Clozapine pharmacokinetics in children and adolescents with childhood-onset schizophrenia

Clozapine Treatment for Aggressive Behaviors in Youths with Neurodevelopmental Disorders

Objectives: The aim of this study was to assess effectiveness and tolerability of Clozapine in the treatment of aggression in youth with Neurodevelopmental Disorders. Methods: Patients were consecutively admitted at our third-level university hospital with nationwide catchment from June 2018 to October 2022, and followed up to July 2023. Eligibility criteria were as follows: (1) Autism Spectrum Disorder (ASD) and/or Intellectual Disability/Borderline Cognitive Functioning, (2) behavioral dyscontrol with physical aggression; (3) age range between 8 and 18 years; (4) clinical indication for Clozapine treatment after at least two failed trials with other Second-Generation Antipsychotics (SGAs); (5) availability of an at least 6-month-long follow-up. To evaluate the response to Clozapine, we used the Clinical Global Impressions (CGI) rating scales (Clinical Global Impressions-Severity [CGI-S] and Clinical Global Impressions-Improvement [CGI-I]), the Children's Global Assessment Scale (CGAS), and the Aberrant Behavior Checklist (ABC). Results: Twenty-six children and adolescents (21 boys, age 13.47 ± 2.05 years, follow-up duration 9.77 ± 3.50 months) were included in the analysis. Clinical severity (CGI-S) and functional impairment (Clinical Global Assessment Scale) significantly improved, as well as the ABC Total Score and the scores in several subscales. Sixteen patients (61.54%) were responders (CGI-I ≤2), and 13 (50.00%) displayed remission of aberrant behaviors (ΔABC-Total >35), while response/remission condition was not affected by add-on medications and psychotherapy. Most frequent side effects were increased appetite (50.00%), sialorrhea (38.46%), and increased repetitive behaviors (26.92%). Two patients presented epileptic seizures, while no patients presented leucopoenia. Conclusions: Our results suggest that Clozapine may be helpful in ameliorating treatment-resistant aggression in youth with neurodevelopmental conditions. Possible pharmacological strategies for the management of most frequent side effects are also suggested.

Delusions of Vampirism in an Adolescent and Treatment With Clozapine: A Case Report

This case describes delusions of vampirism among several other psychotic symptoms in a 15-year-old who has a diagnosis of schizophrenia, with these delusions first presenting when he was 13 years of age. Delusions of vampirism can be associated with a strong desire to suck human blood but these delusional beliefs were not acted upon here. This is the first report of delusions of vampirism in childhood to date. The introduction of the antipsychotic medication clozapine after failed treatment trials with two other antipsychotic agents has been associated with a significant amelioration in symptomatology and an improvement in functioning.

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.

Adverse Drug Reactions in Relation to Clozapine Plasma Levels: A Systematic Review

Clozapine is the gold standard for treatment-resistant schizophrenia. Serious and even life-threatening adverse effects, mostly granulocytopenia, myocarditis, and constipation, are of great clinical concern and constitute a barrier to prescribing clozapine, thus depriving many eligible patients of a lifesaving treatment option. Interestingly, clozapine presents variable pharmacokinetics affected by numerous parameters, leading to significant inter- and intra-individual variation. Therefore, therapeutic drug monitoring of plasma clozapine levels confers a significant benefit in everyday clinical practice by increasing the confidence of the prescribing doctor to the drug and the adherence of the patient to the treatment, mainly by ensuring effective treatment and limited dose-related side effects. In the present systematic review, we aimed at identifying how a full range of adverse effects relates to plasma clozapine levels, using the Jadad grading system for assessing the quality of the available clinical evidence. Our findings indicate that EEG slowing, obsessive-compulsive symptoms, heart rate variability, hyperinsulinemia, metabolic syndrome, and constipation correlate to plasma clozapine levels, whereas QTc, myocarditis, sudden death, leucopenia, neutropenia, sialorrhea, are rather unrelated. Rapid dose escalation at the initiation of treatment might contribute to the emergence of myocarditis, or leucopenia. Strategies for managing adverse effects are different in these conditions and are discussed accordingly.

[Therapeutic drug monitoring to optimize psychopharmacotherapy in children and adolescents - Update and guidelines for practice]

Therapeutic drug monitoring to optimize psychopharmacotherapy in children and adolescents - Update and guidelines for practice Abstract. Despite the improved evidence base, many uncertainties remain in child and adolescent psychiatric pharmacotherapy about the efficacy and tolerability of drugs, which are often prescribed off-label or in combination therapy in this age group. Because medium- to long-term use is unavoidable in many cases, clinicians should minimize adverse drug reactions as far as possible and tailor an effective dosage to the individual characteristics of the patient. Not only are children and adolescents particularly vulnerable to certain adverse drug effects, they are also exposed to iatrogenic risks from dosing or application errors, which can lead to under- or overdosing with correspondingly negative effects on the success of the therapy. In addition to determining a strict indication, it is therefore essential to establish precise dosage and systematic monitoring of the safety of the psychopharmacotherapy. This article introduces therapeutic drug monitoring as a useful clinical tool and describes how its correct application in practice can improve the efficacy as well as the safety and tolerability of psychotropic therapy in children and adolescents for the immediate benefit of patients. Keywords: Psychopharmacotherapy, adverse drug reactions, pharmacovigilance, therapeutic drug monitoring, quality assurance.

Investigating Predictors of Clozapine Response in Adolescents with Schizophrenia and Schizoaffective Disorder

Objectives: We aimed to determine the clinical predictors of clozapine response in patients with early-onset schizophrenia (EOS)/schizoaffective disorder and the effect of substance use disorder (SUD) on treatment outcomes. Methods: Medical records of patients with treatment-resistant EOS receiving clozapine were identified for data analysis dated between January 2015 and April 2020. Patients on clozapine were followed in an inpatient unit of a tertiary care mental health hospital. Using the Positive and Negative Symptom Scale (PANSS), ≥30% reduction was defined as the response criteria after clozapine treatment. Results: Of 50 subjects (age: 16.3 ± 1.3 years, 36.0% female), 22 subjects (44.0%) met the defined response criteria. Clozapine responder (CLZ-R) and clozapine nonresponder (CLZ-NR) groups were similar regarding age at illness onset, sex, and duration of untreated psychosis. The CLZ-R group had higher baseline positive PANSS scores (24.8 ± 8.1 vs. 17.1 ± 6.6, p = 0.001, d = 1.0) and total PANSS scores (94.8 ± 17.2 vs. 80.1 ± 19.8, p = 0.008, d = 0.8) compared with the CLZ-NR counterparts. The duration of hospital stay was longer in the CLZ-NR group (122.3 ± 48.2 vs. 87.3 ± 36.2 days, p = 0.007). Among 32 male patients, the presence of SUD (n = 9, 28.1%) was associated with a less reduction in total PANSS scores (F = 7.5, p = 0.010) and higher levels of positive symptoms at the end of the treatment (12.8 ± 4.1 vs. 18.8 ± 7.4, p = 0.006, d = 1.0). Synthetic cannabinoids were the most common substance type used among males with treatment-refractory EOS (25.0%). Conclusions: Our results did not support the role of sociodemographic variables in clozapine response. Positive symptoms and SUD yielded a prognostic value in patients receiving clozapine.

Retrospective Review of Clozapine Use in Children and Adolescents

OBJECTIVE

Literature describing use of clozapine by children and adolescents is limited. The primary study objective was to assess the patterns of clozapine use in an inpatient child and adolescent population.

