Plasma clozapine and norclozapine in relation to prescribed dose and other factors in patients aged <18 years: data from a therapeutic drug monitoring service, 1994-2010

Weight gain, gender, and antipsychotics: a disproportionality analysis of the FDA Adverse Event Reporting System database (FAERS)

INTRODUCTION

Side effects are a very important aspect of antipsychotic treatments. Weight gain is an important side effect that jeopardizes the uninterrupted therapy administration, especially in patients with psychiatric conditions. This case-non-case pharmacovigilance study aims at investigating in a real-world adverse event reporting system whether several antipsychotics increase the risk of weight gain reporting, and the differences among men and women as far as weight gain as a reported adverse event is concerned.

AREAS COVERED

Adverse event reports submitted to the FDA Adverse Event Reporting System of the Food and Drug Administration of the United States (FAERS) of 24 major antipsychotics were extracted, cleaned, and analyzed to determine which of these drugs were correlated with weight gain. The Reported Odds Ratio (ROR) and the adjusted Reported Odds Ratio (aROR) were calculated for each antipsychotic using logistic regression models. Demographics like age, gender, and concomitant insulin use were taken into consideration for each drug.

EXPERT OPINION

Women had a statistically significant increase in weight gain reporting compared to men, while the men's group was associated with a reduced weight gain reporting in every antipsychotics in the logistic regression analyses. Out of the 24 antipsychotics included in our analysis, Aripiprazole, Brexpiprazole, Olanzapine, and Haloperidol had statistically significantly more weight increase reporting compared to the others.

CYP-catalysed cycling of clozapine and clozapine-N-oxide promotes the generation of reactive oxygen species in vitro

Clozapine is an effective atypical antipsychotic indicated for treatment-resistant schizophrenia, but is under-prescribed due to the risk of severe adverse drug reactions such as myocarditis.A mechanistic understanding of clozapine cardiotoxicity remains elusive.This study aimed to investigate the contribution of selected CYP isoforms to cycling between clozapine and its major circulating metabolites, N-desmethylclozapine and clozapine-N-oxide, with the potential for reactive species production.CYP supersome™-based in vitro techniques were utilised to quantify specific enzyme activity associated with clozapine, clozapine-N-oxide and N-desmethylclozapine metabolism.The formation of reactive species within each incubation were quantified, and known intermediates detected.CYP3A4 predominately catalysed clozapine-N-oxide formation from clozapine and was associated with concentration-dependent reactive species production, whereas isoforms favouring the N-desmethylclozapine pathway (CYP2C19 and CYP1A2) did not produce reactive species.Extrahepatic isoforms CYP2J2 and CYP1B1 were also associated with the formation of clozapine-N-oxide and N-desmethylclozapine but did not favour one metabolic pathway over another.Unique to this investigation is that various CYP isoforms catalyse clozapine-N-oxide reduction to clozapine.This process was associated with the concentration-dependent formation of reactive species with CYP3A4, CYP1B1 and CYP1A1 that did not correlate with known reactive intermediates, implicating metabolite cycling and reactive oxygen species in the mechanism of clozapine-induced toxicity.

Clinical pharmacokinetics of antipsychotics in pediatric populations: a scoping review focusing on dosing regimen

INTRODUCTION

Achieving optimal clinical responses and minimizing side effects through precision dosing of antipsychotics in children and adolescents with psychiatric disorders remains a challenge. Identifying patient characteristics (covariates) that affect pharmacokinetics can inform more effective dosing strategies and ultimately improve patient outcomes. This review aims to provide greater insight into the impact of covariates on the clinical pharmacokinetics of antipsychotics in pediatric populations.

AREAS COVERED

A comprehensive literature search was conducted, and the main findings regarding the effects of the covariates on the pharmacokinetics of antipsychotics in children and adolescents are presented.

EXPERT OPINION

Our study highlights significant covariates, including age, sex, weight, CYP2D6 phenotype, co-medication, and smoking habits, which affect the pharmacokinetics of antipsychotics. However, the findings were generally limited by the small sample sizes of naturalistic, open-label, observational studies, and the homogeneous subgroups. Dosing based on weight and preemptive genotyping could prove beneficial for optimizing the dosing regimen in pediatric populations. Future research is needed to refine dosing recommendations and establish therapeutic reference ranges critical for precision dosing and Therapeutic Drug Monitoring (TDM). The integration of individual patient characteristics with TDM can further optimize the efficacy and safety of antipsychotics for each patient.

