Serum concentrations of clozapine and norclozapine in the prediction of relapse of patients with schizophrenia

Optimisation of pharmacotherapy in psychiatry through therapeutic drug monitoring, molecular brain imaging and pharmacogenetic tests: focus on antipsychotics

BACKGROUND

For psychotic disorders (i.e. schizophrenia), pharmacotherapy plays a key role in controlling acute and long-term symptoms. To find the optimal individual dose and dosage strategy, specialized tools are used. Three tools have been proven useful to personalize drug treatments: therapeutic drug monitoring (TDM) of drug levels, pharmacogenetic testing (PG), and molecular neuroimaging.

METHODS

In these Guidelines, we provide an in-depth review of pharmacokinetics, pharmacodynamics, and pharmacogenetics for 50 antipsychotics. Over 30 international experts in psychiatry selected studies that have measured drug concentrations in the blood (TDM), gene polymorphisms of enzymes involved in drug metabolism, or receptor/transporter occupancies in the brain (positron emission tomography (PET)).

RESULTS

Study results strongly support the use of TDM and the cytochrome P450 (CYP) genotyping and/or phenotyping to guide drug therapies. Evidence-based target ranges are available for titrating drug doses that are often supported by PET findings.

CONCLUSION

All three tools discussed in these Guidelines are essential for drug treatment. TDM goes well beyond typical indications such as unclear compliance and polypharmacy. Despite its enormous potential to optimize treatment effects, minimize side effects and ultimately reduce the global burden of diseases, personalized drug treatment has not yet become the standard of care in psychiatry.

Effect of smoking habits and concomitant valproic acid use on relapse in patients with treatment-resistant schizophrenia receiving clozapine: A 1-year retrospective cohort study

INTRODUCTION

No study has investigated the impact of smoking habits and concomitant valproic acid (VPA) use on clinical outcomes in maintenance treatment with clozapine. Thus, we aimed to examine the effect of smoking habits and concomitant VPA use on relapse during the first year after discharge in patients with treatment-resistant schizophrenia (TRS) receiving clozapine.

METHODS

This retrospective cohort study included patients with TRS who were initiated on clozapine during hospitalization and discharged between April 2012 and January 2021 in two tertiary psychiatric hospitals in Japan. Relapse was defined as rehospitalization due to psychiatric exacerbation during the first year after discharge. A multivariable Cox proportional hazards regression analysis was performed to analyze the effect of smoking habits and concomitant VPA use on relapse. Subgroup analyses were also conducted to examine potential interactions between smoking habits and concomitant VPA use.

RESULTS

Among the included 192 patients, 69 (35.9%) met the criteria of relapse. While smoking habits (adjusted hazard ratio [aHR], 2.27; 95% confidence interval [CI], 1.28-4.01; p < 0.01) independently increased the risk of relapse, a significant interaction for relapse risk was found between smoking habits and concomitant VPA use (p-interaction = 0.015). Concomitant VPA use may be an effective modifier of the increased relapse risk associated with smoking habits. Among patients who smoked, those using VPA concomitantly exhibited a higher risk of relapse (aHR, 5.32; 95% CI, 1.68-16.9; p < 0.01) than those not using VPA (aHR, 1.41; 95% CI, 0.73-2.70; p = 0.30).

CONCLUSION

The findings suggest that the combination of smoking habits and concomitant VPA use may increase the risk of relapse after discharge. Future studies are required to elucidate the mechanisms underlying these findings, such as a decrease in clozapine blood levels.

[Therapeutic drug monitoring of clozapine]

Clozapine is a prototypical atypical antipsychotic used to treat severe schizophrenia and for which a therapeutic drug monitoring (TDM) is quite commonly proposed. Clozapine is rapidly absorbed (maximum concentration reached within 1 to 4hours), and is extensively metabolized in the liver by CYP1A2 to an active metabolite (and to a lesser extent, to inactive metabolites via other enzymes). Its half-life is 8 to 16h. A therapeutic range has been proposed for clozapine as some studies have reported both a relationship between low plasmatic concentrations and resistance to treatment (threshold level is likely between 250 and 400μg/L), and a relationship between high plasmatic concentrations and an increase in the occurrence of toxicity (alert level=1000μg/L). Given the data obtained in different studies, the TDM was evaluated for this molecule, to recommended.

Feasibility and Effect of Increasing Clozapine Plasma Levels in Long-Stay Patients With Treatment-Resistant Schizophrenia

BACKGROUND

It is unknown whether increasing the clozapine plasma level to 400, 750, or even 1000 ng/mL is a feasible and effective strategy in patients with treatment-resistant schizophrenia (TRS). We investigated this in long-stay patients with TRS.