METHODS

A retrospective review of child and adolescent inpatients receiving clozapine at a Canadian children's hospital from January 2000 through December 2014 was conducted. Interdisciplinary comprehensive data collection was conducted by experienced clinicians. Baseline population characteristics and psychiatric illness risk factors were captured. Illness symptoms and severity were assessed retrospectively using validated measures including the Brief Psychiatric Rating Scale (BPRS), Children's Global Assessment Scale (CGAS) and Clinical Global Impressions (CGI) scales. Estimated clozapine dosing requirements for each patient to achieve a serum level associated with response was calculated. Clozapine-related adverse events were captured.

RESULTS

Twenty-eight inpatients (64% female) receiving clozapine during the study period were identified. Mean age at clozapine initiation was 15.8 years. Twenty-three patients (82%) were taking clozapine at discharge, and of these, 22 patients (96%) experienced at least minimal improvement in BPRS and CGAS scores. Patients took a mean of 33.1 days from clozapine start to reach their maximum clozapine dosage, a mean maximum of 57% of their estimated clozapine dose requirement. Mean length of stay following clozapine initiation was 60.7 days. We observed a high rate of benign hematological adverse events, but no episodes of severe neutropenia. The majority of patients were of ethnicity associated with high risk for metabolic adverse events.

CONCLUSION

Most hospitalized, treatment-refractory children requiring clozapine clinically improve despite experiencing high, but largely manageable, adverse event rates.

Psychotropic drug concentrations and clinical outcomes in children and adolescents: a systematic review

INTRODUCTION

The use of psychotropic drugs in children and adolescents is widespread but associated with suboptimal treatment effects. Therapeutic drug monitoring (TDM) can improve safety of psychotropic drugs in children and adolescents but is not routinely performed. A major reason is that the relationship between drug concentrations and effects is not well known.

AREAS COVERED

This systematic review evaluated studies assessing the relationship between psychotropic drug concentrations and clinical outcomes in children and adolescents, including antipsychotics, psychostimulants, alpha-agonists, antidepressants, and mood-stabilizers. PRISMA guidelines were used and a quality assessment of the retrieved studies was performed. Sixty-seven eligible studies involving 24 psychotropic drugs were identified from 9,298 records. The findings were generally heterogeneous and the majority of all retrieved studies were not of sufficient quality. For 11 psychotropic drugs, a relationship between drug concentrations and side-effects and/or effectiveness was evidenced in reasonably reported and executed studies, but these findings were barely replicated.

EXPERT OPINION

In order to better support routine TDM in child- and adolescent psychiatry, future work must improve in aspects of study design, execution and reporting to demonstrate drug concentration-effect relationships. The quality criteria proposed in this work can guide future TDM research. Systematic review protocol and registration PROSPERO CRD42018084159.

Dose-Related Concentrations of Neuroactive/Psychoactive Drugs Expected in Blood of Children and Adolescents

PURPOSE

Therapeutic drug monitoring is highly recommended for children and adolescents treated with neurotropic/psychotropic drugs. For interpretation of therapeutic drug monitoring results, drug concentrations (C/D) expected in a "normal" population are helpful to identify pharmacokinetic abnormalities or nonadherence. Using dose-related concentration (DRC) factors obtained from pharmacokinetic data, C/D ranges expected under steady state can be easily calculated by multiplication of DRC by the daily dose. DRC factors, however, are defined only for adults so far. Therefore, it was the aim of this study to estimate DRC factors for children and adolescents and compare them with those of adults.

METHODS

To obtain pharmacokinetic data (apparent total clearance of drugs from plasma after oral administration, elimination half-life, area under the curve, and minimum serum drug concentration) from children and adolescents treated with psychotropic drugs, a systematic review of published literature was performed, and the pharmaceutical companies that market these drugs were contacted. Available information was used for the calculation of DRC factors.

RESULTS

Fourteen of 26 drugs had similar DRC factors to those reported for adults; 8 and 4 had higher and lower factors, respectively. The antidepressants citalopram, clomipramine, fluvoxamine, and imipramine and the antipsychotics haloperidol and olanzapine showed higher DRC factors than those calculated for adults. The DRC factors of amphetamine and methylphenidate were higher in children (6-12 years) but not in adolescents (13-17 years). On the contrary, the antipsychotic quetiapine and the mood-stabilizing antiepileptics lamotrigine, oxcarbazepine, and topiramate showed lower DRC factors than those calculated for adults.

CONCLUSIONS

It was concluded that concentrations of neuroactive/psychoactive drugs to be expected in blood for a given dose may differ between adults and children or adolescents, most probably owing to age-dependent differences in the elimination of these drugs.

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.

A Retrospective Multicenter Evaluation of Clozapine Use in Pediatric Patients Admitted for Acute Psychiatric Hospitalization

OBJECTIVES

Clozapine is the drug of choice for treatment-resistant schizophrenia. While pediatric clozapine use is not contraindicated, the literature describing its clinical application is limited. The primary objective of this study was to assess the use of clozapine in a child and adolescent population by characterizing the documented safety and clinical benefits of the medication.

METHODS

A multicenter retrospective study at sites in the United States and Australia included children and adolescents admitted to a psychiatric unit who were administered at least one dose of clozapine. Information related to demographics, patient history, past treatments, clozapine, and adverse events was collected.

RESULTS

Eighty-two patients from eight sites were included in this study. Patients were predominantly clozapine naive (76.8%), and most had a discharge diagnosis of a primary psychotic disorder (61%) or bipolar disorder (25.6%). Four clozapine discontinuations occurred during hospitalization due to severe neutropenia, ileus, need for diagnostic clarification, and significant psychomotor retardation. The remainder (n = 78) were discharged on a mean clozapine dose of 218.1 ± 142.2 mg. Sedation (26.8%) and sialorrhea (17.1%) were the most common documented adverse events. The mean number of previously trialed antipsychotics before clozapine was 3.5 ± 1.4 (range 1-10). Improvement with clozapine was documented as significant (31.7%), moderate (32.9%), minimal (12.2%), no improvement (2.4%), and not described (20.7%).

CONCLUSIONS

In this cohort, 95% of pediatric patients admitted with or started on clozapine during an acute psychiatric hospitalization were discharged on the medication. The high incidence of adverse events should reinforce to clinicians the need for vigilant monitoring. Pediatric guidelines recommend clozapine for refractory schizophrenia but stress the critical need to ensure an accurate diagnosis. Limited data exist for the use of clozapine in pediatric patients with other diagnoses.

Clozapine prescribing in adolescent psychiatry: survey of prescribing practice in in-patient units

Aims and Method

Clozapine is an effective drug in treatment-resistant schizophrenia, but it seems to be prescribed for few patients under the age of 18 years. This study reports a survey of consultant psychiatrists working in adolescent units in the UK, looking at their use of clozapine and experience with it.

Results

Out of 83 clinicians, 59 responded (71%). More than 40% of respondents do not use clozapine, and those who do may not always be following best practice recommendations. Reasons for not using clozapine, beliefs about its effectiveness and problems encountered in its use are described.

Clinical Implications

Clozapine may not always be made available to young people with treatment-resistant schizophrenia. There is a need for more education, guidance and debate on clozapine use in child and adolescent psychiatry.

CYP2C19*17 protects against metabolic complications of clozapine treatment

OBJECTIVES

Clozapine (CZ) is the most effective drug for managing treatment-resistant schizophrenic disorders. Its use has been limited due to adverse effects, which include weight gain and new-onset diabetes, but the incidence of these varies between patients.