Impact of NFIB and CYP1A variants on clozapine serum concentration-A retrospective naturalistic cohort study on 526 patients with known smoking habits

Clinical response of clozapine is closely associated with serum concentration. Although tobacco smoking is the key environmental factor underlying interindividual variability in clozapine metabolism, recent genome-wide studies suggest that CYP1A and NFIB genetic variants may also be of significant importance, but their quantitative impact is unclear. We investigated the effects of the rs2472297 C>T (CYP1A) and rs28379954 T>C (NFIB) polymorphisms on serum concentrations in smokers and nonsmokers. The study retrospectively included 526 patients with known smoking habits (63.7% smokers) from a therapeutic drug monitoring service in Norway. Clozapine dose-adjusted concentrations (C/D) and patient proportions with subtherapeutic levels (<1070 nmol/L) were compared between CYP1A/NFIB variant allele carriers and homozygous wild-type carriers (noncarriers), in both smokers and nonsmokers. Clozapine C/D was reduced in patients carrying CYP1A-T and NFIB-C variants versus noncarriers, both among smokers (-48%; p < 0.0001) and nonsmokers (-35%; p = 0.028). Patients who smoke carrying CYP1A-T and NFIB-C variants had a 66% reduction in clozapine C/D versus nonsmoking noncarriers (p < 0.0001). The patient proportion with subtherapeutic levels was 2.9-fold higher in patients who smoke carrying NFIB-C and CYP1A-T variants versus nonsmoking noncarriers (p < 0.0001). In conclusion, CYP1A and NFIB variants have significant and additive impact on clozapine dose requirements for reaching target serum concentrations. Patients who smoke carrying the studied CYP1A and NFIB variants, comprising 2.5% of the study population, may need threefold higher doses to prevent risk of clozapine undertreatment. The results suggest that pre-emptive genotyping of NFIB and CYP1A may be utilized to guide clozapine dosing and improve clinical outcomes in patients with treatment-resistant schizophrenia.

Metabolic Effects of Clozapine Administration Based on Sex Differences and the Relationships Between Dosage and Prolactin Levels: An Observational Study

OBJECTIVE

Clozapine is the second-generation antipsychotic that induces the largest metabolic disorders. However, evidence is limited to the liabilities based on sex differences. This study aimed to investigate the effects of clozapine treatment on metabolic and neuroendocrine parameters, and the relationships between prescribed clozapine dosage and prolactin levels that may be associated with plasma clozapine concentrations, in 24 female and 24 male Japanese schizophrenia inpatients switched to clozapine.

METHODS

Within female and male subjects, sequential changes in 7 items of metabolic parameters, including anthropometric measurements, fasting serum lipid components and glucose levels, and estimated insulin resistance at 2 months were evaluated and analyzed against clozapine dosages and prolactin levels at 2 months.

RESULTS

Triglyceride levels, triglyceride to high-density lipoprotein ratios reflecting insulin resistance and glucose levels increased in female and male subjects. High-density lipoprotein cholesterol levels decreased in female and male subjects. High-density lipoprotein cholesterol levels were negatively correlated with prolactin levels in female subjects, and glucose levels were positively correlated with prolactin levels in male subjects, although clozapine doses showed no such correlations.

CONCLUSIONS

Clozapine administration developed sex-neutral metabolic disorders in the study subjects. Higher prolactin levels seemed to increase the risk of dyslipidemia and hyperglycemia with sex differences, which suggested that serum prolactin levels other than clozapine doses might be useful to predict sex-specific metabolic disorders. Further prospective studies, combining measurement of metabolic hormones and plasma concentrations of clozapine and its metabolites, will help to confirm our findings.

Clozapine and Norclozapine Plasma Levels in Patients Switched Between Different Liquid Formulations

BACKGROUND AND OBJECTIVE

Clozapine is the drug of choice for treatment-resistant schizophrenia. The primary objective of this study was to compare plasma clozapine and N-desmethylclozapine levels in patients switched between 2 liquid formulations [Denzapine suspension and clozapine oral solution (St George's ZTAS)]. Secondary objectives included comparison of safety, tolerability, and patient acceptability.

METHODS

This was a noninterventional, observational, prospective follow-up of patients consecutively switched between formulations of clozapine liquid in a large inner-city NHS mental health trust. The authors also performed retrospective analysis of outcomes from patient case notes.

RESULTS

The authors identified 43 patients receiving Denzapine suspension in the trust. Data were available for 43 patients switched from Denzapine to clozapine oral solution (St George's ZTAS), among whom, 15 (32%) were excluded from the analysis. Of the 28 patients for whom data were available, the 90% confidence interval for the ratio of mean values for corrected Cmin 91.5 (85.2%-98.4%) and uncorrected Cmin 91.2 (84.4%-98.6%) were within the guideline range of bioequivalence (80%-125%). Safety and tolerability profiles were comparable between the 2 formulations (P = 0.10). Patient acceptability was also similar between the brands in most domains. However, there was a taste preference for Denzapine suspension.