METHODS

In long-stay TRS patients, doses of clozapine were increased gradually to reach target plasma levels of 400, 750, or 1000 ng/mL, depending on the clinical response and tolerability. After an effective or tolerated level was reached, positive and negative syndrome scale scores were evaluated after 3 months and 1 year.

RESULTS

Twenty-eight patients were included. Overall, 54% of the patients, and especially patients 60 years and older, could not achieve one of the clozapine target levels because of adverse effects. Three physically vulnerable patients died, probably not directly related to clozapine use. Although only 21% of patients achieved a more than 20% reduction in total symptoms at the 1-year follow-up, the mean severity of positive symptoms decreased from 18.18 to 15.10 ( P < 0.01). The largest decrease in positive symptoms was seen in TRS patients who achieved a plasma level of 750 ng/mL of clozapine.

CONCLUSIONS

Most TRS patients older than 60 years could not tolerate high clozapine levels and so this should not be attempted in older or otherwise physically vulnerable patients. Increasing clozapine levels to approximately 750 ng/mL in middle-aged patients with longstanding TRS may modestly reduce the severity of positive symptoms and improve the response rate.

The effect on relapse rate and psychiatric symptomatology: Switching a combination of first- and second-generation antipsychotic polypharmacy to antipsychotic monotherapy in long-term inpatients with schizophrenia and related disorders. A pragmatic randomized open-label trial (SwAP trial)

BACKGROUND

There is little evidence to support the use of antipsychotic polypharmacy, and there are concerns about safety and side effects. Nonetheless, it is commonly used in the treatment of long-term inpatients with schizophrenia. This study investigated the effects of switching from a combination of first- and second-generation antipsychotics (FGA and SGA) to monotherapy (FGA or SGA) on relapse rates and psychiatric symptomatology.

METHODS

Institutionalized patients with chronic psychotic disorders using a combination of SGA and FGA (n = 136) participated in a randomized open-label trial. The SWITCH group discontinued either FGA or SGA, the STAY group continued combination treatment. Relapse and psychotic symptoms were measured at baseline and during follow-up at 3, 6, and 9 months. Psychiatric symptomatology was measured using the Brief Psychiatric Rating Scale (BPRS). Relapse was defined as (i) an increase in BPRS score of at least 2 points on any item, or (ii) an increase of at least 4 points in total BPRS score and an adjustment of antipsychotics.

RESULTS

A logistic regression model, corrected for sex, showed that the probability of relapse was significantly lower in the SWITCH group: 0.29 (95% CI 0.13-0.62). The protective effect of switching to monotherapy was attributable to patients continuing clozapine as monotherapy. For patients who did not experience a relapse nor dropped out, BPRS total scores decreased significantly more in the SWITCH group (p = 0.0001).

CONCLUSION

Switching from a combination of FGA and SGA to monotherapy in long-term inpatients does not increase the relapse rate and may even reduce it.

Determination of clozapine and norclozapine in dried plasma spot and dried blood spot by liquid chromatography-tandem mass spectrometry

The use of alternative blood sampling strategies in clozapine (CLZ) therapeutic drug monitoring (TDM) aims to facilitate collection and improve drug therapy and adherence. This study aimed to develop and validate two methods for the determination CLZ and norclozapine (NOR) in dried blood spots (DBS) and dried plasma spots (DPS) by high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). The analytes were extracted from one 10 microliter volumetric DBS disc punch and from one 6 mm DPS disc punch with methyl tert-butyl ether: methanol (1:9, v/v) and injected into the HPLC-MS/MS with Atmospheric pressure chemical ionization (APCI) source. Separation was performed in a phenyl column, with mobile phase ammonium formate 1 mM pH 4.0 with methanol in gradient mode. The method was linear from 50 to 1500 ng/ml (r > 0.99), with accuracy between 98% and 105% in DBS and 91-101% in DPS, and intra- and inter-assay CV% from 5.23% to 9.35% in DBS and 2.22-11.36% in DPS for both analytes. The matrix effect was compensated by the internal standard, between - 5.1-6.89% in DBS and - 2.45-5.74% in DPS. The average extraction efficiency was 63-67% for CLZ and 58-69% for NOR with no significant impact of hematocrit (HCT). The analytes were stable in the dried matrices stored up to 42 °C for 26 days. The method was applied in the evaluation of clozapine therapy in 13 schizophrenic patients with mean serum levels of 401 ng/ml (43-914 ng/ml). Only 38% were within the therapeutic range, 46% below and 23% above. CLZ and NOR concentrations in dried samples were highly correlated to serum levels, with greater accuracy for DPS compared to DBS (97 versus 89%, and 99 versus 131%, for CLZ and NOR, respectively). Our data support the use of DBS and DPS as alternative sampling strategies in CLZ therapeutic drug monitoring, with satisfactory performance and logistics advantages.

