Entomological consequences and toxicological detection of synthetic cannabinoid receptor agonists (SCRAs) in necrophagous larvae (Diptera: Calliphoridae)

Forensic entomologists estimate minimum post-mortem intervals (PMI_min) by measuring the development of larvae on decomposing bodies. Entomotoxicology assumes significance when the deceased had ingested drugs, as these may alter insect development and consequently the accuracy of PMI_min estimations. 5F-ADB, ADB-BUTINACA, and MDMB-4en-PINACA are potent synthetic cannabinoid receptor agonists and drugs of abuse, linked to human intoxications and deaths. We investigated the impact of 5F-ADB on the development of Lucilia sericata (Meigen, 1826) (Diptera: Calliphoridae) larvae and developed a method to detect 5F-ADB, ADB-BUTINACA, MDMB-4en-PINACA, and their metabolites in larvae by liquid chromatography-mass spectrometry. Neonate larvae were exposed to 5F-ADB concentrations that reflect those in human post-mortem specimens. At precise intervals, larvae were killed in near-boiling water, dried, and then their size measured, followed by toxicological analysis. ANOVA demonstrated that only time (= age) significantly affected larval length and mass (through growth). Drug concentrations typically found in post-mortem peripheral blood did not significantly affect larval development, suggesting that 5F-ADB in a corpse would not influence PMI_min estimation with L. sericata. 5F-ADB was detected in trace amounts in larvae that were exposed to post-mortem peripheral blood concentrations. Most larvae from higher concentration treatments contained 5F-ADB levels above the limit of detection of 0.25 µg/kg, but not all samples tested positive. Post-feeding larvae mostly did not contain detectable levels of 5F-ADB, and metabolites were found in none of the larval samples. Actively feeding L. sericata larvae from a corpse may thus be useful to qualitatively identify a prior consumption of 5F-ADB by the deceased.