CONCLUSIONS

No significant difference in clozapine plasma levels was observed after switching from Denzapine suspension to a recently introduced clozapine solution. This study also highlights the significance of medicinal characteristics such as taste for patient acceptability and compliance.

Clozapine Metabolism is Associated With Absolute Neutrophil Count in Individuals With Treatment-Resistant Schizophrenia

Up to one-third of those with schizophrenia fail to respond to standard antipsychotics and are considered to have treatment-resistant schizophrenia, a condition for which clozapine is the only evidence-based medication. While up to 60% of treated individuals obtain therapeutic benefits from clozapine, it is currently underprescribed worldwide, partly because of concerns related to its broad adverse effect profile. In particular, the potential effects of clozapine on the immune system have gained relevance after a recent study showed that drug plasma concentrations were inversely correlated with neutrophil counts in individuals routinely undergoing treatment. Seeking to investigate this relationship in more detail, we extracted metabolic, immune, and genetic data from a UK cohort of long-term clozapine users linked to a clozapine monitoring service, CLOZUK2 (N = 208). Whilst a correlation analysis was compatible with the original results, a multiple linear regression accounting for dose and other confounding factors additionally allowed us to estimate the decrease in absolute neutrophil counts to approximately 141 cells/mm3 for every 0.1 mg/L increase in clozapine concentration. However, this association was attenuated after controlling for the metabolic ratio between clozapine and its main metabolite, norclozapine, which was itself negatively associated with neutrophil concentrations. Further analyses revealed that these relationships are likely moderated by genetic factors, as three pharmacogenomic SNPs previously associated to norclozapine plasma concentrations and the metabolic ratio (rs61750900, rs2011425 and rs1126545) were shown to be independently associated with a variation in neutrophil counts of about 400 cells/mm3 per effect allele. Such results are compatible with an effect of norclozapine, but not necessarily clozapine, on immune cell counts, and highlight the need for further investigations into the potential role of genetic determinants of clozapine pharmacokinetics in the occurrence of adverse effects during treatment.

Interest of Fluvoxamine as an Add-On to Clozapine in Children With Severe Psychiatric Disorder According to CYP Polymorphisms: Experience From a Case Series

Despite its drastic efficacy in resistant psychiatric disorders, clozapine remains rarely used in youth due to its side effects. Clozapine plasma level is determined through its metabolism involving several isoforms of cytochromes 450 (CYP450) family. Isoform CYP1A2 appears as a limiting enzyme involved in the metabolism of clozapine, while isoforms 2C19, 2D6, 3A4, and 3A5 also contribute in a minor way. Clozapine efficacy is limited by a significant inter-patient variability in exposure according to CYP's polymorphisms. Clozapine plasma levels may be increased with CYP inhibitors such as fluvoxamine. This drug is a potent enzymatic inhibitor of CYP1A2 and, to a lesser extent, of CYP3A4 and CYP2D6. Hence, in case of CYP's polymorphisms in youth, the use of fluvoxamine as add-on to clozapine could help in reaching clinical and biological efficacy and allowing lower clozapine dosage and a better tolerance profile as it has already been described in adults. We report four pediatric cases with severe psychiatric disorders underlying our experience with CYP polymorphism explorations and the use of fluvoxamine as add-on to clozapine. Our four patients clinically improved after the introduction of fluvoxamine, enhancing clozapine metabolism and therefore the clozapine plasma level within therapeutic range. Despite the interesting results of fluvoxamine, we report a severe issue of tolerance for one patient, emphasizing the need for caution regarding possible drug interactions when fluvoxamine is considered. Hence, we propose a detailed step-by-step multidisciplinary protocol.

