14 - Interpretive Considerations of Postmortem Blood Concentrations

Abstract

The determination of a fatal drug intoxication as the cause of death or drug intoxication as a contributing factor is a challenge for the toxicologist and pathologist. There are no hard “rules or guidelines” for the interpretation of postmortem toxicological results. As with the interpretation of any laboratory result, one must consider the case in totality. In the postmortem arena, this would include but is not limited to: prior medical history and intervention, scene investigation, anatomical findings or lack thereof, and toxicological results. There are other factors that come into play when interpreting postmortem toxicological results as well; clinical “therapeutic” versus postmortem “therapeutic” drug concentrations, whole blood to serum/plasma ratios, parent to metabolite ratios, postmortem redistribution, and tolerance. Drug–drug interaction further complicates the interpretation, one drug may induce metabolic enzymes and increase the clearance of the other drug or one drug may inhibit the metabolism of the other drug, leading to potentially toxic concentrations. The age and health of the decedent must also be included in the evaluation for they may impact drug clearance; both impacting the clearance of a drug.