METHODS

We investigated 187 Clozapine Clinic patients (of whom 137 consented for genotyping) for the presence of CYP2C19*17 and its association with CZ and norclozapine (NCZ) levels, and clinical outcomes.

RESULTS

Thirty-nine percent of genotyped patients were carriers of the CYP2C 19*17 polymorphism. This group demonstrated significantly higher NCZ serum levels, and significantly lower fasting glucose (5.66 ± 1.19 vs 6.72 ± 3.01 mmol/l, P = 0.009) and Hb1Ac (35.36 ± 4.78 vs 49.40 ± 20.60 mmol/mol, P = 0.006) levels compared to non-carriers of this polymorphism. CZ-treated patients with CYP2C19*17/*17 had a significantly lower prevalence of diabetes as well as a higher likelihood of clinical improvement of their schizophrenia, compared to those without this polymorphism (P = 0.012 and P = 0.031, respectively).

CONCLUSIONS

Our data suggest that CYP2C19*17 ultra-rapid-metaboliser status is a protective factor against the development of diabetes during clozapine treatment, and increases the likelihood of improvement in schizophrenia. The role of NCZ in treatment response and side effects, including metabolic syndrome, warrants further pharmacogenetic, pharmacokinetic and pharmacodynamic studies.

Strong Treatment Response and High Maintenance Rates of Clozapine in Childhood-Onset Schizophrenia

OBJECTIVE

Childhood-onset schizophrenia (COS) is a rare but severe form of the disorder, which is often treatment refractory. Short-term studies have indicated a greater differential efficacy, evident through effect sizes, favoring clozapine over other agents in alleviating negative symptoms in COS patients compared with adult-onset patients (AOS). There have been no data for COS patients on long-term compliance with clozapine treatment. Therefore, we wanted to know, over a span of up to 24 years, how many of our COS cohort had remained on clozapine for at least 2 years. We review short-term treatment data and present updated long-term data on compliance and functioning for our patients.

METHODS

We present the results for long-term medication maintenance over a 24 year observation period for our cohort of 131 patients. Of this cohort, 91.6% (120) were available for follow-up information from either in-person or telephone contact with the patient and/or family members. We defined clozapine compliance as ≥2 years receiving this medication and doing well.

RESULTS

We were able to contact 120 of the 131 patients. In spite of the additional cost and inconvenience of regular blood monitoring, 87 patients (72.5%, 87/120) adhered to long-term clozapine maintenance therapy with dosages ranging from 50 to 900 mg, and a median dosage of 500 mg. This rate exceeds the long-term clozapine maintenance rates reported for AOS patients.

CONCLUSIONS

Short-term data on differential efficacy and long-term maintenance data suggest a possibly greater efficacy of clozapine, relative to other antipsychotics, in COS than in AOS. Our overall findings indicate that very early-onset schizophrenic patients may be more responsive to clozapine. This extends other support for clozapine as an option in the treatment of early-onset schizophrenia.

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.

Pharmacokinetics and Tolerability of Lurasidone in Children and Adolescents With Psychiatric Disorders

PURPOSE

The aim of this study was to evaluate the pharmacokinetic (PK) profile and tolerability of lurasidone in children and adolescents with a range of psychiatric disorders.

METHODS

This multicenter, open-label, single and multiple ascending-dose study of the PK profile of lurasidone (20, 40, 80, 120, and 160 mg/d) enrolled outpatients aged 6 to 17 years with a diagnosis of attention deficit/hyperactivity disorder, bipolar spectrum disorder, or other psychiatric disorder. Serial blood samples were collected for analysis of PK parameters, including Cmax, Tmax, and AUC0-24.

FINDINGS

Exposure (Cmax and AUC0-24) to lurasidone and its active metabolites showed linear increases across the entire dose range. Slope estimates (95% CI) across the dose range studied was 0.90 ng · h/mL (0.74-1.06) for AUC0-24 and 0.70 ng/mL (0.52-0.87) for Cmax on day 10 or 12. Lurasidone exposure, after multiple-dose administration in this child and adolescent population, was similar to exposure observed at steady state in adults. The effects of dose on exposure to the 3 active metabolites of lurasidone were linear and similar after the administration of single and multiple doses. Adverse events were qualitatively similar to those reported in adults. Discontinuations due to adverse events were dose related, with doses <120 mg/d being better tolerated than higher doses, especially in younger children.

IMPLICATIONS

In this child and adolescent population, exposure parameters for lurasidone and its active metabolites were dose proportional in the range of 20 to 160 mg/d after the administration of single and multiple doses. These results suggest that lurasidone doses <120 mg/d were better tolerated compared with higher doses, especially in younger children. ClinicalTrials.gov identifier: NCT01620060.

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.

Hematological and cardiometabolic safety of clozapine in the treatment of very early onset schizophrenia: a retrospective chart review

OBJECTIVE

There are very few studies in the literature regarding clozapine use in children <13 years of age. In this retrospective chart review, we compared the safety of clozapine--as determined by hematological and cardiometabolic changes - to that of non-clozapine antipsychotics used in the treatment of childhood-onset schizophrenia (COS).

METHODS

The clozapine treatment group (CTG) consisted of 17 COS patients (mean age 10.4 ± 2 years) who were hospitalized in a psychiatric ward between the years 2005 and 2012. The control group consisted of 19 COS patients (mean age 10.1 ± 1.4 years) who were hospitalized in the same ward during the same time period, and were treated with non-clozapine antipsychotics. A retrospective chart review was conducted. Hematological (white blood cells, absolute neutrophil count [ANC], red blood cells, platelets), metabolic (aspartate transaminase, alanine transaminase, triglycerides, total cholesterol, bilirubin) and cardiac (heart rate) values were extracted from the medical charts.

RESULTS

The average follow-up periods for the CTG and the control group were 332.9 ± 200.5 days and 291.7 ± 157 days, respectively. In the CTG, moderate neutropenia (ANC<1500/mm(3)) and mild neutropenia (1500/mm(3)<ANC<2000/mm(3)) were observed in two children (12%) and one child (6%), respectively. The neutropenia was transient in all cases. Treatment with clozapine was permanently discontinued only in one child (6%). There were no cases of agranulocytosis or severe infection in the CTG. In the control group, two children (11%) showed hematological abnormalities. Hyperlipidemia was observed in one child (6%) in the CTG at release from the hospital. Significantly more children (47%) in the CTG had tachycardia (heart rate>100 beats per minute) at release from the hospital, compared with only one child (5%) in the control group (p=0.006).

CONCLUSIONS

It appears that clozapine use in very early onset schizophrenia is safe. Although hematological adverse effects did occur in our study, the rates were not much higher than those seen in the control group. We found that the hematological abnormalities in the CTG were mostly transient, and that treatment with clozapine can be safely continued or renewed.

