A reported 16-fold median postmortem/antemortem pholcodine ratio was not a universal measure of redistribution. In the same study, restricting the comparison to earlier whole-blood specimens produced a median ratio of 5.0. Specimen type was part of what the ratio compared.
What was the underlying study?
Mantinieks and colleagues compiled 811 hospital-death coronial cases from Victoria, Australia, reported during 2009–2017. They compared earlier clinical specimens with femoral blood taken at mortuary admission, reporting 42 drugs and metabolites with at least ten pairs each. Pholcodine had 16 pairs, not 811.
The clinical specimens could be whole blood, plasma or serum. The institute generally selected samples taken closest to hospital admission, rather than closest to death. These were not necessarily terminal concentrations.
Postmortem femoral blood, approximately 2–5 mL, was obtained by leg puncture as soon as practicable after mortuary admission. It was preserved with 1% w/v sodium fluoride and potassium oxalate, stored at 4°C and typically analyzed within 24 hours. Earlier specimens were typically stored at −20°C after receipt.
What did the 16 pholcodine pairs show?
The median earlier concentration was 0.015 mg/L, range 0.002–0.072 mg/L. The median postmortem concentration was 0.18 mg/L, range 0.001–0.69 mg/L. The median of the individual postmortem/antemortem ratios was 16, with a range of 0.24–47. The paired comparison was statistically significant, p = 0.001.
The median earlier-sample-to-death interval was 20 hours, and the median death-to-postmortem-collection interval was 17 hours. These intervals include an antemortem period in which drug disposition or further administration could have occurred; they are not a controlled postmortem-only time course.
The ratio of the two group medians is also not the median of the individual ratios. Each reported summary must retain its own calculation and denominator.
What changed when both specimens were whole blood?
About 35% of the study’s earlier specimens overall were plasma or serum. Pholcodine can distribute unevenly between blood components, so comparing those matrices with later whole blood can contribute to the numerical difference.
When the authors restricted the pholcodine comparison to the seven cases with earlier whole blood, the median ratio was 5.0, range 0.24–17. This was a smaller subset of different available cases. It was not a paired experiment measuring serum, plasma and whole blood in every one of the original 16 people.
The result shows why matrix identity matters. It does not establish that the change from 16 to 5.0 was entirely caused by matrix partitioning, or validate either number as an adjustment for a new case.
Redistribution was plausible but not isolated
The authors considered pholcodine’s physicochemical properties and tissue accumulation compatible with redistribution. The paired observations did not directly measure release from each person’s tissue reservoirs or separate it from all other processes.
Incomplete medical records prevented reliable identification of medication administered after the earlier specimen. Last-dose timing, incomplete distribution and individual pharmacokinetic differences were also unknown. Blind femoral puncture carried a possible contamination limitation. The included bodies were not obviously traumatized, burned or decomposed, limiting extrapolation to those conditions.
How were concentrations established?
Routine toxicology included validated LC–MS/MS procedures. The article referred to earlier method publications; it did not provide a pholcodine-specific numerical detection limit or complete validation table. It should not be described as demonstrating analytical performance beyond what it actually reported.
A drug measurement is also different from proof that the drug caused death. The concentration pairs did not establish a lethal threshold, impairment boundary or administered dose.
What belongs beside a quoted ratio?
Keep specimen type, anatomical site, both collection times, units and the number of pairs attached to the statistic. No valid individual predeath concentration results from simply dividing postmortem pholcodine by 16 or 5.0.
For related collection-time evidence, see why later postmortem drug results can rise, fall or remain similar.
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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