Investigations into the stability of 17 psychoactive drugs in a “simulated postmortem blood” model

Abstract

In the postmortem environment, some drugs and metabolites may degrade due to microbial activity, even forming degradation products that are not produced in humans. Consequently, underestimation or overestimation of perimortem drug concentrations or even false negatives are possible when analyzing postmortem specimens. Therefore, understanding whether medications may be susceptible to microbial degradation is critical in order to ensure that reliable detection and quantitation of drugs and their degradation products is achieved in toxicology screening methods. In this study, a “simulated postmortem blood” model constructed of antemortem human whole blood inoculated with a broad population of human fecal microorganisms was used to investigate the stability of 17 antidepressant and antipsychotic drugs. Microbial communities present in the experiments were determined to be relevant to postmortem blood microorganisms by 16S rRNA sequencing analyses. After 7 days of exposure to the community at 37°C, drug stability was evaluated using liquid chromatography coupled with diode array detection (LC‐DAD) and with quadrupole time‐of‐flight mass spectrometry (LC‐QTOF‐MS). Most of the investigated drugs were found to be stable in inoculated samples and noninoculated controls. However, the 1,2‐benzisothiazole antipsychotics, ziprasidone and lurasidone, were found to degrade at a rate comparable with the known labile control, risperidone. In longer experiments (7 to 12 months), where specimens were stored at −20°C, 4°C, and ambient temperature, N‐dealkylation degradation products were detected for many of the drugs, with greater formation in specimens stored at −20°C than at 4°C.

In vitro degradation of ziprasidone in human whole blood

“…Compared with the quantitative experiment, 27 degradation was similar after 5 days at 37°C in the qualitative experiment, that is, ZIPR degraded to below the LOD of the LC‐DAD method in all blood specimens.…”

“…The majority of chemicals and materials have been described previously 27 . Ammonia (analytical grade, 30%) and ethyl acetate (99%) were obtained from ChemSupply (Gillman, SA, Australia).…”

“…In triplicate, methanol working solutions of ZIPR were spiked into clear autosampler vials and ethanol, acetone, glacial acetic acid, or acetaldehyde (500 μl) added to afford a ZIPR concentration of ~5 μg/ml. Vials were stored at ambient temperature in the dark for 7 days and analyzed by the LC‐DAD method previously detailed 27 . Aliquots were also collected and diluted fivefold with each respective solvent prior to LC‐QTOF‐MS analysis using the method previously detailed 27 .…”

“…and initial extracts collected using wide-bore sterilized pipette tips with filters and the unbuffered LLE method. 27 Specimens were then incubated at 37 C in the dark. Extracts were prepared from specimens every day at the same time each day for 4 days and then on a seventh day, with incubation at 37 C between sample collection.…”

Microbial degradation products of lurasidone and their significance in postmortem toxicology

“…Recently, in a study to investigate microbial degradation of lurasidone in postmortem blood, our research group found that LURA degraded in unpreserved ante-mortem whole blood inoculated with human feces when incubated at 37 C or stored at ambient temperature. 18 It was established that Clostridium perfringens and Bacteroides spp. dominated these specimens, with the former reported to dominate postmortem specimens 19,20 and the latter previously reported in postmortem blood.…”