Identification of a novel polymorphism associated with reduced clozapine concentration in schizophrenia patients-a genome-wide association study adjusting for smoking habits

Clozapine (CLZ) is the superior antipsychotic drug for treatment of schizophrenia, but exhibits an extensive interpatient pharmacokinetic variability. Here, we conducted a genome-wide association study (GWAS) of CLZ serum concentration adjusting for known smoking habits, which is a major nongenetic factor reducing CLZ levels. The study included 484 patients with 10,283 steady-state serum concentrations of CLZ and N-desmethylclozapine, prescribed dosing, co-medications and known smoking habits (n = 422; 9284 serum samples) from a therapeutic drug monitoring (TDM) service. The GWAS analyses were performed with and without smoking habits as covariate, where possible hits were assessed in relation to the target CLZ concentration range applied in the TDM service (300-2500 nmol/L). The smoking-independent analysis of N-desmethylclozapine serum concentration and the CLZ-to-N-desmethylclozapine ratio replicated the previously identified locus on chromosome 4. After adjusting for smoking habits in patients confirmed as 'smokers' (61%) or 'nonsmokers' (39%), a novel variant (rs28379954; minor T>C allele frequency 4.1%; 7.6% CT carriers in the population) within the gene encoding the nuclear factor 1 B-type (NFIB) was significantly associated with reduced CLZ serum concentration (p = 1.68 × 10-8, beta = -0.376; explained variance 7.63%). There was no significant association between rs28379954 and N-desmethylclozapine concentration in the GWAS analysis (p = 5.63 × 10-5). The fraction of CLZ TDM samples below 300 nmol/L was significantly higher in carriers vs. noncarriers of the rs28379954 minor C allele [12.0% (95% CI: 9.4-14.7) vs. 6.2% (95% CI: 5.7-6.8), p < 0.001]. We identified a novel variant in the NFIB gene associated with reduced CLZ levels and increased risk of subtherapeutic serum concentrations. This warrants testing of clinical relevance of screening for this gene variant, and also experimental studies to investigate the biological mechanisms of NFIB involvement in CLZ pharmacokinetics.

Understanding variability in the pharmacokinetics of atypical antipsychotics - focus on clozapine, olanzapine and aripiprazole population models

Antipsychotic medicines are widely used for the management of psychotic symptoms regardless of the underlying diagnosis. Most atypical antipsychotics undergo extensive metabolism prior to excretion. Various factors may influence their pharmacokinetics, particularly elimination, leading to highly variable drug concentrations between individual patients following the same dosing regimen. Population pharmacokinetic approach, based on nonlinear mixed effects modeling, is a useful tool to identify covariates explaining pharmacokinetic variability, as well as to characterize and distinguish unexplained residual and between-subject (interindividual) variability. In addition, this approach allows the use of both sparsely and intensively sampled data. In this paper, we reviewed the pharmacokinetic characteristics of clozapine, olanzapine and aripiprazole, focusing on a population modeling approach. In particular, models based on a nonlinear mixed effects approach performed by NONMEM^® software in order to identify and quantify sources of pharmacokinetic variability are presented. Population models were identified through systematic searches of PubMed and sixteen studies were selected. Some of the factors identified that significantly contribute to variability in elimination among clozapine, olanzapine, and aripiprazole are demographic characteristics, body weight, genetic polymorphism, smoking and in some cases drug interactions. Scientific research based on pharmacometric modeling is useful to further characterize sources of variability and their combined effect.

Evidence-based guidelines for the pharmacological treatment of schizophrenia: Updated recommendations from the British Association for Psychopharmacology

These updated guidelines from the British Association for Psychopharmacology replace the original version published in 2011. They address the scope and targets of pharmacological treatment for schizophrenia. A consensus meeting was held in 2017, involving experts in schizophrenia and its treatment. They were asked to review key areas and consider the strength of the evidence on the risk-benefit balance of pharmacological interventions and the clinical implications, with an emphasis on meta-analyses, systematic reviews and randomised controlled trials where available, plus updates on current clinical practice. The guidelines cover the pharmacological management and treatment of schizophrenia across the various stages of the illness, including first-episode, relapse prevention, and illness that has proved refractory to standard treatment. It is hoped that the practice recommendations presented will support clinical decision making for practitioners, serve as a source of information for patients and carers, and inform quality improvement.

A systematic review of sex-based differences in effectiveness and adverse effects of clozapine

Clozapine is one of the most widely used antipsychotics for treating psychiatric illnesses such as schizophrenia and bipolar disorder. This drug, however, is associated with adverse effects such as weight gain, metabolic syndrome, and blood dyscrasias. The manifestations of mental illness may differ between men and women. Yet, there is little evidence on the influence of sex on treatment response or the occurrence of AEs. To fill this gap of knowledge, we carried out a systematic review of the literature on sex differences in the effectiveness and adverse effects of clozapine. Scant evidence has been published on differences in effectiveness of clozapine between men and women. Indeed, to the best of our knowledge, this issue has only been addressed in a published study. Regarding adverse effects, males have been reported to be more likely to develop metabolic abnormalities such as cholesterol or triglycerides, hypertension, and cardiovascular risk, while females are at a higher risk for gaining weight, developing diabetes, and needing laxatives. Nevertheless, given the scarcity of sex-based studies on this drug, further studies are needed to explore sex-based differences, as the results obtained may be crucial to clinical practice and help improve the quality of life of patients.

