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Quetiapine use is on the rise, leading to a corresponding increase in acute intoxications, some of which have fatal outcomes. When assessing whole-blood quetiapine concentrations during forensic autopsies, interpretations are primarily based on toxicity data from studies of serum concentrations. To our knowledge, there are only two previous studies that have attempted to establish the ratio between whole blood and serum quetiapine concentrations with limited populations and high variability of results. Paired specimens of whole blood and serum from 16 quetiapine users recruited from the Psychiatric Clinic, St. Olav University Hospital were analyzed using LC-MS-MS. Quetiapine concentrations in both matrices were determined and compared. The mean blood:serum ratio of quetiapine was 0.74 (standard deviation (SD) = 0.05, 95% confidence interval (CI) 0.71-0.76, P < 0.001), range 0.66-0.85. Simple linear regression showed strong linear correlation between quetiapine concentrations in the two matrices (B = 0.774, P > 0.001, r = 0.999). Our results imply that quetiapine occurs at lower concentrations within erythrocytes than in plasma. This is most likely due to a high degree of plasma protein binding. Other factors which may influence the distribution of quetiapine between these compartments are solubility, metabolism and passive or active efflux mechanisms. We did not observe any covariation between blood:serum ratios and serum concentrations. Quetiapine was consistently present at lower concentrations in whole blood than in serum. If so inclined to, a conversion factor of ∼0.7 may be considered for extrapolation of concentrations from serum to whole blood, at least in cases with therapeutic quetiapine concentration levels., (© The Author(s) 2024. Published by Oxford University Press.)

Central nervous system inflammation might play a role in patients with depressive disorders. This hypothesis is supported by studies reporting increased cerebrospinal fluid levels of the inflammatory markers interleukin (IL)-6, IL-8 and tumor necrosis factor alpha (TNF-α) in patients with ongoing depression. In this case-control study, we aimed to examine whether these findings also applied to depressed patients in a geriatric population . Cerebrospinal fluid cytokine analyses were performed on 15 patients (age >60 years) with depressive disorders and 45 age- and sex matched controls (patients with headache or idiopathic facial palsy). IL-6, IL-8, IL-10, TNF-α, monocyte chemoattractant protein-1 and transforming growth factor beta 1 were included in the statistical analyses. Patients with depression had significantly lower cerebrospinal fluid levels of IL-6 as compared to controls ( p = 0.014) in the univariate analysis. The finding was, however, no longer statistically significant after correction for age and body mass index ( p = 0.097). Overall, this study indicates that the cytokines included in this study are not significantly altered in geriatric patients with depression. Future studies exploring cerebrospinal fluid cytokine levels should include corrections for possible confounding factors., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Schou, Larsen, Stunes and Sæther.)