Safety and pharmacokinetics of atypical antipsychotics in children and adolescents

Pediatric behavioral and affective disorders often require antipsychotic therapy, in combination with psychotherapeutic interventions, for their treatment and stabilization. Although pharmacotherapy can include either typical or atypical antipsychotics, the latter are generally preferred because of their apparently lower risk of adverse effects. Recent controlled trials have demonstrated the efficacy of some of these agents (including aripiprazole, clozapine, olanzapine, paliperidone, quetiapine, risperidone, ziprasidone) in adolescent schizophrenia and children or adolescent bipolar mania, or to treat severe aggression and self-injury in the context of autism in children and adolescents. Although few studies have systematically monitored their short- and, more importantly, long-term safety, current evidence indicates that sedation, hyperprolactinemia, and metabolic abnormalities such as excess weight gain, diabetes, and related cardiovascular effects were clinically relevant adverse effects in young patients, with the individual agents differing in their propensity to induce these effects. When prescribing antipsychotics for children and adolescents, physicians should therefore be aware of the specific adverse effect profiles and patients should be closely monitored for the short- and long-term development of adverse events. In pediatric patients, the starting dose, titration plan, and maintenance dose of antipsychotics must be based on their pharmacokinetics and metabolism, as in adults. Because there are significant individual differences in drug and active metabolite(s) pharmacokinetics and metabolism, which may be further affected by a number of confounding factors (including demographic variables, phenotype and drug interactions), therapeutic drug monitoring may be a valid tool for individualizing dosage, but its interpretation should also take account of changes in pharmacodynamic sensitivity with the development during childhood and adolescence.

Risk factors for neutropenia in clozapine-treated children and adolescents with childhood-onset schizophrenia

OBJECTIVE

The purpose of this study was to retrospectively analyze rates of neutropenia and risk factors for neutropenia in hospitalized children and adolescents treated with clozapine.

METHODS

A retrospective chart review was conducted for all patients who received clozapine at any time during a hospitalization at the National Institute of Mental Health (NIMH) between 1990 and 2011. All patients satisfied screening criteria for the NIMH childhood-onset schizophrenia study, including onset of psychosis before the age of 13 years. Absolute neutrophil count (ANC) values recorded during inpatient hospitalization were extracted for 87 eligible patients with a mean age of 13.35±2.46 years at hospitalization and a mean length of stay of 117±43 days.

RESULTS

Mild neutropenia only (lowest ANC<2000/mm3 but>1500/mm3) was observed in 27 (31%) patients and moderate neutropenia (any ANC<1500/mm3) was observed in 17 (20%) patients. There were no cases of agranulocytosis or severe infection. Significant risk factors for mild neutropenia compared with no hematologic adverse effects (HAEs) were male gender (p=0.012) and younger age (p<0.001). Male gender was also a significant risk factor for moderate neutropenia compared with no HAEs (p=0.003). If a child of African American ethnicity developed neutropenia during hospitalization at all that child was significantly more likely to develop moderate neutropenia than mild neutropenia only (p=0.017). African American boys had the highest rate of moderate neutropenia at 47%. Sixteen of the 17 patients exhibiting moderate neutropenia were successfully treated with clozapine by the time of discharge; 8 of these 16 required adjunctive lithium carbonate administration to maintain ANC>2000/mm3.

CONCLUSIONS

Our study shows that the rates of neutropenia in clozapine-treated children and adolescents are considerably higher than in the adult population. Younger age, African American ethnicity, and male gender were significant risk factors. These are also risk factors for benign neutropenia in healthy children and adolescents. Despite these high rates of neutropenia, all but one of the patients with neutropenia during hospitalization were successfully discharged on clozapine.

Age and sex impact clozapine plasma concentrations in inpatients and outpatients with schizophrenia

BACKGROUND

Although clozapine is primarily used in a younger to mid-life population of patients with psychosis, there are limited data on the clinical pharmacology of clozapine later in life. The objective of this study was to assess the magnitude and variability of plasma concentrations of clozapine and norclozapine across the lifespan in a real-world clinical setting.

DESIGN

A population pharmacokinetic study using nonlinear mixed effect modeling (NONMEM). Age, sex, height, weight, and dosage formulation were covariates.

SETTING

Inpatients and outpatients at the Centre for Addiction and Mental Health, Toronto, from 2001 to 2007.

PARTICIPANTS

Patients ranging in ages from 11 to 79 with schizophrenia spectrum disorders and prescribed clozapine (Clozaril).

MEASUREMENTS

A total of 1142 plasma clozapine and norclozapine concentrations (2,284 concentration measurements) from 391 patients with schizophrenia spectrum disorder.

RESULTS

A one-compartment model with first-order absorption and elimination best described the data. The population predicted clearance of clozapine for females was 27.1 L/h (SE 11.1%) and 36.7 L/h (SE 9.7%) for males. For norclozapine, clearance in females was 48.6 L/h (SE 10.8%) and 63.1 L/h (SE 9.3%) in males. The only covariates with a significant effect on clearance were age and sex: clearance for both parent and metabolite decreased exponentially with age at least 39 years.

CONCLUSIONS

Decreased clearance of clozapine and norclozapine with age results in increased blood concentrations and, hence, the potential for adverse drug reactions. These findings have particular clinical relevance for the dosing and safety monitoring of clozapine in older adults, highlighting a need for increased vigilance.

Regulation of PI3K/Akt signaling by N-desmethylclozapine through activation of δ-opioid receptor

We have previously reported that N-desmethylclozapine (NDMC), a major clozapine metabolite, acts as a δ-opioid receptor agonist. Here, we show that in different cellular systems NDMC regulates protein kinase B/Akt (Akt) signaling through the activation of δ-opioid receptors. In Chinese hamster ovary cells transfected with the human δ-opioid receptor (CHO/DOR), NDMC induced a time- and concentration-dependent phosphorylation of Akt at Thr308 and glycogen synthase kinase-3β (GSK-3β) at Ser9 and these effects were fully blocked by the δ-opioid receptor antagonist naltrindole. NDMC-induced Akt and GSK-3β phosphorylations were completely prevented by pertussis toxin, the Src tyrosine kinase inhibitor PP2 and the selective insulin-like growth factor-I (IGF-I) receptor tyrosine kinase inhibitor tyrphostin AG 1024. NDMC stimulated IGF-I receptor β subunit tyrosine phosphorylation and this effect was prevented by either naltrindole or PP2. Blockade of phosphatidylinositol 3-kinase (PI3K) α, but not PI3Kγ, suppressed NDMC-induced Akt and GSK-3β phosphorylation, whereas inhibition of Akt curtailed the stimulation of GSK-3β phosphorylation. In rat nucleus accumbens, NDMC induced Akt and GSK-3β phosphorylation either in vitro or in vivo and these effects were prevented by naltrindole. NDMC also regulated Akt and GSK-3β phosphorylation through δ-opioid receptors in NG108-15 cells. In these cells NDMC counteracted oxidative stress-induced apoptosis and the effect was lost following PI3K inhibition. These data demonstrate that in different cell systems NDMC can stimulate Akt signaling by activating Gi/Go-coupled δ-opioid receptors, which, at least in CHO/DOR cells, regulate PI3Kα through Src-dependent transactivation of the IGF-I receptor, and indicate that through this mechanism NDMC can exert neuroprotective effects.

