Brain tissue can add useful evidence when postmortem MDMB-CHMICA exposure is suspected, but its concentration cannot simply be substituted for a blood result. A 2018 case report found the synthetic cannabinoid in every specimen examined, with the highest measured tissue concentration in brain. This was one extensively investigated death, not validation of a universal specimen hierarchy.
One traumatic death with several co-exposures
Gaunitz and colleagues investigated a 27-year-old man who died after falling from the 24th floor of a building. Autopsy approximately 12 hours after death documented severe trauma. Samples included cardiac and femoral blood, urine, psoas major muscle, brain, liver, right lung, kidney and gastric content. The right lung, liver, kidney and stomach were described as uninjured; the head and upper body had substantial injuries.
Femoral blood contained MDMB-CHMICA at 1.7 ng/mL, THC at 9.3 ng/mL, amphetamine at 1,050 ng/mL and MDMA at 275 ng/mL. Additional findings included low-level or trace drug signals in other specimens. These co-exposures prevent treating the case as an isolated MDMB-CHMICA experiment. The authors could not determine whether the fall was accidental or associated with a drug-induced mental state.
The specimen-specific findings
MDMB-CHMICA measured 2.1 ng/mL in cardiac blood and 1.7 ng/mL in femoral blood. Tissue results included 5.5 ng/g in brain, 3.8 ng/g in kidney, 2.6 ng/g in liver and lung, and 1.2 ng/g in psoas major muscle. Urine contained 0.01 ng/mL. Gastric content contained 2.4 ng/g, corresponding to approximately 1.1 µg in the collected gastric contents.
The units must remain attached to the specimen. A tissue result in ng/g is not the same measurement as blood in ng/mL. These observations did not establish a conversion between brain and blood, and a higher numerical tissue result does not independently establish a greater pharmacological effect.
Gastric detection also did not prove oral ingestion. The authors discussed diffusion and a likely nonoral route, with inhalation considered plausible. No witnessed route or known administered dose was established by the distribution measurements.
How quantitation differed between matrices
Analysis used liquid chromatography–electrospray tandem mass spectrometry. Most specimens were quantified by five-point standard addition, in which known amounts of analyte were added to the specimen. Insufficient material prevented that approach for urine and lung; those specimens used three-point matrix calibration instead.
Calibration R² exceeded 0.99 except for brain, where it was 0.98. Selected detection limits were 0.005 ng/mL in urine, 0.05 ng/mL in femoral blood, 0.025 ng/g in kidney and 0.017 ng/g in brain, defined by a signal-to-noise ratio of at least three. These detection limits are not a complete set of quantitation limits or uncertainty estimates for every specimen.
High-resolution analysis of reference material and the urine and kidney specimens supported identification of MDMB-CHMICA and distinguished it from BB-22, which can have similar nominal-mass fragmentation. The two compounds have different exact masses. This identification step was separate from comparing how much drug occurred in different tissues.
What the blood ratio did not establish
The cardiac/femoral ratio was approximately 1.2. The authors interpreted it as not indicative of appreciable redistribution in this case. However, no antemortem concentration or serial postmortem collection was available. Similar concentrations at two postmortem sites cannot demonstrate that neither changed after death.
The approximately 12-hour collection interval likewise did not establish a general time at which redistribution becomes complete. The case supplies a distribution snapshot, with trauma and multiple drugs, rather than a time-course experiment. Our discussion of central-to-peripheral ratios near one explains that broader distinction.
Using the result without overstating it
The report supports considering brain among available specimens and retaining companion blood and tissue results. It does not supply an individual fatal threshold, a reconstruction of the dose, or proof that MDMB-CHMICA caused the fall. Collection site, matrix, analytical procedure and case circumstances remain necessary to interpretation. For related analytical issues, see authentic specimens and assay interference.
Primary source
Gaunitz F, Lehmann S, Thomas A, Thevis M, Rothschild MA, Mercer-Chalmers-Bender K. Post-mortem distribution of the synthetic cannabinoid MDMB-CHMICA and its metabolites in a case of combined drug intoxication. International Journal of Legal Medicine. 2018;132:1645–1657. https://doi.org/10.1007/s00414-018-1911-8.
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