Underuse of recommended treatments among people living with treatment-resistant psychosis

BACKGROUND

International guidelines recommend that individuals with treatment-resistant psychosis must be treated with clozapine. ECT has also been reported to improve symptom profiles. Identification of clozapine and/or ECT use in real-world practice enables understanding of the extent to which this evidence-base is implemented.

SETTING

Statewide public health tertiary referral service, the Tertiary Referral Service for Psychosis (TRSP), NSW, Australia.

OBJECTIVES

To (i) describe clinical characteristics of individuals with treatment-resistant psychosis and to detail the proportion who had received a trial of clozapine or ECT at any point during their illness course; (ii) describe the characteristics of the treatment trials in both those currently on clozapine and those previously on clozapine; (iii) document reasons in relevant individuals why clozapine had never been used.

METHODS

All TRSP clients who met the criteria for treatment resistance (TR) were included. A detailed casenote review was conducted to examine whether clozapine and/or ECT had ever been prescribed. Characteristics of clozapine and ECT trials were documented. Tertiary service treatment recommendations are described.

FINDINGS

Thirty-six of 48 individuals had TR. They had marked clinical and functional impairment. A minority were currently receiving clozapine (n = 14/36). Most had received a clozapine trial at some point (n = 32/36). Most experienced persistent clinical symptoms while on clozapine (n = 29/32). Clozapine plasma levels were very rarely reported (4/32). Augmentation and antipsychotic polypharmacy were common among those currently on clozapine. The median clozapine trial duration was 4.0 (IQR: 3.0-20.3) months in individuals previously prescribed clozapine. Reasons for clozapine discontinuation included intolerable side effects (n = 10/18) and poor adherence (n = 7/18). One-quarter of TR individuals had trialed ECT (n = 9/36). Tertiary service recommendations included routine plasma monitoring to optimize dose among people currently on clozapine; clozapine retrial in those previously treated; and clozapine initiation for those who had never received clozapine. ECT was recommended to augment clozapine and as an alternative where clozapine trial/retrial was not feasible.

CONCLUSION

Among people with TR referred to a tertiary service, clozapine and ECT were underutilized. Clozapine trials are typically terminated without an adequate trial. Strategies to optimize the use of clozapine therapy and ECT in clinical settings are needed to increase the therapeutic effectiveness of evidence-based therapies for treatment-resistant psychosis.

Pharmacometabolomics-guided clozapine therapy in treatment resistant schizophrenia: Preliminary exploration of future too near

AIM

To study the association of clozapine pharmacometabolomics and clozapine response in Asian patients with treatment-resistant schizophrenia (TRS).

METHOD

A cross-sectional study was performed on 50 consecutive TRS patients following up in psychiatry department of the tertiary care hospital. Demographic details, response assessment, were collected on the case record form. A blood sample was also collected for trough concentration assessment of drug and its metabolites. Clozapine (CLZ) the parent drug and its two major metabolites - Clozapine N oxide (CNO) and N-Desmethyl clozapine (N-DSMC) levels were assessed using a high-performance liquid chromatography method. Clozapine responders and nonresponders patients were classified based upon Andreasen criteria.

RESULTS

The average trough concentration of CNO, N-DSMC, and CLZ were 123 ± 76.04, 171.93 ± 93.24, 229.27 ± 124.25 ng/ml, respectively. The two patient subgroups did not differ for CLZ, CNO, and N-DSMC concentrations statistically. However, clozapine nonresponse was associated with a higher CLZ/N-DSMC ratio (p = 0.03) and clozapine dose (p = 0.01). The receiver operator characteristic curve showed that the cut-off CLZ/N-DSMC ratio of 1.54 with a sensitivity of 85% and a positive predictive value of 84% for identifying nonresponders.

CONCLUSION

CLZ/N-DSMC ratio and clozapine dose were identified as significant variables for future dose optimization algorithms. Pharmacometabolomics-guided clozapine therapy has the potential to revolutionize TRS management.

