A lower postmortem quetiapine concentration does not identify a single degradation mechanism or exclude an earlier toxic exposure. A hospital-to-mortuary study found lower later concentrations in most of 30 paired cases, but specimen type, time before death and incomplete treatment records complicated the comparison.
Thirty quetiapine pairs within a larger compilation
Mantinieks and colleagues reviewed 811 hospital-death coronial cases from Victoria, Australia, during 2009–2017. Their compilation reported 42 drugs and metabolites with at least ten paired earlier and postmortem results each. Quetiapine contributed 30 pairs.
The earlier clinical specimen could be whole blood, serum or plasma. The institute generally analyzed the sample collected closest to hospital admission. It was not necessarily a sample taken just before death.
Postmortem blood was approximately 2–5 mL collected by leg puncture from the femoral region after mortuary admission. Samples contained 1% w/v sodium fluoride and potassium oxalate, were refrigerated at 4°C and were typically analyzed within 24 hours. Earlier specimens were typically frozen at −20°C after receipt.
What did the paired concentrations show?
The median earlier quetiapine concentration was 0.19 mg/L, range 0.027–0.75 mg/L. The postmortem median was 0.080 mg/L, range 0.011–1.7 mg/L. The median of individual postmortem/antemortem ratios was 0.55, range 0.03–2.5. The paired difference was statistically significant, p = 0.02.
The authors described a net reduction in 22 of the 30 cases. This was a directional observation between the collected specimens. The individual range also included later concentrations above earlier values, so the group result did not establish that quetiapine always falls.
The median interval from earlier collection to death was 20 hours, while the median death-to-postmortem collection interval was 19 hours. Changes during those two periods could not be separated by comparing only the endpoints.
Why “breakdown” did not identify when or how the change occurred
The paper discussed drug instability and used the term net breakdown. The retrospective design did not experimentally apportion each decrease among antemortem elimination, matrix differences, postmortem redistribution and degradation.
About 35% of the earlier specimens overall were plasma or serum. Quetiapine partitions differently between those matrices and whole blood. Restricting the quetiapine comparison to earlier whole blood raised the median ratio to 0.76. That subset analysis highlighted a matrix influence without supplying a universal conversion.
Last-dose timing and individual pharmacokinetics were unknown. Incomplete clinical records also prevented reliable identification of drugs given after the earlier specimen. The first sample therefore could not automatically be treated as the person’s concentration at death.
What did the cause-of-death observations add?
Five quetiapine cases were attributed to mixed-drug toxicity. Only one, identified in the paper as case 26, specifically attributed quetiapine as a main contributor. These were case interpretations within an observational series, not a concentration-threshold experiment.
A lower later value cannot by itself establish that quetiapine was irrelevant earlier. Conversely, an earlier positive finding does not independently prove quetiapine caused death. The complete treatment history, pathology and other substances remain relevant.
The analytical and sampling boundaries
Routine toxicology included validated LC–MS/MS procedures. The article referred to earlier analytical methods rather than supplying a complete quetiapine validation table. It did not establish a new impairment cutoff or a dose-to-concentration model.
Femoral collection used blind puncture, which the authors recognized could introduce blood or fluid from elsewhere. The bodies were not obviously traumatized, burned or decomposed. These selection and collection conditions should not be generalized silently to advanced decomposition or extensive injury.
What should be retained in an individual review?
Preserve the actual earlier matrix, collection times, femoral collection method, both concentrations and their units. Dividing a postmortem concentration by 0.55 or 0.76 would not recover a validated individual predeath value. The observed paired decrease and its possible causes should remain separate statements.
A different reporting issue arises when quetiapine is identified below the quantitation limit; detection there must remain distinct from an exact concentration.
Primary source
Mantinieks D, Gerostamoulos D, Glowacki L, et al. Postmortem Drug Redistribution: A Compilation of Postmortem/Antemortem Drug Concentration Ratios. Journal of Analytical Toxicology. 2021;45:368–377. doi:10.1093/jat/bkaa107.
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