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-MSMS. Quetiapine concentrations in both matrices were determined and compared. The mean blood:serum ratio of quetiapine was 0.74 (SD = 0.05, 95% 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 approximately 0.7 may be considered for extrapolation of concentrations from serum to whole blood, at least in cases with therapeutic quetiapine concentration levels.

中文翻译：

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治疗药物监测标本中喹硫平在血清和全血中的分布

喹硫平的使用量不断增加，导致急性中毒事件相应增加，其中一些会造成致命后果。在法医尸检期间评估全血喹硫平浓度时，解释主要基于血清浓度研究的毒性数据。据我们所知，之前只有两项研究试图确定全血和血清喹硫平浓度之间的比率，但人群有限且结果变异性很大。使用 LC-MSMS 对从圣奥拉夫大学医院精神病诊所招募的 16 名喹硫平使用者的全血和血清配对样本进行了分析。测定并比较了两种基质中的喹硫平浓度。喹硫平的平均血液：血清比为0.74（SD = 0.05，95% CI 0.71-0.76，p＜0.001），范围0.66-0.85。简单线性回归显示两种基质中喹硫平浓度之间的强线性相关性(B＝0.774，p＞0.001，r＝0.999)。我们的结果表明喹硫平在红细胞内的浓度低于血浆中的浓度。这很可能是由于血浆蛋白的高度结合所致。可能影响喹硫平在这些区室之间分布的其他因素是溶解度、代谢和被动或主动外排机制。我们没有观察到血液：血清比率和血清浓度之间存在任何协变。全血中喹硫平的浓度始终低于血清中的浓度。如果愿意，可以考虑使用大约 0.7 的转换因子来外推血清到全血的浓度，至少在具有治疗性喹硫平浓度水平的情况下是如此。