Clozapine levels as a predictor for therapeutic response: A systematic review and meta-analysis

OBJECTIVES

Clozapine levels may be a more useful predictor of therapeutic response than the dose, given the variability in clozapine metabolism between individuals. We therefore systematically reviewed and meta-analysed the impact of clozapine levels on response and/or relapse to provide guidance on optimal clozapine levels.

METHODS

We systematically searched PubMed, PsycInfo and Embase for studies exploring clozapine levels and response and/or relapse. Our primary meta-analysis was rates of response above and below clozapine level thresholds of 350 ng/ml and 600 ng/ml. Secondary analyses were undertaken of mean clozapine levels, dose and concentration/dose (C/D) ratio and response and/or relapse. A meta-regression by study duration was conducted.

RESULTS

Twenty studies met inclusion criteria. Clozapine levels above 350 ng/ml were associated with statistically significantly higher rates of response (OR 2.27 95% CI 1.40-3.67, p < 0.001), but not above 600 ng/ml (OR 1.40 95% CI 0.85-2.31, p = 0.19). Higher mean clozapine levels were associated with better rates of response (SMD 0.24, 95% CI 0.00-0.49, p = 0.05), and lower rates of relapse (SMD -0.72, 95% CI -1.26 to -0.19, p = 0.008). By contrast, neither clozapine dose nor C/D ratio was associated with differing rates of response. Similarly, study duration did not affect outcome.

CONCLUSIONS

Our findings are in keeping with current guidelines that recommend targeting clozapine levels above 350 ng/ml before augmentation is considered. As some clozapine associated ADRs are dose dependent, levels above 600 ng/ml may have an unfavourable risk-benefit ratio.

Physiologically-based pharmacokinetic model for clozapine in Korean patients with schizophrenia

Clozapine has been used as a treatment of schizophrenia. Despite its large interindividual variability, few reports addressed the physiologically-based pharmacokinetic modeling and simulation (PBPK M&S) of clozapine in patients. This study aimed to develop a PBPK M&S of clozapine in Korean patients with schizophrenia. PBPK modeling for clozapine was constructed using a population-based PBPK platform, the SimCYP^® Simulator (V19; Certara, Sheffield, UK). The PBPK model was developed by optimizing the physiological parameters of the built-in population and compound libraries in the SimCYP^® Simulator. The model verification was performed with the predicted/observed ratio for pharmacokinetic parameters and visual predictive checks (VPCs) plot. Simulations were performed to predict toxicities according to dosing regimens. From published data, 230 virtual trials were simulated for each dosing regimen. The predicted/observed ratio for the area under the curve and peak plasma concentration was calculated to be from 0.78 to 1.34. The observation profiles were within the 5th and 95th percentile range with no serious model misspecification through the VPC plot. A significant impact on age and gender was found for clozapine clearance. The simulation results suggested that 150 mg twice a day and 150 mg three times a day of clozapine have toxicity concerns. In conclusion, a PBPK model was developed and reasonable parameters were made from the data of Korean patients with schizophrenia. The provided model might be used to predict the pharmacokinetics of clozapine and assist dose adjustment in clinical settings.

Outcomes in treatment-resistant schizophrenia: symptoms, function and clozapine plasma concentrations

BACKGROUND

Clozapine is the only medication licenced for treating patients with treatment-refractory schizophrenia. However, there are no evidence-based guidelines as to the optimal plasma level of clozapine to aim for, and their association with clinical and functional outcome.

OBJECTIVE

We assessed the relationship between clinical and functional outcome measures and blood concentrations of clozapine among patients with treatment-refractory psychosis.

METHODS

Data were reviewed in 82 patients with treatment-refractory psychosis admitted to a specialised tertiary-level service and treated with clozapine. Analysis focussed on the relationship between clozapine and norclozapine plasma concentrations and the patient's clinical symptoms and functional status.

RESULTS

Clinical symptom improvement was positively correlated with norclozapine plasma concentrations and inversely correlated with clozapine to norclozapine plasma concentrations ratio. Clozapine concentrations showed a bimodal association with clinical improvement (peaks around 350 and 660 ng/ml). Clinical symptom improvement correlated with functional outcomes, although there was no significant correlation between the latter and clozapine or norclozapine plasma concentrations.

CONCLUSION

Clozapine treatment was associated with optimal clinical improvement at two different peak plasma concentrations around 350 and 650 ng/ml. Clinical improvement was associated with functional outcome; however, functionality was not directly associated with clozapine concentrations. A subset of patients may require higher clozapine plasma concentrations to achieve clinical improvement.

