A diphenylmethoxyacetic acid-to-diphenhydramine ratio may inform an exposure interpretation, but the Berlin autopsy series did not validate it as an exact ingestion clock. Its timing estimates applied an earlier interpretive scheme to selected cases rather than testing predictions against independently known administration times.
Which ratio was used?
Diphenhydramine, abbreviated DPH, is the parent drug. Diphenylmethoxyacetic acid, or DPMA, is a metabolite. Eckes and colleagues considered the quotient of their blood concentrations, DPMA divided by DPH, when discussing survival after intake.
The study reviewed 8,131 Berlin autopsies performed from January 2000 through December 2010, found 73 cases with DPH detection, and selected 20 suicidal intoxication cases for detailed analysis. These were retrospective death investigations, not controlled drug-administration experiments.
What did the original case examples report?
A 45-year-old man had peripheral-blood DPH at 2.02 µg/mL and trimipramine at 6.51 µg/mL. A DPMA/DPH quotient of 1.2 was interpreted by the authors, using the earlier scheme, as suggesting survival longer than ten hours after intake. The case involved combined intoxication.
An 81-year-old woman had DPH at 3.59 µg/mL and DPMA at 1.13 µg/mL. The reported quotient of 0.3 was interpreted as suggesting less than five hours. Her body was discovered after approximately 67 days, with putrefactive change; the short suggested survival interval was not the postmortem interval.
A 21-year-old woman had peripheral-blood DPH at 28.5 µg/mL and DPMA at 2.0 µg/mL. The quotient of 0.07 was also interpreted as less than five hours. Her approximate postmortem interval was two days. These were the authors’ timing interpretations, not independently observed dose-to-death durations.
Survival time and time since death answer different questions
A proposed interval from ingestion to death does not establish when the person died, when the body was discovered, or when the specimen was collected. Mixing those intervals can produce a seemingly precise chronology that the measurements do not support.
The specimens were obtained at autopsy and analyzed by high-performance liquid chromatography. Blood was generally femoral unless the study specified cardiac-only sampling. Detailed analytical methods were referenced elsewhere; the report did not give a complete validation of timing predictions or a matrix-specific uncertainty budget for the ratios.
Why the quotient can change without becoming a clock
The authors themselves cautioned that DPH and DPMA have different distribution volumes and may not remain sufficiently correlated after death. A ratio depends on both concentrations. It cannot be assumed stable merely because parent and metabolite originate from the same exposure.
The case series did not experimentally separate metabolism during life from redistribution, degradation or other changes after death. It also did not establish prediction errors across the varied postmortem intervals. The paper therefore supplies no demonstrated precision for dating an individual’s final intake from one autopsy ratio.
How to report a timing opinion accurately
State the measured compounds, specimen site, units, quotient and the source of the interpretive scheme. Attribute the suggested interval to the authors and identify what independent chronology is available. Do not convert a broad suggested interval into an exact administration time.
A metabolite ratio does not independently establish dose, impairment or cause of death. For a separate timing limitation, see why serial postmortem concentration changes do not provide a universal hourly correction.
Primary source
Eckes L, Tsokos M, Herre S, Gapert R, Hartwig S. Toxicological identification of diphenhydramine (DPH) in suicide. Forensic Science, Medicine, and Pathology. 2013;9:145–153. Published online 2012. doi:10.1007/s12024-012-9383-5.
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