Pharmacogenomic Variants and Drug Interactions Identified Through the Genetic Analysis of Clozapine Metabolism

OBJECTIVE

Clozapine is the only effective medication for treatment-resistant schizophrenia, but its worldwide use is still limited because of its complex titration protocols. While the discovery of pharmacogenomic variants of clozapine metabolism may improve clinical management, no robust findings have yet been reported. This study is the first to adopt the framework of genome-wide association studies (GWASs) to discover genetic markers of clozapine plasma concentrations in a large sample of patients with treatment-resistant schizophrenia.

METHODS

The authors used mixed-model regression to combine data from multiple assays of clozapine metabolite plasma concentrations from a clozapine monitoring service and carried out a genome-wide analysis of clozapine, norclozapine, and their ratio on 10,353 assays from 2,989 individuals. These analyses were adjusted for demographic factors known to influence clozapine metabolism, although it was not possible to adjust for all potential mediators given the available data. GWAS results were used to pinpoint specific enzymes and metabolic pathways and compounds that might interact with clozapine pharmacokinetics.

RESULTS

The authors identified four distinct genome-wide significant loci that harbor common variants affecting the metabolism of clozapine or its metabolites. Detailed examination pointed to coding and regulatory variants at several CYP* and UGT* genes as well as corroborative evidence for interactions between the metabolism of clozapine, coffee, and tobacco. Individual effects of single single-nucleotide polymorphisms (SNPs) fine-mapped from these loci were large, such as the minor allele of rs2472297, which was associated with a reduction in clozapine concentrations roughly equivalent to a decrease of 50 mg/day in clozapine dosage. On their own, these single SNPs explained from 1.15% to 9.48% of the variance in the plasma concentration data.

CONCLUSIONS

Common genetic variants with large effects on clozapine metabolism exist and can be found via genome-wide approaches. Their identification opens the way for clinical studies assessing the use of pharmacogenomics in the clinical management of patients with treatment-resistant schizophrenia.

Intra-individual variation of clozapine and norclozapine plasma levels in clinical practice

INTRODUCTION

Clozapine plasma levels are useful to monitor drug compliance, and also to assess and to prevent some side effects. Recently, routine monitoring to all clozapine-treated patients has been proposed to prevent relapses. However, high intra-individual variability in plasma levels has been reported too, although these studies have some limitations.

METHODS

We analysed differences between 2clozapine plasma levels separated by at least one year in a subgroup of 28 outpatients (82% male, mean age 47.9 years-old) with diagnosis of non-affective psychosis in clinical remission whose clozapine doses and smoking habits remained unchanged.

RESULTS

We found a non-significant increase in clozapine plasma levels [.30mg/L (SD=.14) vs. .32 (SD=.17); t=-.858, p=.40] and a significant decrease in norclozapine plasma levels [.27 (SD=.11) vs. .22 (SD=.10); t=3.27; p=.003]. Absolute coefficient of variation (CV) between first and second assessment were calculated. Forty-six and fifty-seven percent of cases had CV 20% in clozapine and norclozapine, respectively. CV of 50% was seen in 20.7% and 13.8% of clozapine and norclozapine test respectively. We discussed potential causes of such high CV.

CONCLUSIONS

Our study suggest high intra-individual variation even in a subgroup of very stable patients, which suggest that routine monitoring of these levels may be indicated in order to detect significant plasma variations. We think that clinicians should act with caution in case of a sudden decrease in plasma level. In the absence of obvious symptom severity variation, sources of intra-individual fluctuations might be considered first, before assuming poor compliance.

The Effect of Body Weight Changes on Total Plasma Clozapine Concentrations Determined by Applying a Statistical Model to the Data From a Double-Blind Trial

PURPOSE/BACKGROUND

Some therapeutic drug monitoring studies suggest that increased weight is associated with small increases in clozapine concentrations. The goal of this study was to reanalyze a US double-blind study using a sophisticated statistical model to test whether weight gains from baseline or increases in percentage of body fat from baseline, computed from a published equation, are associated with increased total plasma clozapine concentrations after controlling for the effects of smoking and sex.

METHODS/PROCEDURES

Using data from a multidosage randomized double-blind US clozapine trial previously published, a random intercept linear model of steady-state total plasma clozapine concentrations was fitted to 424 concentrations from 47 patients.

