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Caution against using reference tables

المؤلف:  Sue Jickells , Adam Negrusz (Editors)

المصدر:  Clarkes Analytical Forensic Toxicology

الجزء والصفحة:  P215-216

2026-10-14

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Caution against using reference tables

Interpretation of postmortem toxicology results can be very challenging and should only be done with a thorough knowledge of the case history, including autopsy findings, information from the scene and relevant medical history. It is not difficult to interpret a high blood strychnine concentration in a person found dead in a farmhouse together with an open container of strychnine-containing rodent poison and a suicide note. However, how should the toxicologist interpret a moderately high blood concentration of imipramine in an adolescent prescribed the drug for attention-deficit disorder. Could the drug have accumulated? Was the subject suffering from depression? Was he or she complaining of side-effects? Can any medication that remains be accounted for by the time since the prescription was filled and dosage (i.e. a medication count)? Did the autopsy reveal any significant natural disease? Was the behaviour of the subject observed in the immediate period leading to death? Was the death a sudden collapse which was witnessed? Was there a period of emergency hospitalisation leading up to death? If so, what did the medical assessment reveal? Are there any antemortem plasma or blood specimens still available? These are the types of questions that the forensic toxicologist should ask in cases that are anything less than straightforward. There is a great temptation for forensic toxicologists and others to refer to tables of thera peutic, toxic and fatal concentrations. While these tables may be of some use in clinical toxicology, they are of very limited value for the interpretation of postmortem toxicology results and can be very misleading. Such tables are often drawn extensively from clinical data, seldom take into account tolerance and do not provide for phenomena such as postmortem redistribution. For example, interpretation of morphine and other narcotic concentrations may be very dependent on how long the person has been prescribed the drug and at what dosage. The inappropriate use of tables can result in over and underestimation of the potential toxicity of a drug depending on the degree of tolerance developed, natural disease and whether other substances are present. The ranges given may not take into account the circumstances of drug use. For example, the therapeutic range for fentanyl when used intravenously as an adjunct to anaesthesia may be greater than 10-fold that after use for analgesia via a transdermal patch. Data compendia may also include cases in which there was a prolonged survival time and the person died from the sequelae of the intoxication (e.g. hypoxia, organ failure), but after medical intervention had prolonged life, resulting in lower blood concentrations. Specific references to case data and further information are lacking in most instances. Experienced post mortem toxicologists rely first on their own case experience, supplemented by compilations of drug monographs, where references to the original published work are available, and the circumstances of the case (Baselt 2002).

for analysis but also because of their possible state of decomposition; possible limitations of case history; the potential for any number of substances to be present and the difficulties of screening for all drugs and poisons together with the difficulties of interpretation of results. Despite all these potential difficulties, it can be a fascinating subject area because these difficulties pose interesting analytical and intellectual challenges not found in many occupations.