https://www.investigativemedia.com/wp-content/uploads/2015/12/477152039a27dab9ffc06ffdb49e292c.pdf

Interpreting results of ethanol analysis in postmortem specimens: A review of the literature

Postmortem drug concentrations do not necessarily reflect concentrations at the time of death, as drug levels may vary according to the sampling site and the interval between death and specimen collection. These site- and time-dependent variations are called "postmortem redistribution" (PMR). The underlying mechanisms are complex and of different types. Passive drug release from drug reservoirs such as the gastrointestinal tract, liver, lungs, and myocardium may occur immediately after death and, later on, cell autolysis and the putrefactive process participate in redistribution. There is evidence that basic lipophilic drugs with a large distribution volume are particularly susceptible to PMR. Nevertheless, this cannot explain the actual PMR of some nonbasic, nonlipophilic drugs. In addition, the persistence of drug metabolism immediately after death must be considered. Consequently, it is of great importance to analyze specimens from different sampling sites in order to detect potential PMR and avoid misinterpretation of results.

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Mechanisms underlying postmortem redistribution of drugs: a review.

Preanalytic aspects in postmortem toxicology.

Forensic toxicology is defined as the application of toxicology for the purposes of the law. Until the middle of the twentieth century, forensic toxicology was practiced almost exclusively as a result of investigating a fatality. Therefore, analyses were performed on specimens from deceased individuals. Today, forensic pathologists rely heavily upon forensic toxicology testing to determine how alcohol, drugs, or poisons may have caused or contributed to death.

Principles of Forensic Toxicology

Clinical pharmacology assumes that deductions can be made about the concentrations of drugs from a knowledge of the pharmacokinetic parameters in an individual; and that the effects are related to the measured concentration. Post-mortem changes render the assumptions of clinical pharmacology largely invalid, and make the interpretation of concentrations measured in post-mortem samples difficult or impossible. Qualitative tests can show the presence of substances that were not present in life, and can fail to detect substances that led to death. Quantitative analysis is subject to error in itself, and because post-mortem concentrations vary in largely unpredictable ways with the site and time of sampling, as a result of the phenomenon of post-mortem redistribution. Consequently, compilations of ‘lethal concentrations’ are misleading. There is a lack of adequate studies of the true relationship between fatal events and the concentrations that can be measured subsequently, but without such studies, clinical pharmacologists and others should be wary of interpreting post-mortem measurements.

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Post-mortem clinical pharmacology

Aims —To compare blood drug concentrations during life with postmortem drug concentrations measured from a peripheral site and a central site. Methods —Coroner9s cases from October 1990 to July 1997 were reviewed. Six cases had data on both antemortem and postmortem blood drug concentrations. The postmortem to antemortem ratio was compared with the postmortem central to peripheral ratio, using cardiac blood as a central site and femoral blood as a peripheral site. Results —Drugs that have a high postmortem central to peripheral ratio; that is, drugs that exhibit considerable postmortem redistribution, also have high postmortem to antemortem ratios. Conclusions —A large degree of error can arise from attempting to estimate antemortem drug concentrations and the ingested dose from postmortem measurements. The chosen site and technique for postmortem blood sampling can greatly influence the concentration of drug measured.

https://jcp.bmj.com/content/jclinpath/53/4/282.full.pdf

K A Hale

Papers

Estimating antemortem drug concentrations from postmortem blood samples: the influence of postmortem redistribution.