Superiority of postmortem liver fentanyl concentrations over peripheral blood influenced by postmortem interval for determination of fentanyl toxicity

Abstract Objective The current study was undertaken to determine the relationship between postmortem (PM) peripheral blood (PB) and liver fentanyl concentrations and the role of measuring liver fentanyl concentrations in cause of death investigations in medical examiner cases in which fentanyl was identified. Design and methods FB and liver tissue were routinely collected at autopsy from 4 Minnesota medical examiners' offices in 2010–2011. Samples were analyzed by gas chromatography–mass spectrometry (GC–MS). Results PB fentanyl ranged from  56 μg/kg, without substantial overlap as found in blood fentanyl concentrations. Conclusion Discriminatory liver fentanyl concentrations suggestive of therapeutic or toxic drug levels may better assist cause of death determination in cases of suspected fentanyl toxicity than postmortem PB concentrations. Peripheral blood fentanyl concentrations appear to undergo postmortem redistribution, associated with an increasing PM interval.