Identification of postmortem product of amlodipine decomposition by hemoglobin with LC-Q-Orbitrap-MS

Amlodipine (AM), a dihydropyridine calcium channel blocker, is frequently prescribed for hypertension in the clinical setting. Because AM has been detected in various lethal poisoning and suicide cases, it is important to determine its precise concentration in postmortem blood to serve as definitive evidence of death by intoxication. However, blood AM concentration at autopsy frequently differs from that at the time of death. In this study, we found that AM undergoes dehydrogenation by H₂O₂ at temperatures ranging from 4 to 45ºC. Mass spectra measured by quadrupole-Orbitrap mass spectrometry hyphenated with liquid chromatography showed the generation of 3-ethyl 5-methyl 2-((2-aminoethoxy)methyl)-4-(2-chlorophenyl)-6-methylpyridine-3,5-dicarboxylate (AM-PDP-1) in H₂O₂ and Hb/H₂O₂ reaction solutions incubated with AM and in postmortem blood of persons who died of drowning, fire, disease, drug poisoning, CO poisoning, traumatic shock, falling, or choking, after intentional ingestion of AM. AM-PDP-1 is the novel postmortem degradation compound of AM in blood. This compound in the Hb/H₂O₂ reaction solution was more stable than AM at 4-45ºC. These results show that AM-PDP-1, formed by H₂O₂-mediated postmortem AM decomposition, is a potential biomarker to correct for AM concentration in postmortem blood.