Effects of repeated risperidone exposure on serotonin receptor subtypes in developing rats

Risperidone is an atypical antipsychotic drug that is widely prescribed to young patients with different psychotic disorders. The long-term effects of this antipsychotic agent on neuronal receptors in developing brain remain unclear and require further investigation. In this study, we examined the effects of long-term treatment of risperidone on two serotonin receptor subtypes in brain regions of juvenile rat. Levels of 5-HT(1A) and 5-HT(2A) receptors in forebrain regions of juvenile rats were quantified after 3 weeks of treatment with three different doses of risperidone (0.3, 1.0 and 3.0mg/kg). Findings were compared to previously reported changes in 5-HT receptors after risperidone treatment (3.0mg/kg) in adult rat brain. The three doses of risperidone selectively and dose-dependently increased levels of 5-HT(1A) receptors in medial-prefrontal and dorsolateral-frontal cortices of juvenile animals. The higher doses (1.0 and 3.0mg/kg) of risperidone also increased 5-HT(1A) receptor binding in hippocampal CA(1) region of juvenile but not adult rats. In contrast, the three doses of risperidone significantly reduced 5-HT(2A) labeling in medial-prefrontal and dorsolateral-frontal cortices in juvenile as well as in adult animals in an equipotent fashion. 5-HT(1A) and 5-HT(2A) receptors in other forebrain regions were not altered by repeated risperidone treatment. These findings indicate that there are differential effects of risperidone on 5-HT(1A) and 5-HT(2A) receptors in juvenile animals, and that the 5-HT system in developing animals is more sensitive than adults to the long-term effects of risperidone.

Donepezil use in children and adolescents with tics and attention-deficit/hyperactivity disorder: an 18-week, single-center, dose-escalating, prospective, open-label study

BACKGROUND

Striatal cholinergic dysfunction may be important in tics and attention-deficit/hyperactivity disorder (ADHD).

OBJECTIVE

The purpose of this study was to determine the safety profile of donepezil and whether it improves chronic tics in young patients with comorbid ADHD.

METHODS

This 18-week (14 weeks of open treatment followed by a 4-week washout period), single-center, dose-escalating, prospective, open-label trial was conducted in patients aged 7 to 17 years with tics, including chronic motor or vocal tics and Tourette's syndrome, and ADHD. Patients were treated with once-daily oral donepezil doses of 2.5 mg for 2 weeks, 5 mg for the next 6 weeks, and 10 mg for the last 6 weeks, followed by a 4-week washout period. Patients were evaluated using the Children's Global Assessment Scale; the Yale Global Tic Severity Scale (YGTSS); the Revised Conners' Parent Rating Scale; the Symbol and Digit Wisconsin Card Sorting Test; the Stroop black/white, color, and interference tests; the Rey Complex Figure Test; and the Children's Yale-Brown Obsessive Compulsive Scale at 4 visits: baseline, week 8 (5-mg dose), week 14 (10-mg dose), and week 18 (washout).

RESULTS

Seventeen males and 3 females (mean [SD] age, 11.3 [1.9] years [range, 8-14 years]; tic duration, 5.3 [1.9] years; ADHD duration, 6.5 [1.7] years) were included in this study. Tics were significantly reduced at the 10-mg (week-14) donepezil visit compared with the baseline and washout visits based on the total mean (SD) tic score of the YGTSS (18.6 [9.3] vs 12.2 [11.0]; P = 0.006). Fifty percent of patients withdrew and 65% experienced adverse events.

CONCLUSIONS

These preliminary results suggest that donepezil significantly reduced tics in these children and adolescents with comorbid ADHD who completed the study. No significant improvement in the symptoms of comorbid ADHD was found with the use of donepezil 10 mg. Donepezil 5 and 10 mg were not well tolerated in these children and adolescents.

Optimizing pediatric dosing: a developmental pharmacologic approach

Many physiologic differences between children and adults can result in age-related differences in pharmacokinetics. Understanding the effects of age on bioavailability, volume of distribution, protein binding, hepatic metabolic isoenzymes, and renal elimination can provide insight into optimizing doses for pediatric patients. We performed a search of English-language literature using the MEDLINE database regarding age and pharmacokinetics (1979-July 2008). We then evaluated the literature with an emphasis on drugs with one primary elimination pathway, such as renal clearance or a pathway involving a single metabolic isoenzyme. Our mechanistic-based analysis revealed that children need weight-corrected doses that are substantially higher than adult doses for drugs that are metabolically eliminated solely by the specific cytochrome P450 (CYP) isoenzymes CYP1A2, CYP2C9, and CYP3A4. In contrast, weight-corrected doses for drugs eliminated by renal excretion or metabolism involving CYP2C19, CYP2D6, N-acetyltransferase 2, or uridine diphosphate glucuronosyltransferases are similar in children and adults. In children, bioavailability of drugs with high first-pass metabolism is decreased for drugs metabolized by CYP1A2, CYP2C9, and CYP3A4. Limited data suggest that by age 5 years, bioavailability of drugs affected by efflux transporters should be equivalent to that of adults. Using a pharmacokinetics-based approach, rational predictions can be made for the effects of age on drugs that undergo similar pathways of elimination, even when specific pharmacokinetic data are limited or unavailable.

Determination of pharmacokinetic properties of clozapine and norclozapine in Korean schizophrenia patients

There is a wide interethnic variance in the pharmacokinetic profile of clozapine (CLZ), but the accumulated data are limited to some regional populations. In this study, we investigated the pharmacokinetic profile of CLZ in Korean patients and examined the association between serum CLZ parameters and clinical outcome. We assessed 78 Korean patients with schizophrenia who had been taking CLZ medication for more than 6 months. The patients were classified into three groups (good, moderate, and poor responders) according to their Clinical Global Impressions-Improvement scores. The serum concentrations of CLZ and norclozapine were 610.7+/-368.4 and 314.5+/-163.0 ng/ml (mean+/-SD), respectively, showing a large interindividual variation that was affected by dose, age, smoking habits, and sex by variable degrees. The pharmacokinetic profiles of Koreans were similar to those observed in Asians but quite different from those in Caucasians. Investigation on clinical responses revealed that the good or moderate responders clinically improved at a relatively low serum CLZ levels, whereas the poor responders showed less improvement despite the higher doses and serum levels. The metabolic ratio of the good responders was 0.65+/-0.20, higher than the poor responders (P=0.033). In this study, we identified a pharmacokinetic profile of CLZ in Korean schizophrenia patients and found a wide interindividual difference affected by various factors.

Agonist activity of N-desmethylclozapine at delta-opioid receptors of human frontal cortex

The clozapine metabolite N-desmethylclozapine (NDMC) has been recently shown to act at different neurotransmitter receptors and to display both antagonist and agonist activities. We have previously reported that in cells over-expressing the recombinant delta-opioid receptor NDMC behaved as partial agonist with high intrinsic activity, but its action at the receptors naturally expressed in human brain remained to be investigated. In the present study, we examined whether NDMC was able to bind to and activate delta-opioid receptors in membranes of post-mortem human frontal cortex. In radioligand binding assays, NDMC competition curves displayed high- (K(i)=26 nM) and low-affinity (K(i)=3 microM) components, whose proportion was regulated by guanine nucleotides in an agonist-like fashion. In functional assays, NDMC stimulated [(35)S]GTPgammaS binding (EC(50)=905 nM) and inhibited cyclic AMP formation (EC(50)=590 nM) as effectively as delta-opioid agonists, whereas clozapine was much less potent and efficacious and clozapine N-oxide was completely inactive. The NDMC agonist activity was potently antagonized by the delta-opioid antagonist naltrindole, but not by the micro-opioid receptor antagonist CTAP (D-phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH(2)) or the kappa-opioid antagonist nor-binaltorphimine. Moreover, blockade of either acetylcholine muscarinic, dopamine D(2) or serotonin 5HT(1A) receptors failed to affect NDMC agonist activity. These data demonstrate that at clinically relevant concentrations NDMC behaves as an efficacious agonist at delta-opioid receptors of human frontal cortex.

