Early-phase postmortem redistribution of the enantiomers of citalopram and its demethylated metabolites in rats

Abstract

The aim of this study was to investigate the early-phase postmortem redistribution of the enantiomers of citalopram (CIT) and its metabolites demethylcitalopram (DCIT) and didemethylcitalopram (DDCIT) in a rat model. Furthermore, we wanted to examine the role of the lungs as a reservoir of postmortem drug release and to investigate the influence of storage temperature (21°C vs. 4°C) on postmortem changes. Rats were administered a single CIT dose of 100 mg/kg (s.c.), and heart blood and lung samples were collected antemortem and 15 min postmortem for enantioselective high-performance liquid chromatographic analysis. About three times higher blood drug and metabolite levels were observed in the postmortem rats than in the antemortem rats (p < 0.0001). Refrigeration at 4°C did not prevent, but significantly reduced, the postmortem increase in heart blood CIT levels as compared to the concentrations in the rats stored at 21°C (p < 0.05). The lung drug concentrations were lower postmortem than antemortem (p < 0.05). The enantiomeric (S/R) concentration ratios of CIT and metabolites in blood and lungs were of similar magnitude before and after death. The parent-drug-to- metabolite ratios for CIT/DCIT were unchanged after death. In conclusion, this study shows that heart blood CIT and metabolite levels increase rapidly after death. Further, a fall in postmortem CIT concentrations in the lungs was observed, indicating that the lungs seemed to represent one major source of drug release during early-phase postmortem redistribution.