ASHP Therapeutic Position Statement on the Use of Antipsychotic Medications in the Treatment of Adults with Schizophrenia and Schizoaffective Disorder

In an effort to expedite the publication of articles related to the COVID-19 pandemic, AJHP is posting these manuscripts online as soon as possible after acceptance. Accepted manuscripts have been peer-reviewed and copyedited, but are posted online before technical formatting and author proofing. These manuscripts are not the final version of record and will be replaced with the final article (formatted per AJHP style and proofed by the authors) at a later time.

A Rational Use of Clozapine Based on Adverse Drug Reactions, Pharmacokinetics, and Clinical Pharmacopsychology

Using Richardson and Davidson's model and the sciences of pharmacokinetics and clinical pharmacopsychology, this article reviewed the: (1) poor life expectancy associated with treatment-resistant schizophrenia (TRS), which may be improved in patients who adhere to clozapine; (2) findings that clozapine is the best treatment for TRS (according to efficacy, effectiveness and well-being); and (3) potential for clozapine to cause vulnerabilities, including potentially lethal adverse drug reactions such as agranulocytosis, pneumonia, and myocarditis. Rational use requires: (1) modification of the clozapine package insert worldwide to include lower doses for Asians and to avoid the lethality associated with pneumonia, (2) the use of clozapine levels for personalizing dosing, and (3) the use of slow and personalized titration. This may make clozapine as safe as possible and contribute to increased life expectancy and well-being. In the absence of data on COVID-19 in clozapine patients, clozapine possibly impairs immunological mechanisms and may increase pneumonia risk in infected patients. Psychiatrists should call their clozapine patients and families and explain to them that if the patient develops fever or flu-like symptoms, the psychiatrist should be called and should consider halving the clozapine dose. If the patient is hospitalized with pneumonia, the treating physician needs to assess for symptoms of clozapine intoxication since halving the dose may not be enough for all patients; consider decreasing it to one-third or even stopping it. Once the signs of inflammation and fever have disappeared, the clozapine dose can be slowly increased to the prior dosage level.

Activation of Astroglial Connexin is Involved in Concentration-Dependent Double-Edged Sword Clinical Action of Clozapine

Clozapine (CLZ) is a gold-standard antipsychotic against treatment-refractory schizophrenia, but is one of the most toxic antipsychotic agents. Pharmacological mechanisms of the double-edged sword clinical action of CLZ remain to be clarified. To explore the mechanisms of CLZ, the present study determined the astroglial transmission associated with connexin43 (Cx43), which is the most principal expression in astrocytes and myocardial cells, and expression of Cx43 in primary cultured astrocytes. Both acute and subchronic administrations of CLZ concentration-dependently increased Cx43-associated astroglial release of l-glutamate and d-serine, whereas therapeutic-relevant concentration of CLZ acutely did not affect but subchronically increased astroglial release. In contrast, after the subchronic administration of therapeutic-relevant concentration of valproate (VPA), acute administration of therapeutic-relevant concentration of CLZ drastically increased Cx43-associated astroglial releases. VPA increased Cx43 expression in cytosol fraction without affecting plasma membrane fraction, whereas CLZ increased Cx43 expression in both fractions. Acute administration of therapeutic-relevant concentration of CLZ drastically increased Cx43 expression in the plasma membrane fraction of astrocytes subchronically treated with VPA. The present findings suggest that CLZ-induced the activation of Cx43-associated channel activity and transported Cx43 to plasma membrane, probably contribute to the double-edged sword clinical action of CLZ, such as improvement of cognitive dysfunction and CLZ-induced myocarditis.

Demographic and clinical features as predictors of clozapine response in patients with schizophrenia spectrum disorders: A systematic review and meta-analysis

OBJECTIVES

Clozapine (CLZ) is prescribed to (relatively) treatment-resistant patients with schizophrenia spectrum disorders. Currently, it is unknown what factors predict response to CLZ. Therefore, we performed meta-analyses to identify predictors of CLZ response, hence aiming to facilitate timely and efficient prescribing of CLZ.

METHODS

A systematic search was performed in 'Pubmed' and 'Embase' until 1 January 2019. Articles were eligible if they provided data on predictors of CLZ response measured demographic and clinical factors at baseline or biochemical factors at follow-up in schizophrenia spectrum disorder patients.

RESULTS

A total of 34 articles, total number of participants = 9386; N unique = 2094, were eligible. Factors significantly associated with better CLZ response were: lower age, lower PANSS negative score and paranoid schizophrenia subtype.

CONCLUSION

The results of our meta-analyses suggest that three baseline demographic and clinical features are associated with better clozapine response, i.e. relatively young age, few negative symptoms and paranoid schizophrenia subtype. These variables may be taken into account by clinicians who consider treating a specific patient with CLZ.