Role of muscarinic receptors in the activity of N-desmethylclozapine: reversal of hyperactivity in the phospholipase C knockout mouse

Activity of the cholinergic muscarinic system is associated with modulation of locomotor activity, although the precise mechanism remains unclear. The phospholipase C-beta1 knockout mouse displays both M1 muscarinic receptor dysfunction and a hyperactive locomotor phenotype. This mouse serves as an ideal model for the analysis of muscarinic modulation of locomotor activity. The clozapine metabolite N-desmethylclozapine (NDMC) has shown some promise as an alternative or adjunct treatment for psychotic disorders. NDMC shows strong muscarinic acetylcholine receptor affinities, which may contribute to the clinical efficacy of clozapine and account for the correlation between NDMC/clozapine ratio and treatment response. Administration of NMDC reversed a striking hyperactive phenotype in the phospholipase C-beta1 knockout mouse, whereas no significant effects were observed in wild-type animals. This highlights the potential role of muscarinic activity in the behavioural response to NDMC. The M1 muscarinic antagonist pirenzepine, however, also reduced the hyperactive phenotype of these mice, emphasizing the importance of muscarinic function in the control of locomotor behaviour, but also calling into question the specific mechanism of action of NMDC at muscarinic receptors.

Atypical antipsychotics in children with pervasive developmental disorders

The treatment of pervasive developmental disorders (PDDs) is a challenging task, which should include behavioral therapy modifications as well as pharmacologic therapy. There has been a lack of data on using medications in children with PDDs until recent years. Within the last 10 years, an increase in clinical research has attempted to provide efficacy and safety data to support the use of medications in children with PDDs. Double-blinded and open-label research of atypical antipsychotics has been of particular focus. Evidence shows that atypical antipsychotics (AAs) may be useful in treating certain symptoms associated with PDDs, such as aggression, irritability, and self-injurious behavior. This article reviews the literature regarding the use of AAs in children with PDDs. Of the AAs, risperidone has the largest amount of evidence with five published double-blinded, placebo-controlled trials and nine open-label trials. These risperidone trials have consistently shown improvements in aggression, irritability, self-injurious behavior, temper tantrums, and quickly changing moods associated with autistic disorder and other PDDs. Data for the other AAs are limited, but ziprasidone and aripiprazole appear to be promising treatment options. Based on clinical trials, olanzapine and quetiapine have shown minimal clinical benefit and a high incidence of weight gain and sedation. It should be noted that all AAs do have a risk of metabolic syndrome, and patients should be monitored appropriately while receiving these medications. Overall, AAs can be beneficial in alleviating behavioral symptoms, and should be considered an appropriate therapeutic option, as part of a comprehensive treatment strategy, for children with PDD.

Clozapine treatment of childhood-onset schizophrenia: evaluation of effectiveness, adverse effects, and long-term outcome

OBJECTIVE

Clozapine is a unique atypical antipsychotic with superior efficacy in treatment-resistant schizophrenia. Plasma concentration of clozapine and its major metabolite N-desmethylclozapine (NDMC) as well as the ratio of NDMC to clozapine have been reported to be predictors of clozapine response. Here we evaluate these as well as other measures in an effort to find predictors of response to clozapine in our early-onset treatment-refractory population.

METHOD

Fifty-four children and adolescents participated in double-blind (n = 22) or open-label (n = 32) clozapine trials. Clinical evaluations took place at baseline, week 6 on clozapine, and at 2- to 6-year follow-up. The data were analyzed in relation to demographics, age at onset, IQ, clozapine dose, and plasma concentrations of prolactin, clozapine, NDMC, and NDMC/clozapine ratio. Stepwise regression and correlation analyses were performed to find predictors of treatment response.

RESULTS

Clinical improvement after 6 weeks of clozapine treatment, as measured by the percentage of improvement on the Brief Psychiatric Rating Scale and the Scale for the Assessment of Positive Symptoms, was strongly associated with the NDMC/clozapine ratio at the 6-week time point (Pearson correlation coefficient: r = 0.41; p < .01 for Brief Psychiatric Rating Scale and r = 0.43; p < .01 for Scale for the Assessment of Positive Symptoms). Although the rate of side effects was higher than that typically found in the adult population, it did not appear to be related to clozapine dose, clozapine or NDMC plasma concentrations, or NDMC/clozapine ratio. Outcome at long-term follow-up, as measured by Children's Global Assessment Scale, was associated with lesser illness severity at baseline and with greater improvement during the initial 6 weeks of clozapine treatment.

CONCLUSIONS

The NDMC/clozapine ratio may be a valuable predictor of response to clozapine and may suggest new approaches to clozapine treatment.

Quantitative determination of clozapine in serum by instrumental planar chromatography

An instrumental planar chromatographic (HPTLC) method for quantitative analysis of clozapine in human serum was developed and validated. Clozapine was extracted with n-hexane-isoamyl alcohol (75:25 v/v). The chromatographic separation was achieved on precoated silica gel F 254 HPTLC plates using a mixture of chloroform and methanol (9:1 v/v) as mobile phase. Quantitative analyses were carried out by densitometry at a wavelength of 290 nm. The method was linear between 10 and 100 ng/spot, corresponding to 0.10 and 1.00 ng/microL of clozapine in human serum after extraction process and applying 10 microL to the chromatographic plates. The method correlation coefficient was 0.999. The intra-assay variation was between 2.10 and 3.33% (n = 5) and the interassay was between 2.67 and 4.44% (n = 9). The detection limit was 0.03 ng/microL, and the quantification limit was 0.05 ng/microL. The method proved to be accurate, with a recovery between 97.00 and 99.00%, with an RSD not higher than 7.22%, and was selective for the active principle tested. This method was successfully applied to quantify clozapine in patient serum samples. In conclusion, the method is useful for the quantitative determination of clozapine in serum.

Evaluation of N-desmethylclozapine as a potential antipsychotic--preclinical studies

There is growing interest in N-desmethylclozapine (NDMC), the major metabolite of clozapine, as a unique antipsychotic because it acts in vitro as a 5-HT(2) antagonist and as a partial agonist to dopamine D(2) and muscarinic receptors. To explore this, we compared NDMC to a typical (haloperidol), atypical (clozapine), and partial-agonist atypical (aripiprazole) antipsychotic in preclinical models. The comparison was carried out using: brain D(2) and 5-HT(2) receptor occupancy; animal models predictive of antipsychotic efficacy (amphetamine-induced hyperlocomotion (AIL) and conditioned avoidance response (CAR) models); measures predictive of side effects (catalepsy and prolactin elevation); and molecular markers predictive of antipsychotic action (striatal Fos induction). NDMC (10-60 mg/kg/s.c.) showed high 5-HT(2) (64-79%), but minimal D(2) occupancy (<15% at 60 mg/kg) 1 h after administration. In contrast to other antipsychotics, NDMC was not very effective in reducing AIL or CAR and showed minimal induction of Fos in the nucleus accumbens. However, like atypical antipsychotics, it showed no catalepsy, prolactin elevation, and minimal Fos in the dorsolateral striatum. It seems unlikely that NDMC would show efficacy as a stand-alone antipsychotic, however, its freedom from catalepsy and prolactin elevation, and its unique pharmacological profile (muscarinic agonism) may make it feasible to use this drug as an adjunctive treatment to existing antipsychotic regimens.

