Quetiapine and Norquetiapine Serum Concentrations and Clinical Effects in Depressed Patients Under Augmentation Therapy With Quetiapine

Quetiapine-Related Deaths: In Search of a Surrogate Endpoint

Quetiapine is a second-generation antipsychotic drug available for two and half decades. Due to increased misuse, prescription outside the approved indications, and availability on the black market, it is being encountered in medicolegal autopsies more frequently. For instance, it has been linked to increased mortality rates, most likely due to its adverse effects on the cardiovascular system. Its pharmacokinetic features and significant postmortem redistribution challenge traditional sampling in forensic toxicology. Therefore, a systematic literature review was performed, inclusive of PubMed, the Web of Science-core collection, and the Scopus databases; articles were screened for the terms "quetiapine", "death", and "autopsy" to reevaluate each matrix used as a surrogate endpoint in the forensic toxicology of quetiapine-related deaths. Ultimately, this review considers the results of five studies that were well presented (more than two matrices, data available for all analyses, for instance). The highest quetiapine concentrations were usually measured in the liver tissue. As interpreted by their authors, the results of the considered studies showed a strong correlation between some matrices, but, unfortunately, the studies presented models with poor goodness of fit. The distribution of quetiapine in distinct body compartments/tissues showed no statistically significant relationship with the length of the postmortem interval. Furthermore, this study did not confirm the anecdotal correlation of peripheral blood concentrations with skeletal muscle concentrations. Otherwise, there was no consistency regarding selecting an endpoint for analysis.

Insights into the population pharmacokinetics and pharmacodynamics of quetiapine: a systematic review

INTRODUCTION

Quetiapine exhibits notable pharmacokinetic and pharmacodynamic (PK/PD) variability, the origins of which are poorly understood. This systematic review summarizes published population PK/PD studies and identifies significant covariates accounting for this variability to inform precision dosing.

METHODS

We systematically searched the PubMed, Web of Science, and Embase databases and compared study characteristics, model parameters, and covariate effects. Visual predictive distributions were used to compare different models. Forest plots and Monte Carlo simulations were used to assess the influence of covariates.

RESULTS

Six population PK and three population PK/PD studies were included. The median apparent clearance in adults was 87.7 L/h. Strong and moderate cytochrome P450 3A4 inducers increased the apparent clearance approximately fourfold, while strong cytochrome P450 3A4 inhibitors reduced it by 93%. The half-maximum effect concentrations were 82.8 ng/mL for the Brief Psychiatric Rating Scale and 583 ng/mL for dopamine D2 receptor occupancy. Both treatment duration and quetiapine exposure were associated with weight gain.

CONCLUSIONS

Concurrent administration of potent or moderate CYP3A4 inducers and inhibitors need to be avoided in quetiapine-treated patients. When co-medication is required, it is recommended to adjust the dosage based on therapeutic drug monitoring. Additional research is warranted to delineate the dose-exposure-response relationships of quetiapine and active metabolite norquetiapine in pediatrics, geriatrics, hepatically-impaired patients, and women using contraceptives or are pregnant or menopausal.

PROSPERO REGISTRATION

CRD42023446654.

Post-therapy plasma concentrations of quetiapine in Taiwanese patients

AIMS

Quetiapine is widely used to treat psychiatric disorders such as major depression, generalized anxiety disorder, dysthymic disorder, and insomnia other than schizophrenia and bipolar disorder. This study investigated the diagnostic distribution of quetiapine use in patients in a psychiatric hospital, the doses of quetiapine prescribed, and the plasma concentrations (Cps) of quetiapine and active metabolites.

METHODS

We enrolled 107 patients who had been prescribed quetiapine for at least 4 weeks. Diagnoses, demographics, and concomitant medications were recorded. Blood sampling was performed in the morning, approximately 12 h after the before-bed dose of quetiapine.

RESULTS

Diagnoses comprised schizophrenia (n = 25), bipolar disorder (n = 51), major depression (n = 15), dysthymic disorder (n = 9), and others (n = 7). The daily dose (DD) of quetiapine ranged from 25 to 800 (175.9 ± 184.4) mg, with the mean Cp being 105.6 ± 215.3 ng/ml, with a mean Cps/DD ratio of 0.58 ± 0.55 ng/ml/mg. There was a moderate positive linear correlation between the dose and Cps of quetiapine (r = 0.60), and the interpatient variation in Cps/DD ratio was up to 26-fold.