FINDINGS/RESULTS

After adjusting for sex and smoking, (1) a 1-kg gain in body weight during clozapine treatment was significantly associated with a 1.4% increase in total plasma clozapine concentrations (95% confidence interval = 0.55 to 2.3) and (2) a 1-point increase in percentage of body fat during clozapine treatment was significantly associated with a 5.4% increase in total clozapine concentration (2.5 to 8.3) in females and 1.4% (-1.1 to 4.0) in males.

IMPLICATIONS/CONCLUSIONS

As hypothesized, weight increases during clozapine treatment, which probably reflect increases in fat tissue, were associated with increases in total plasma concentrations. Pending further replication in other samples, it seems likely that clozapine may deposit in body fat and that this may decrease clozapine clearance. This change may be small in most patients but may be clinically relevant in females with major gains in body fat.

Combination of Electroconvulsive Therapy and Clozapine in Treatment-Resistant Schizophrenia

OBJECTIVE

This study aimed to investigate the effectiveness and tolerability of the combination of electroconvulsive therapy (ECT) in patients with clozapine-treated schizophrenia.

METHODS

Patients with clozapine-treated schizophrenia during five years of pre-determined period were recruited from Electronic Medical Record. Clinical effects of acute ECT on psychotic symptoms were investigated. We also tried to identify predictive variables requiring maintenance treatment of ECT.

RESULTS

Fourteen patients received ECT and clozapine and sixteen were treated with clozapine alone. In the ECT group, which could be refined as clozapine-resistance, PANSS total score was significantly reduced by 19.0±9.9 points, corresponding to a reduction rate of 18.5±8.3%. The clinical remission defined as 20% PANSS reduction criteria was achieved at 42.9%. The subscale factors were significantly reduced, among which the negative symptom was the least. There was no difference in demographic and clinical information between patients receiving and not receiving maintenance ECT, and not all patients seemed to need maintenance ECT if clozapine is continued.

CONCLUSION

Combination of ECT and clozapine in patients with clozapine-resistant schizophrenia resulted in a rapid and substantial reduction of psychotic symptoms. Further studies are needed to improve the effectiveness and tolerability of ECT.

Reliable clinical serum analysis with reusable electrochemical sensor: Toward point-of-care measurement of the antipsychotic medication clozapine

Clozapine is one of the most promising medications for managing schizophrenia but it is under-utilized because of the challenges of maintaining serum levels in a safe therapeutic range (1-3μM). Timely measurement of serum clozapine levels has been identified as a barrier to the broader use of clozapine, which is however challenging due to the complexity of serum samples. We demonstrate a robust and reusable electrochemical sensor with graphene-chitosan composite for rapidly measuring serum levels of clozapine. Our electrochemical measurements in clinical serum from clozapine-treated and clozapine-untreated schizophrenia groups are well correlated to centralized laboratory analysis for the readily detected uric acid and for the clozapine which is present at 100-fold lower concentration. The benefits of our electrochemical measurement approach for serum clozapine monitoring are: (i) rapid measurement (≈20min) without serum pretreatment; (ii) appropriate selectivity and sensitivity (limit of detection 0.7μM); (iii) reusability of an electrode over several weeks; and (iv) rapid reliability testing to detect common error-causing problems. This simple and rapid electrochemical approach for serum clozapine measurements should provide clinicians with the timely point-of-care information required to adjust dosages and personalize the management of schizophrenia.

Quantification of the steady-state plasma concentrations of clozapine and N-desmethylclozapine in Japanese patients with schizophrenia using a novel HPLC method and the effects of CYPs and ABC transporters polymorphisms

Background This study developed a novel high-performance liquid chromatography (HPLC) method for the simultaneous quantification of clozapine and its active metabolite, N-desmethylclozapine, in human plasma and investigated the effects of various factors, including genetic polymorphisms in cytochrome P450 (CYP) 2D6, CYP3A5, ABCB1 and ABCG2, on the steady-state plasma trough concentrations (C₀) of clozapine and N-desmethylclozapine in Japanese patients with schizophrenia. Methods Forty-five patients had been receiving fixed doses of clozapine for at least four weeks. The CYP2D6 ( CYP2D6*2, CYP2D6*5, CYP2D6*10), CYP3A5 ( CYP3A5*3), ABCB1 (1236C > T, 2677G > T/A, 3435C > T) and ABCG2 (421 C > A) genotypes were identified by polymerase chain reaction. Results The within- and between-day coefficients of variation (CV) were less than 11.0%, and accuracy was within 9.0% over the linear range from 10 to 2500 ng/mL for both analytes, and their LOQs were each 10 ng/mL. The median C₀/dose (C₀/D) ratios of clozapine were significantly higher in patients with the ABCG2 421 A allele than in those with the 421 C/C genotype ( P = 0.010). However, there were no significant differences in C₀/D ratios of clozapine and N-desmethylclozapine among ABCB1, CYP2D6 or CYP3A5 genotypes. In multiple regression analysis, including polymorphisms, age, body weight and biochemical data of patients, the ABCG2 polymorphism alone was correlated with the C₀/D ratios of clozapine ( R²= 0.139, P = 0.016). Conclusions Among the various CYPs and drug transporters, BCRP appeared to most strongly influence clozapine exposure. Knowledge of the patient's ABCG2 421 C > A genotype before initiating therapy may be useful when making dosing decisions aimed at achieving optimal clozapine exposure.