AC260584 (4-[3-(4-butylpiperidin-1-yl)-propyl]-7-fluoro-4H-benzo[1,4]oxazin-3-one), a selective muscarinic M1 receptor agonist, increases acetylcholine and dopamine release in rat medial prefrontal cortex and hippocampus

Both muscarinic and nicotinic receptors are implicated in cognition. We have previously suggested that stimulation of the muscarinic M1 receptor has a beneficial effect on cognition, based upon evidence that the muscarinic M1 receptor agonist of N-desmethylclozapine, the major metabolite of clozapine, may contribute to the ability of clozapine to improve some domains of cognition in schizophrenia. Present study examined the effectiveness of a new muscarinic M1 receptor agonist, 4-[3-(4-butylpiperidin-1-yl)-propyl]-7-fluoro-4H-benzo[1,4]oxazin-3-one (AC260584), to increase the release of acetylcholine and dopamine in the rat medial prefrontal cortex and hippocampus. Using microdialysis in awake, freely moving rats, AC260584, 3 and 10, but not 1 mg/kg (s.c.), significantly increased dopamine release in the medial prefrontal cortex and hippocampus. However, only the high dose of AC260584, 10 mg/kg (s.c.), significantly increased acetylcholine release in these regions. Moreover, the increases in acetylcholine release produced by AC260584, 10 mg/kg, were attenuated by the muscarinic M1 receptor antagonist telenzepine (3 mg/kg, s.c.) but not by the 5-HT1A receptor antagonist N-[2-(4-2-methoxyphenyl)-1-piperazinyl]-N-(2-pyridyl) cyclohexanecarboxamide (WAY100635, 0.2 mg/kg, s.c.). However, the increase in dopamine release produced by 10 mg/kg AC260584 was blocked by both telenzepine and WAY100635. In addition, pretreatment with the atypical antipsychotic drug risperidone (0.1 mg/kg, s.c.) potentiated AC260584 (1.0 mg/kg, s.c.)-induced acetylcholine and dopamine release in the medial prefrontal cortex. These findings suggest that the muscarinic M1 receptor agonist property of AC260584 contributes to its enhancement of cortical acetylcholine and dopamine efflux. Therefore, AC260584, as well as other muscarinic M1 receptor agonists, may be a valuable target for the development of drugs which can improve the cognitive deficits in schizophrenia and perhaps other neuropsychiatric disorders, as well.

N-Desmethylclozapine, a major clozapine metabolite, acts as a selective and efficacious delta-opioid agonist at recombinant and native receptors

The present study examined the effects of N-desmethylclozapine (NDMC), a biologically active metabolite of the atypical antipsychotic clozapine, at cloned human opioid receptors stably expressed in Chinese hamster ovary (CHO) cells and at native opioid receptors present in NG108-15 cells and rat brain. In CHO cells expressing the delta-opioid receptor (CHO/DOR), NDMC behaved as a full agonist both in stimulating [(35)S]GTPgammaS binding (pEC(50)=7.24) and in inhibiting cyclic AMP formation (pEC(50)=6.40). NDMC inhibited [(3)H]naltrindole binding to CHO/DOR membranes with competition curves that were modulated by guanine nucleotides in an agonist-like manner. Determination of intrinsic efficacies by taking into consideration both the maximal [(35)S]GTPgammaS binding stimulation and the extent of receptor occupancy at which half-maximal effect occurred indicated that NDMC had an efficacy value equal to 82% of that of the full delta-opioid receptor agonist DPDPE, whereas clozapine and the other clozapine metabolite clozapine N-oxide displayed much lower levels of agonist efficacy. NDMC exhibited poor agonist activity and lower affinity at the kappa-opioid receptor and was inactive at mu-opioid and NOP receptors. In NG108-15 cells, NDMC inhibited cyclic AMP formation and stimulated the phosphorylation of extracellular signal-regulated kinase 1/2 by activating the endogenously expressed delta-opioid receptor. Moreover, in membranes of different brain regions, NDMC stimulated [(35)S]GTPgammaS binding and regulated adenylyl cyclase activity and the effects were potently antagonized by naltrindole. These data demonstrate for the first time that NDMC acts as a selective and efficacious delta-opioid receptor agonist and suggest that this unique property may contribute, at least in part, to the clinical actions of the atypical antipsychotic clozapine.

Review of antipsychotics in children and adolescents

The use of antipsychotics in children and adolescents in the clinical setting is increasing. This article reviews 77 clinical trials published in the last 10 years, investigating their efficacy, effectiveness, safety and pharmacokinetic data in paediatric populations. The diagnostic categories in which the antipsychotics are commonly used (schizophrenia, pervasive developmental disorders, Tourette's disorder, mental retardation/subaverage intelligence, mood disorders and disruptive behaviour disorders) were used in order to review the evidence and effectiveness. All randomised, double-blind, placebo-controlled trials from the past decade are also summarised. This review refers to recent relevant practice parameters, guidelines and reviews throughout the text. Consistent with previous reviews, it is concluded that the recent trend of increased use of antipsychotics in children and adolescents is not adequately supported by evidence. Specific suggestions have been provided on how to incorporate the existing evidence base into clinical decision making. The review ends with the authors' opinion on the clinical and research implications for the field and future directions.

Clinical drug monitoring in child and adolescent psychiatry: side effects of atypical neuroleptics

OBJECTIVE

The aim of this study was to improve and evaluate the practibility of a method for the assessment of drug-associated side effects, and we implemented a clinical drug monitoring for atypical neuroleptics.

METHODS

Side effects of initially hospitalized patients treated with clozapine (n = 16), olanzapine (n = 16), and risperidone (n = 19) were prospectively monitored on a weekly basis for the first 3 weeks. In the case of stable medication, measurements of all variables were made every 4 weeks or upon discharge. We used the Dosage Record Treatment Emergent Symptom Scale (DOTES) in a supplemented version to measure the presence and severity of side effects.

RESULTS

Drowsiness and decreased motor activity were common, especially in the first 2 weeks. Orthostatic hypotension, increased salivation, constipation, and nasal congestion were seen in more than 30% to 60% of patients treated with clozapine and were less common in adolescents treated with olanzapine and risperidone. Rigidity, tremor, and dystonia were seen in 5% to 15% of patients treated with risperidone and olanzapine. The average weight gain after 6 weeks of treatment with the atypical neuroleptics was significantly higher for the olanzapine group (4.6 +/- 1.9 kg) than for the risperidone (2.8 +/- 1.3 kg) and clozapine (2.5 +/- 2.9 kg) groups.

CONCLUSIONS

The authors' supplemented DOTES version is generally applicable to clinical use in mental health centers. The differences among the side effects of these three agents may affect compliance with medication and medical risks of metabolic syndrome, diabetes, and cardiovascular disease. More research on the short- and long-term safety of psychotropic drugs in children and adolescents, using standardized methods, should be considered.

