Postmortem drug concentration intervals for the non-intoxicated state – A review

In postmortem toxicology, it is important to know what the usual drug level is in blood under ordinary therapy to make correct interpretations with regard to the possible occurrence of poisoning. A commonly used source is The International Association of Forensic Toxicologists (TIAFT) list of drug concentrations providing therapeutic drug levels, usually measured in serum. In this article, published postmortem-derived blood drug reference concentration intervals were related to therapeutic serum levels of drugs from the TIAFT list to assess agreement or discrepancies with focus on the importance of postmortem redistribution. The ratio between the upper limits was evaluated. This ratio ranged from 0.13 to 11.3 for 57 compounds with a median value of 1.5. For about a third of the compounds the ratio exceeded three. There was a tendency that for highly water-soluble drugs with a low propensity for redistribution, the ratio was generally low. For example, for pentobarbital, carisoprodol, meprobamate, carbamazepine, phenazone and theophylline, the ratio ranged from 0.14 to 1.1 with a median of 0.4. For the 15 antidepressants considered, on the other hand, the ratio was relatively high, ranging from 0.6 to 4.7 (median 2.4). For antipsychotics, the ratio ranged from 0.2 to 11.3 with a median of 1.4. In conclusion, there were generally wide discrepancies between serum-based intervals as presented in the TIAFT list and published postmortem blood-based drug reference intervals. More focus on postmortem-derived intervals is encouraged, so that those that have been estimated are cited in reference publications and so that further intervals are estimated. Ultimately, a reliable database of postmortem blood-based drug reference intervals for use by the forensic community is desirable.