Fusing Sensor Paradigms to Acquire Chemical Information: An Integrative Role for Smart Biopolymeric Hydrogels

The Information Age transformed our lives but it has had surprisingly little impact on the way chemical information (e.g., from our biological world) is acquired, analyzed and communicated. Sensor systems are poised to change this situation by providing rapid access to chemical information. This access will be enabled by technological advances from various fields: biology enables the synthesis, design and discovery of molecular recognition elements as well as the generation of cell-based signal processors; physics and chemistry are providing nano-components that facilitate the transmission and transduction of signals rich with chemical information; microfabrication is yielding sensors capable of receiving these signals through various modalities; and signal processing analysis enhances the extraction of chemical information. The authors contend that integral to the development of functional sensor systems will be materials that (i) enable the integrative and hierarchical assembly of various sensing components (for chemical recognition and signal transduction) and (ii) facilitate meaningful communication across modalities. It is suggested that stimuli-responsive self-assembling biopolymers can perform such integrative functions, and redox provides modality-spanning communication capabilities. Recent progress toward the development of electrochemical sensors to manage schizophrenia is used to illustrate the opportunities and challenges for enlisting sensors for chemical information processing.

Relationship between clozapine dose, serum concentration, and clinical outcome in children and adolescents in clinical practice

Information on dose- and concentration-related clinical effects of clozapine treatment in children and adolescents is scarce. This study aimed to examine the relationship between dose, serum concentration, and clinical outcome as well as the influencing factors thereof in paediatric patients treated with clozapine. Data from a routine Therapeutic Drug Monitoring (TDM) service between 2004 and 2014 were studied in 68 patients, aged 11-18 years. Severity of illness, therapeutic effectiveness and adverse drug reactions (ADRs) were assessed by standardized means. A relationship between the daily dose (mean 319 mg, 4.9 mg/kg) and serum concentration (mean 387 ng/ml) of clozapine was found with the variation in dose explaining 30 % of the variability in clozapine serum concentrations. Also gender contributed to the variability, however, no influence of age or concomitant medications was detected. Furthermore, a significant association was found between clozapine serum concentration and the occurrence of ADRs. Patients without ADRs had a lower mean serum concentration than those with mild (261.4 vs 407.3 ng/ml, P = 0.018) and moderate ADRs (261.4 vs 416.3 ng/ml, P = 0.028). As clozapine was estimated to be effective in lower blood concentrations, guidance on a possibly lower therapeutic range of clozapine serum levels in paediatric patients is provided. With ADRs increasing under higher concentrations, TDM is strongly recommended in paediatric clozapine therapy for individualized dosing. Dose adjustment in females also might be reasonable according to gender-related differences in serum concentrations. However, regarding the limitations of this study results should be validated in larger studies with more standardized designs.

Practical pharmacotherapy in child psychiatry: an update

Psychopharmacology is an increasingly important aspect of child and adolescent psychiatry. The evidence base for the psychopharmacological treatment of depression, anxiety, schizophrenia, bipolar disorder, obsessive—compulsive disorder (OCD) and attention-deficit hyperactivity disorder (ADHD) is increasing. This article presents a synthesis of the information from randomised controlled trials, meta-analyses and the UK NICE guidelines as an aid to practical psychopharmacology.