Antipsychotic poisoning in young children: a systematic review

The aim of this review was to determine the spectrum and severity of effects of unintentional antipsychotic poisoning in children. A computerised literature search of MEDLINE (1966 to February 2005) and EMBASE (1980 to February 2005) was undertaken. The Internet was searched using URL: www.google.com. The proceedings of the North American Congress of Clinical Toxicology (NACCT) and the European Association of Poisons Centres and Clinical Toxicologists (EAPCCT) were hand searched. All cases of unintentional antipsychotic (all classes) poisoning in children aged 0-6 years were included. The data extracted included the age, weight, antipsychotic, dose, clinical effects, treatment and outcomes. The toxic dose was estimated as the lowest dose causing objective adverse effects.Sixty-eight reports were identified. Few contained all of the required information. Most of the case series included multiple antipsychotics with limited information on individual drugs or all ages with limited paediatric information. For most antipsychotics the ingestion of one tablet caused symptoms that were sometimes severe and usually lasted from 1 to 3 days. Extrapyramidal symptoms (EPS) were often delayed for up to 12-24 hours. Chlorpromazine caused CNS depression, hypotension and miosis; EPS and cardiac effects were rare, and the toxic dose was estimated to be 15 mg/kg. Haloperidol caused drowsiness (rarely coma) and over one-half of patients had neuromuscular effects (mainly EPS), with a toxic dose estimated at 0.15 mg/kg. Thioridazine caused CNS depression and potentially cardiac effects, with a toxic dose of 1.4 mg/kg. Atypical antipsychotics caused significant CNS depression (except risperidone); EPS were less common. Toxic doses were clozapine 2.5 mg/kg, olanzapine 0.5 mg/kg and aripiprazole 3 mg/kg. EPS responded to anticholinergic drug treatment. In summary, unintentional antipsychotic ingestion in children can cause severe effects that last 1-3 days, often with one tablet. Children potentially ingesting a toxic dose or who are symptomatic should be considered for assessment in hospital. Most cases resolve with good supportive care. Toxic doses are only estimates that are based on limited data and should be used with caution until prospective studies are undertaken.

N-desmethylclozapine, a major metabolite of clozapine, increases cortical acetylcholine and dopamine release in vivo via stimulation of M1 muscarinic receptors

The active moiety of clozapine, the prototypical antipsychotic drug, consists of clozapine and its major metabolite, N-desmethylclozapine (NDMC). Previous studies have suggested that NDMC may be more important than the patent compound itself for the improvement in cognition in patients with schizophrenia treated with clozapine. While the pharmacology of clozapine and NDMC are similar in most respects, NDMC has been shown to be an M1 muscarinic receptor partial agonist whereas clozapine is an M1 antagonist in vitro and in vivo. We hypothesized that NDMC may improve cognition by increasing dopamine (DA) and acetylcholine (ACh) release in medial prefrontal cortex (mPFC) via direct stimulation of M1 receptors, whereas both NDMC and clozapine itself would do so by other mechanisms as well, and that clozapine would inhibit the M1 agonist effect of NDMC. In the present study, using microdialysis in awake, freely moving rats, we found that NDMC at doses of 10 and 20, but not 5 mg/kg, significantly increased DA and ACh release in the mPFC and HIP, but not in the nucleus accumbens (NAC). The M1-preferring antagonist, telenzepine (3 mg/kg), completely blocked NDMC (10 mg/kg)-induced increases in cortical DA and ACh release. Clozapine (1.25 mg/kg), which by itself had no effect on DA or ACh release in the cortex, blocked NDMC (10 mg/kg)-induced ACh, but not DA, release in the mPFC. The 5-HT1A receptor antagonist, WAY100635 (0.2 mg/kg) blocked NDMC (20 mg/kg)-induced cortical DA but not ACh release. These findings suggest that: (1) NDMC is an M1 agonist while clozapine is an M1 antagonist in vivo; (2) M1 agonism of NDMC can contribute to the release of cortical ACh and DA release; (3) NDMC, because of its M1 agonism, may more effectively treat the cognitive impairments observed in schizophrenia than clozapine itself; and (4) M1 receptor agonism may be a valuable target for the development of drugs that can improve cognitive deficit in schizophrenia, and perhaps other neuropsychiatric disorders as well.

Second-generation antipsychotic medications in children and adolescents

OBJECTIVE

We reviewed available pediatric literature on second-generation antipsychotic medications to assess current evidence of efficacy and safety.

METHOD

An English language MEDLINE search (1974-2003) was conducted using key words-atypical antipsychotics, children and adolescents, toxicity, clozapine, risperidone, olanzapine, quetiapine, ziprasidone, and aripiprazole. Additional efficacy and safety data were obtained from drug manufacturers.

RESULTS

We identified 176 reports, including 15 double-blind, controlled trials, 58 openlabel studies, 18 retrospective chart reviews, and 85 case series/reports. The majority of these studies (43%) were of risperidone. Evidence suggests that second-generation antipsychotics are efficacious in the treatment of psychosis, bipolar disorders, pervasive developmental disorders, and Tourette's Disorder, and are potentially useful in mental retardation, conduct disorder, and severe attention deficit hyperactivity disorder (ADHD). The most frequently reported side effects included cardiovascular effects, weight gain, sedation, sialorrhea, extrapyramidal signs, and hyperprolactinemia, although the relative frequencies of these untoward effects vary among medications.

CONCLUSION

Although the evidence base for pediatric use of second-generation antipsychotics is expanding, the majority of available studies are anecdotal, or short-term, openlabel trials. Reports suggest that these compounds are effective for a variety of psychiatric disorders in children and adolescents, but additional double-blind, controlled studies are required to establish definitive efficacy. Although these medications appear to be well tolerated in short-term studies, long-term follow-up investigations and ongoing clinical monitoring are necessary to confirm their safety in this age group.

The role of M1 muscarinic receptor agonism of N-desmethylclozapine in the unique clinical effects of clozapine

RATIONALE

Clozapine is a unique antipsychotic, with efficacy against positive symptoms in treatment-resistant schizophrenic patients, and the ability to improve cognition and treat the negative symptoms characteristic of this disease. Despite its unique clinical actions, no specific molecular mechanism responsible for these actions has yet been described.

OBJECTIVES AND METHODS

To comprehensively profile a large library of neuropsychiatric drugs, including most antipsychotics, at human monoamine receptors using R-SAT, an in vitro functional assay.

RESULTS

Profiling revealed that N-desmethylclozapine (NDMC), the principal metabolite of clozapine, but not clozapine itself, is a potent and efficacious muscarinic receptor agonist, a molecular property not shared by any other antipsychotic. To further explore the role of NDMC muscarinic receptor agonist properties in mediating the physiological actions of clozapine, systemically administered NDMC was found to stimulate the phosphorylation of mitogen-activated protein kinase (MAP kinase) in mouse CA1 hippocampal neurons, an effect that was blocked by scopolamine, confirming central M1 muscarinic receptor agonist activity in vivo. Lastly, an analysis of clozapine and NDMC serum levels in schizophrenic patients indicated that high NDMC/clozapine ratios better predicted improvement in cognitive functioning and quality of life than the levels of either compound alone.

CONCLUSIONS

The muscarinic receptor agonist activities of NDMC are unique among antipsychotics, and provide a possible molecular basis for the superior clinical effects of clozapine pharmacotherapy.

Clinical effectiveness of new generation antipsychotics in adolescent patients

In addition to management of symptoms of disease, pharmacological interventions in adolescents with psychotic disorders must be clinically effective to provide the best possible outcome in terms of well-being, functioning, and disease burden. Six outcome domains should be considered: symptoms of disease, tolerability, everyday functioning, subjective well-being, family/career burden, and treatment adherence. To date, few studies have compared the clinical effectiveness of the different new generation antipsychotics in adolescents. However, clear differences exist between available agents, particularly in terms of tolerability profile. This review will focus on the particular issues that clinicians need to consider in order to maximise the clinical effectiveness of the new generation antipsychotics in adolescent patients with psychosis. For example, adolescents are not only more susceptible to the side effects of antipsychotic medication than adults, but they are also more likely to be sensitive to the negative impact of side effects on appearance, body image, and self-esteem. Data available in children and adolescents will be reviewed, and the practical implications for patient management will be highlighted. The importance of dosing the new generation antipsychotics appropriately will also be discussed.