Clozapine Normalizes a Glutamatergic Transmission Abnormality Induced by an Impaired NMDA Receptor in the Thalamocortical Pathway via the Activation of a Group III Metabotropic Glutamate Receptor

Pharmacological mechanisms of gold-standard antipsychotics against treatment-refractory schizophrenia, such as clozapine (CLZ), remain unclear. We aimed to explore the mechanisms of CLZ by investigating the effects of MK801 and CLZ on tripartite synaptic transmission in the thalamocortical glutamatergic pathway using multi-probe microdialysis and primary cultured astrocytes. l-glutamate release in the medial prefrontal cortex (mPFC) was unaffected by local MK801 administration into mPFC but was enhanced in the mediodorsal thalamic nucleus (MDTN) and reticular thalamic nucleus (RTN) via GABAergic disinhibition in the RTN–MDTN pathway. The local administration of therapeutically relevant concentrations of CLZ into mPFC and MDTN increased and did not affect mPFC l-glutamate release. The local administration of the therapeutically relevant concentration of CLZ into mPFC reduced MK801-induced mPFC l-glutamate release via presynaptic group III metabotropic glutamate receptor (III-mGluR) activation. However, toxic concentrations of CLZ activated l-glutamate release associated with hemichannels. This study demonstrated that RTN is a candidate generator region in which impaired N-methyl-d-aspartate (NMDA)/glutamate receptors likely produce thalamocortical hyperglutamatergic transmission. Additionally, we identified several mechanisms of CLZ relating to its superiority in treatment-resistant schizophrenia and its severe adverse effects: (1) the prevention of thalamocortical hyperglutamatergic transmission via activation of mPFC presynaptic III-mGluR and (2) activation of astroglial l-glutamate release associated with hemichannels. These actions may contribute to the unique clinical profile of CLZ.

Clozapine Metabolism in East Asians and Caucasians: A Pilot Exploration of the Prevalence of Poor Metabolizers and a Systematic Review

PURPOSE/BACKGROUND

In clozapine therapeutic drug monitoring (TDM) studies, Chinese reached the same concentrations using half the dosage Caucasians use. Defining clozapine poor metabolizers (PMs) requires stratification by ethnicity, smoking, and sex.

METHODS/PROCEDURES

After sex and smoking stratification in 129 Chinese inpatients (mean, 8.8 TDM samples per patient), we explored the association between the total concentration-dose (C/D) ratio and CYP1A2 (*1C, *1F, and *7) and CYP2C19 alleles (*2 and *3). A systematic literature review identified 22 clozapine TDM prior studies (13 in Caucasians and 7 in East Asians).

FINDINGS/RESULTS

In our Chinese sample, the mean total clozapine C/D ratio (ng/mL per mg/d) was 1.96 for 22 male smokers, 2.07 for 5 female smokers, 2.47 for 36 male nonsmokers, and 2.95 for 66 female nonsmokers. CYP1A2 *1C had no significant effects, and CYP1A2 *1F had small effects. Five clozapine PMs (4%) needed low clozapine doses of 75 to 115 mg/d to get therapeutic concentrations. Using the same methodology in a published Italian sample, we found 5 PMs (3.3% of 152). In the systematic review, the clozapine C/D ratio (ng/mL per mg/d) was higher when comparing: (1) weighted mean values of 1.57 in 876 East Asians versus 1.07 in 1147 Caucasians and (2) ranks of 8 East Asians versus 13 Caucasian samples (P < 0.001).

IMPLICATIONS/CONCLUSIONS

Future TDM studies need to further explore the frequency of clozapine PMs after sex and smoking stratification in East Asian and Caucasian patients. Compared with Caucasians, East Asians appear to have a clinically relevant decrease in clozapine clearance.

Cigarette smoking has a differential effect on the plasma level of clozapine in Taiwanese schizophrenic patients associated with the CYP1A2 gene -163A/C single nucleotide polymorphism

OBJECTIVE

The efficacy of clozapine clearance has been shown to be associated with smoking and genetic polymorphism of CYP1A2. This study aims to investigate the effect of smoking on the plasma level of clozapine in Taiwanese schizophrenic patients and its relevance to the CYP1A2 gene -163A/C single nucleotide polymorphism.

