine and caffeine were detected in the samples, which may have affected the reliability of immunochromatographic assay.

CONCLUSION: Improving approaches to the selection of biological material, the timing of assay, and the mandatory use of confirmatory methods may minimize the risk of false-positive and false-negative methadone test results in chemical toxicological investigations. This, in turn, may improve diagnostic accuracy, optimize treatment strategy, and provide a more objective assessment of medical circumstances in subsequent forensic medical examinations.