An unusual case of risperidone instability in a fatality presenting an analytical and interpretative challenge

Detection of new metabolites of risperidone in the solid tissues and body fluids obtained from two cadavers by high resolution tandem mass spectrometry

Risperidone (Ris) is a second-generation antipsychotic that belongs to the chemical class of benzisoxazole derivatives. 9-Hydroxy (9OH-) Ris is well known among the six reported metabolites of Ris and had been examined using not only blood but also other matrices, but the other five metabolites reported such as benzisoxazole ring-cleaved Ris (c-Ris) and c-9OH-Ris had been detected only in blood, urine and feces. In the present work, large peaks of c-Ris and c-9OH-Ris were detected in the liver, kidney, cerebrum, blood, pericardial fluid, bile and urine obtained from two cadavers. There is a potential that c-Ris and c-9OH-Ris will be good markers to prove Ris consumption in forensic toxicology cases. For example, the peak ratios of c-Ris against the parent Ris in the kidney and blood were as high as 3.9 and 3.6 in cadaver 1; and 7.0 and 7.9 in cadaver 2, respectively. In addition to the previously reported six metabolites, five new metabolites such as dehydrogenated-Ris, 7-keto-Ris and three benzisoxazole ring-cleaved metabolites were disclosed in the present work, and the pathways for the totally eleven metabolites detected in human solid tissues and body fluids have also been proposed, because such pathways were neither reported nor discussed previously.

In vitro degradation of ziprasidone in human whole blood

A systematic study was performed into the degradation of ziprasidone in simulated postmortem blood. Fifteen potential degradation products not previously reported in the literature were observed. Four resulted from degradation in human blood, whereas the remaining products resulted from reaction with solvents: four from alkaline degradation, four from reaction with acetaldehyde, and three from reaction with acetone. To identify possible degradation products, a liquid chromatograph-diode array detector (LC-DAD) and liquid chromatograph quadrupole-time-of-flight mass spectrometer (LC-QTOF-MS) operating in auto-MS/MS mode were used. It was indicated from red-shifted UV-Vis spectra, accurate mass data, mass fragmentation data, and a deuteration experiment that the site of ziprasidone degradation, in the in vitro blood experiments, was the methylene carbon of the oxindole moiety. The major in vitro blood degradation products were proposed to be E/Z isomers of 3-ethylidene-ziprasidone. Further, another in vitro degradation product in microbially inoculated blood specimens was proposed to be 3-ethyl-ziprasidone. 3-Ethylidene-ziprasidone was hypothesized to form from the reaction of ziprasidone with acetaldehyde derived from the ethanol used to spike ziprasidone into the in vitro blood experiments. Data from two postmortem investigations were available for retrospective reanalysis. Attempts were made to detect degradation products of ziprasidone, but none were found.

Microbial degradation products of lurasidone and their significance in postmortem toxicology

Recent research reported that lurasidone degrades in unpreserved ante-mortem human whole blood inoculated with microorganisms known to dominate postmortem blood specimens. In vitro degradation occurred at a similar rate to risperidone, known to degrade in authentic postmortem specimens until below analytical detection limits. To identify the lurasidone degradation products formed, an Agilent 6520 liquid chromatograph quadrupole-time-of-flight mass spectrometer (LC-QTOF-MS) operating in auto-MS/MS mode was used. Numerous degradation products not previously reported in prior in vitro or in vivo pharmacokinetic studies or forced degradation studies were detected. Accurate mass data, mass fragmentation data, acetylation experiments, and a proposed mechanism of degradation analogous to risperidone supports initial identification of the major degradation product as N-debenzisothiazole-lurasidone (calculated m/z [M + H]⁺  = 360.2646). A standard was unavailable to conclusively confirm this identification. Retrospective data analysis of postmortem cases involving lurasidone identified the presence of the major degradation product in four of six cases where lurasidone was also detected. This finding is significant for toxicology laboratories screening for this drug in postmortem casework. The major postmortem lurasidone degradation product has consequently been added to the LC-QTOF-MS drug screen at Forensic Science SA (FSSA) to indicate postmortem lurasidone degradation in authentic postmortem blood specimens and as a marker of lurasidone administration in the event lurasidone is degraded to concentrations below detection limits.

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

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, under- or over-estimation 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 non-inoculated controls. However, the 1,2-benzisothiazole antipsychotics, ziprasidone and lurasidone, were found to degrade at a rate comparable to the known labile control, risperidone. In longer experiments (seven to twelve 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.

Time- and Site-Dependent Postmortem Redistribution of Antidepressants and Neuroleptics in Blood and Alternative Matrices

Postmortem redistribution (PMR) leads to challenges in postmortem case interpretation. Particularly antidepressants and neuroleptics are expected to undergo PMR based on their physico-chemical properties. For the current study, time- and site-dependent PMR of 20 antidepressants and neuroleptics were investigated in humans (authentic cases); five of which are discussed in detail (citalopram, mirtazapine, quetiapine, risperidone and venlafaxine) along with two metabolites (9-OH-risperidone and O-desmethylvenlafaxine). Blood [femoral (pB) and heart blood (HB)] and tissue biopsy samples (lung, kidney, liver, spleen, thigh muscle and adipose tissue) were collected upon admission to the institute utilizing a computed tomography-guided sample collection workflow (t1). Approximately 24 h later (t2; mean 23 ± 9.3 h), samples from the same body regions were collected manually. Liquid chromatography-tandem mass spectrometry was used for quantification. Most antidepressants and neuroleptics showed significant time-dependent concentration changes indicating the occurrence of PMR. For the first time, two phases of redistribution in pB for quetiapine were proposed (concentration decreases in the early postmortem phase, followed by concentration increases) and contrasting existing literature, both concentration increases and decreases in pB overtime were observed for risperidone and 9-OH-risperidone. Venlafaxine and its metabolite only showed minimal concentration changes, while citalopram exhibited a trend for concentration increases and mirtazapine for concentration decreases in pB overtime. Based on time-dependent tissue data, passive diffusion processes along the muscle-to-pB, liver-to-HB and lung-to-HB concentration gradients could be proposed along with bacterial degradation. Overall, no case interpretation had to be adjusted, which suggests that PMR changes of antidepressants and neuroleptics do not seem to be relevant for forensic case interpretation within the 24 h period that was investigated. However, limitations of the current study (e.g., temperature-controlled storage of the bodies) could have led to an underestimation of occurring postmortem changes, hence, interpretation of postmortem results should always be conducted with care, considering PMR phenomena and inter-individual variability.

From gut dysbiosis to altered brain function and mental illness: mechanisms and pathways

The human body hosts an enormous abundance and diversity of microbes, which perform a range of essential and beneficial functions. Our appreciation of the importance of these microbial communities to many aspects of human physiology has grown dramatically in recent years. We know, for example, that animals raised in a germ-free environment exhibit substantially altered immune and metabolic function, while the disruption of commensal microbiota in humans is associated with the development of a growing number of diseases. Evidence is now emerging that, through interactions with the gut-brain axis, the bidirectional communication system between the central nervous system and the gastrointestinal tract, the gut microbiome can also influence neural development, cognition and behaviour, with recent evidence that changes in behaviour alter gut microbiota composition, while modifications of the microbiome can induce depressive-like behaviours. Although an association between enteropathy and certain psychiatric conditions has long been recognized, it now appears that gut microbes represent direct mediators of psychopathology. Here, we examine roles of gut microbiome in shaping brain development and neurological function, and the mechanisms by which it can contribute to mental illness. Further, we discuss how the insight provided by this new and exciting field of research can inform care and provide a basis for the design of novel, microbiota-targeted, therapies.