Postmortem acetaminophen pharmacokinetics: an experimental study of site and time-dependent concentration changes

Postmortem blood drug concentrations are obtained routinely for assessment of the cause of mortality. However, the relationship of postmortem drug concentration to blood concentrations at the time of death remains poorly characterized. Using Ketamine sedation, 10 New Zealand white rabbits were sacrificed 20 minutes after oral gavage with liquid acetaminophen 160 mg/kg as a model drug. Blood samples were obtained from peripheral (femoral vein) and central sites (heart & inferior cava) over time and compared with heart blood concentrations obtained at the time of sacrifice. The mean +/- SE antemortem acetaminophen concentration was 63.1 +/- 14.6 mcg/ml. Postmortem central blood concentrations were as follows: T = 3 h: 200.8 +/- 129.2 micrograms/mL, T = 6 h: 100.8 +/- 39.6 micrograms/mL and T = 12 h: 480.8 +/- 128.8 micrograms/mL. Postmortem peripheral site results were: T = 3 h: 50.2 +/- 21.4 micrograms/mL, T = 6 h: 100.8 +/- 18.1 and T = 12 h: 117.7 +/- 37.2 micrograms/mL. Overall, blood acetaminophen concentrations increased significantly over time for central sampling sites. Drug concentration increases seen in the central sampling sites were several times higher than that seen in peripheral blood. Blood samples taken from peripheral sites did not alter significantly. The results of this controlled study were consistent with previous autopsy case series and case reports suggesting that postmortem drug concentrations do not reflect premortem values. Variables affecting postmortem drug concentrations include both postmortem sampling time and anatomic blood collection site.