[Pharmacovigilance in child and adolescent psychiatry]

Rational pharmacotherapy is a challenging task in child and adolescent psychiatry. Increasing prescription numbers contrast with the uncertainties of safety and efficacy issues. The lack of clinical (authorization) trials often implies a non- age-specific use of drugs. However, young patients show particular metabolic conditions and a higher vulnerability for adverse drug reactions. Thus it seems mandatory to create age-specific pharmacological data about efficacy and safety of psychotropic drug use in minors. Legislation authorities became aware of this situation and introduced European and national scientific pharmacovigilance regulations and programmes accordingly in order to continuously evaluate the benefit-risk-ratio, detect, collect, minimize, and prevent adverse effects of drugs by appropriate measures, e.g., therapeutic drug monitoring. In this paper the principles and needs of pharmacovigilance in child and adolescent psychiatry are discussed. Furthermore a large multicenter clinical trial («TDM-VIGIL»), funded by the German Federal Institute for Drugs and Medical Devices, is presented, which appeals to collect epidemiological prescription and safety data of psychotropic drugs in children and adolescents using an internet-based data infrastructure (patient registry).

Therapeutic drug levels of second generation antipsychotics in youth: a systematic review

OBJECTIVE

In children and adolescents, the prevalence rate of mental illness is claimed to be as high as 10-20%. Effective pharmacological treatments are available for use in children, adolescents, and adults; however, most of what is known about the effects of these treatments has been confirmed in clinical studies involving adults only. Second generation antipsychotic drugs (SGAs) are the most common class of antipsychotic medication used in pediatric populations, and these drugs are increasingly being used for disorders other than psychosis. Many SGAs are routinely used in pediatric care, and the vast majority of use in this population is off label. Children, adolescents, and adults differ in age, weight, height, and metabolism, which may lead to pharmacokinetic differences in how drugs ultimately affect target tissues. The aim of this review is to summarize and evaluate the literature that investigated blood plasma levels of SGAs in youth.

METHODS

Plasma levels were assessed in relation to their administered dose, indication, and therapeutic range (if known). Studies were limited to those evaluating oral administration only. A systematic electronic database search for peer-reviewed articles published between 2000 and 2013 was conducted. Twenty-one articles were included in the review. Additional articles for discussion were also included throughout the article.

RESULTS

The only SGA that may require routine therapeutic drug monitoring (TDM) in youth given the current body of research is clozapine. Highly variable results were seen in studies of aripiprazole, olanzapine, and risperidone, indicating that more research is needed on plasma levels with these drugs. Quetiapine maintained a similar profile to that found in adults, with no dosage adjustments or indications of TDM.

CONCLUSION

TDM may be indicated in any circumstance in which cytochrome P450 inhibitors or inducers are coprescribed. Further research is required for establishing a sounder safety profile for SGA use in the pediatric population.

Systematic review of the efficacy and tolerability of clozapine in the treatment of youth with early onset schizophrenia

BACKGROUND

The use of clozapine (CLZ) for treatment-resistant schizophrenia is well established in adults. However, it is seldom used in youth with early onset schizophrenia (EOS) largely because of lack of clarity about its risk benefit ratio. This review synthesises and evaluates available evidence regarding the efficacy and tolerability of CLZ in EOS with the aim to assist clinical decision-making.

METHODS

We conducted a systematic review of the primary literature on the clinical efficacy and adverse drug reactions (ADRs) observed during CLZ treatment in EOS. We also identified relevant practice guidelines and summarised current guidance.

RESULTS

CLZ showed superior efficacy than other antipsychotics in treating refractory EOS patients; short-term clinical trials suggest an average improvement of 69% on the Brief Psychiatric Rating Scale that was sustained during long-term follow-up (up to 9 years). No fatalities linked to CLZ treatment were reported. Sedation and hypersalivation were the most common complaints, reported by over 90% of patients. Other common ADRs (reported in 10-60% of patients) were enuresis, constipation, weight gain, and non-specific EEG changes. Less common ADRs (reported in 10-30% of patients) were akathisia, tachycardia and changes in blood pressure. Neutropenia was reported in 6-15% of cases but was usually transient while agranulocytosis was rare (<0.1%). Seizures were also uncommon (<3%). Metabolic changes were relatively common (8-22%) but emergent diabetes was not frequently observed (<6%). Overall the rate of discontinuation was low (3-6%). Current guidelines recommend the use of CLZ in EOS patients who have failed to respond to two adequate trials with different antipsychotics and provide detailed schedules of assessments to evaluate and assess potential ADRs both prior to initiation and throughout CLZ treatment.

CONCLUSION

Available data although limited in terms of number of studies are consistent in demonstrating that CLZ is effective and generally safe in the treatment of refractory EOS provided patients are regularly monitored.

Clinician hesitation prior to clozapine initiation: is it justifiable?

Clozapine has been endorsed by national clinical guidelines for 10 years and yet underutilisation and delay to initiation remain rife. Although there will be good clinical reasons for clozapine not being initiated for some patients, it is hypothesised here that for others, clinicians' attitudes and preferences are the most likely predictive factors.