MATERIALS AND METHODS

A total of 143 hospitalized schizophrenic patients who had received clozapine therapy for at least 14 days were enrolled in this study. The trough plasma concentration of clozapine was measured with LC/MS/MS. The -163A/C variant in the CYP1A2 gene was identified by DNA sequencing and restriction fragment length polymorphism analysis. The effect of smoking on the clozapine level was examined by multiple linear regression analysis and its relation to the -163A/C variant of the CYP1A2 gene was analyzed using a general linear model with Bonferroni correction.

RESULTS

Patients with smoking habits showed a significantly lower plasma level of clozapine than those without smoking habits (P=0.022) and the difference in clozapine levels between smokers and nonsmokers appeared to be significant in the individuals carrying the homozygous -163A allele (P=0.02). It was also found that nonsmokers carrying the -163A allele tended to have higher plasma levels of clozapine. This tendency was not found in the individuals with smoking habits.

CONCLUSION

Cigarette smoking has a significant impact on the plasma level of clozapine in Taiwanese schizophrenic patients carrying the homozygous -163A allele in the CYP1A2 gene. Cigarette smoking may increase the clearance of clozapine in these patients.

Factors associated with subjective side-effects during clozapine treatment

OBJECTIVE

Clozapine is associated with subjectively unpleasant or clinically serious side-effects, which may affect treatment adherence. The aims of the study were to explore the association of clozapine+ norclozapine serum concentration and other factors with subjective side-effects in schizophrenia patients.

METHODS

In this cross-sectional study, 237 patients with a diagnosis of schizophrenia, schizo-affective or other non-organic psychoses completed the Liverpool University Neuroleptic Side Effect Rating Scale (LUNSERS), a self-report scale measuring side-effects of antipsychotics and a clinical questionnaire. Clozapine+ norclozapine serum concentration of 190 patients was measured. Of the patients 80 (33.7%) were on antipsychotic combination therapy.

RESULTS

Higher clozapine+ norclozapine concentrations were associated with the depression-anxiety factor of LUNSERS and antipsychotic combination treatments were associated with sympatichotonia-tension factor. Younger patients reported sedation more often than older patients.

CONCLUSION

According to the present results, high clozapine concentrations were associated with depression-anxiety symptoms, but the causality remains unknown.

A review on schizophrenia and relapse--a quest for user-friendly psychopharmacotherapy

OBJECTIVE

Schizophrenia in general is notoriously associated with relapses rendering the illness progressive to worse outcomes, a concept of which is compatible with neurotoxicity. Therefore, relapse prevention is of utmost clinical relevance.

METHODS

In this review, we aim to put relapse into clinical context in the realm of natural history of, or heterogeneity in, schizophrenia and summarize risk factors of relapse. We discuss how to effectively 'define' relapse in schizophrenia and recent meta-analytic studies on this topic to highlight the importance of continuous antipsychotic treatment.

RESULTS

The following issues emerged: 'How low maintenance antipsychotic dosage could be?’, 'How extended dosing could be?’, 'Who could be successfully withdrawn from antipsychotics?’ and 'How relapse could be defined in the first place?’ The question in particular is how better to deliver antipsychotics at the lowest possible, whereby dose and dosing interval are relevant. While ongoing antipsychotic treatment is the rule, recent works are pointing to a possibility of lower dosage in the maintenance phase of the illness.

CONCLUSIONS

Bearing in mind that suboptimal adherence and withdrawal from antipsychotics are an established and unequivocal risk factor for relapse, further investigations are certainly needed to explore user-friendly manner of psychopharmacotherapy to prevent relapse in schizophrenia.

Systematic review of long-acting injectables versus oral atypical antipsychotics on hospitalization in schizophrenia

OBJECTIVE

To assess the impact of long-acting injectables (LAIs) versus oral antipsychotics (OAs) on hospitalizations among patients with schizophrenia by conducting a systematic literature review of studies with different study designs and performing a meta-analysis.

METHODS

Using the PubMed database and major psychiatric conference proceedings, a systematic literature review for January 2000 to July 2013 was performed to identify English-language studies evaluating schizophrenia patients treated with atypical antipsychotics. Studies reporting hospitalization rates as a percentage of patients hospitalized or as the number of hospitalizations per person per year were selected. The primary meta-analysis assessed the percentage decrease in hospitalization rates before and after treatment initiation for matched time periods. The secondary meta-analysis assessed the absolute rate of hospitalization during follow-up. Pooled treatment-effect estimates were calculated using random-effects models. To account for differences in patient and study-level characteristics between studies, meta-regression analyses were used. Subset analyses further explored the heterogeneity across study designs.