CONCLUSION

Quetiapine is used in various doses to treat many psychiatric disorders other than psychosis, and it is usually prescribed as a secondary antipsychotic for symptoms such as insomnia or agitation. A wide interpatient variation of the Cps/DD ratio was noticed. Patients of East Asian descent may exhibit a 50% to 100% increase in the Cps/DD ratio for quetiapine compared with patients of Western descent.

[Therapeutic drug monitoring of antipsychotic drugs in routine psychiatric practice]

OBJECTIVE

To evaluate the relationship between daily doses of antipsychotic drugs, their serum concentrations, and characteristics of patients treated for schizophrenia or schizophreniform disorder in day-to-day clinical practice.

MATERIAL AND METHODS

A total of 187 patients were included in the study, 77 (41.1%) patients were on monotherapy, and 110 (58.9%) patients received two or more antipsychotics. Patients age was 27.8±8.1 years, and their body weight was 79.8±15.6 kg. The sample was represented mainly by young men (93.0%). The proportion of smokers was 37.4%. The appropriate HPLC-MS/MS method was used for the simultaneous analysis of 8 antipsychotics and its active metabolites. Serum concentrations of the drugs aripiprazole (ARI), chlorpromazine (CPZ), haloperidol (HAL), zuclopenthixol (ZUC), clozapine (CLO), risperidone (RIS), quetiapine (QUE), olanzapine (OLA), norclozapine (N-desmethylclozapine, NOR), 9-hydroxyrisperidone (9-OH-RIS), dehydroaripiprazole (DGA) were measured. The serum concentration/dose ratio (C/D) was employed as the primary outcome measure, as doses were not kept constant during the study. The active antipsychotic fraction (drug+active metabolite, active moiety - AM) was also evaluated for RIS and ARI. In addition, the metabolite/parent ratio (MPR) was evaluated for RIS and ARI.

RESULTS

A total of 265 biological samples were obtained, 421 and 203 measurements of the concentration of drugs and their metabolites were carried out, respectively. Overall, 48% of antipsychotics levels were in the expected therapeutic ranges, 30% were below therapeutic ranges, and 22% were above them. A total of 55 patients underwent dose adjustments or drug changes due to ineffectiveness or side-effects. It has been found that smoking reduces the level of C/D for CLO (p<0.01, Mann-Whitney test). We have established that comedication with CLO significantly increases the C/D ratio of QUE (p<0.05, Mann-Whitney test). We have not revealed any influence of weight and age of the subjects on the C/D. The dose-concentration regression relationships are formalized for all AP.

CONCLUSION

Therapeutical drug monitoring (TDM) is an essential tool to personalize antipsychotic therapy. Careful analysis of TDM data can contribute significantly to the study of the impact of individual patient characteristics on systemic exposure to these drugs.

Inflammation and psychotropic drugs: the relationship between C-reactive protein and antipsychotic drug levels

RATIONALE

In psychiatric clinical practice, there is a need to identify psychotropic drugs whose metabolisms are prone to be altered with increased inflammatory activity in an individual patient.

OBJECTIVES

The aim of this study was to find out whether elevated serum levels (≥5 mg/l) of C-reactive protein (CRP), an established laboratory marker of infection and inflammation, are associated with increased serum concentrations of the atypical antipsychotic drugs clozapine, quetiapine, and risperidone.

METHODS

Therapeutic drug monitoring request forms of patients whose antipsychotic drug concentrations had been measured under conditions of normal (<5 mg/l) and pathological (>5 mg/l) levels of C-reactive protein were retrospectively screened. The serum concentrations in relation to the daily doses [concentration per dose (C/D) (ng/mL/mg)] and the metabolic ratios [ratio of concentrations (metabolite/drug)] were compared intraindividually by the Wilcoxon signed rank test. To the study effects of the intensity of infections on drug concentrations, C-reactive protein and C/D levels were submitted to Spearman's correlation analysis.

RESULTS

Elevated levels of C-reactive protein were found in 105 patients. They were significantly associated with elevated values in C/D for clozapine (n = 33, P < 0.01) and risperidone (n = 40, P < 0.01). A trend for an increase was found for quetiapine (n = 32, P = 0.05). Median increases were 48.0 % (clozapine), 11.9 % (quetiapine), and 24.2 % (active moiety of risperidone), respectively.

CONCLUSIONS

In patients who exhibit signs of inflammation or infection with increased C-reactive protein values during psychopharmacological treatment, especially under clozapine and risperidone, therapeutic drug monitoring is recommendable in order to minimize the risk of intoxications due to elevated drug concentrations.