Fentanyl postmortem redistribution: preliminary findings regarding the relationship among femoral blood and liver and heart tissue concentrations.

Postmortem redistribution refers to the process of drugs diffusing from tissues into blood along a concentration gradient between death and time of specimen collection at autopsy. Anatomical site-to-site variation can exist for drug concentrations. The purpose of this study was twofold. First femoral blood, liver, and heart fentanyl concentrations were compared in medical examiner cases to assist in determining which specimen most appropriately should be used for interpretation. Nine fentanyl-positive cases were identified by history of drug use over a 15-month period (2007-2008). Femoral blood fentanyl concentrations (n = 9) ranged from 2.7 to 52.5 microg/L, liver fentanyl tissue (n = 9) ranged from 37.0 to 179 microg/kg, and heart fentanyl tissue (n = 3) ranged from 52.8 to 179 microg/kg. Liver tissue to femoral blood ratios ranged from 0.85 to 35.8, and heart tissue to femoral blood ratios ranged from 1.9 to 5.4. Second, utilizing a published compendium of multiple postmortem drugs, liver and heart tissues to femoral blood drug ratios were compared to known volumes of distribution, solubilities, and pKa. No significant relationships were observed. In conclusion, establishing a larger evidence-based database using liver fentanyl concentrations may be more optimal than blood concentrations for interpretation of postmortem fentanyl concentrations in medical examiner and coroner cases.