RESULTS

Fifty-eight studies evaluating 25 arms (LAIs: 13 arms, 4516 patients; OAs: 12 arms, 23,516 patients) in the primary meta-analysis and 78 arms (LAIs: 12 arms, 4481 patients; OAs: 66 arms, 96,230 patients) in the secondary meta-analysis were identified. Reduction in hospitalization rates for LAIs was 20.7 percentage points higher than that of OAs (random-effects estimates: LAIs = 56.2% vs. OAs = 35.5%, P = 0.023). Controlling for patient and study characteristics, the adjusted percentage reduction in hospitalization rates for LAIs was 26.4 percentage points higher than for OAs (95% CI: 3.3-49.5, P = 0.027). As for the secondary meta-analysis, no significant difference between LAIs and OAs was observed (random-effects estimate: -8.6, 95% CI: -18.1-1.0, P = 0.077). Subset analyses across type of study yielded consistent results. Limitations of this analysis include the long observation period, which may not reflect current treatment patterns, the use of all-cause hospitalization, which may not be solely related to schizophrenia, and the fact that most studies in the LAI cohort evaluated risperidone.

CONCLUSION

The primary results of this meta-analysis, including studies with both interventional and non-interventional designs and using meta-regressions, suggest that LAIs are associated with higher reductions in hospitalization rates for schizophrenia patients compared to OAs.

Definitions and drivers of relapse in patients with schizophrenia: a systematic literature review

Relapse in patients with schizophrenia has devastating repercussions, including worsening symptoms, impaired functioning, cognitive deterioration and reduced quality of life. This progressive decline exacerbates the burden of illness on patients and their families. Relapse prevention is identified as a key therapeutic aim; however, the absence of widely accepted relapse definition criteria considerably hampers achieving this goal. We conducted a literature review in order to investigate the reporting of relapses and the validity of hospitalization as a proxy for relapse in patients with schizophrenia. The primary aim was to assess the range and validity of methods used to define relapse in observational or naturalistic settings. The secondary aim was to capture information on factors that predicted or influenced the risk of relapse. A structured search of the PubMed database identified articles that discussed relapse, and hospitalization as a proxy of relapse, in patients with schizophrenia. National and international guidelines were also reviewed. Of the 150 publications and guidelines identified, 87 defined relapse and 62% of these discussed hospitalization. Where hospitalization was discussed, this was as a proxy for, or a component of, relapse in the majority of cases. However, hospitalization duration and type varied and were not always well defined. Scales were used to define relapse in 53 instances; 10 different scales were used and multiple scales often appeared within the same definition. There were 95 references to factors that may drive relapse, including non-adherence to antipsychotic medication (21/95), stress/depression (11/95) and substance abuse (9/95). Twenty-five publications discussed the potential of antipsychotic therapy to reduce relapse rates-continuous antipsychotic therapy was associated with reduced frequency and duration of hospitalization. Non-pharmacological interventions, such as psychoeducation and cognitive behavioural therapy, were also commonly reported as factors that may reduce relapse. In conclusion, this review identified numerous factors used to define relapse. Hospitalization was the factor most frequently used and represents a useful proxy for relapse when reporting in a naturalistic setting. Several factors were reported to increase the risk of relapse, and observation of these may aid the identification of at-risk patients.

A review of the use of clozapine levels to guide treatment and determine cause of death

OBJECTIVE

To review the literature to examine the use of clozapine levels to (i) guide therapy and prevent toxicity in clinical care and (ii) determine cause of death in post-mortem examination of patients who were treated with clozapine.

METHODS

MEDLINE was searched in December 2010 using the following keywords: 'clozapine levels', 'clozapine and toxicity', 'clozapine and death', 'clozapine and mortality' and 'post-mortem redistribution'. Data was also collected from the 2010 MIMS Annual.

RESULTS

The literature reported significant variation in clozapine levels attained with any given dose, and considerable variability in the clinical response achieved at any given clozapine level. The lowest effective clozapine levels ranged from 250 to 550 µg/L, while the recommended upper limit to prevent toxicity varied from 600 to 2000 µg/L. There was minimal correlation between clozapine levels and side effects, with the exception of sedation, hypotension and seizure activity. The risk of seizures increased with plasma clozapine levels greater than 600 µg/L or rapid upward titration. In addition to prescribed dose, there are many factors that influence plasma clozapine levels. After death, the process of post-mortem drug redistribution resulted in 3.00 to 4.89 times increases in clozapine levels in central blood vessels and 1.5 fold increases in peripheral vessels compared to ante-mortem levels.

CONCLUSIONS

The exact range of clozapine levels that corresponds to toxicity remains unclear. However, levels between 350 µg/L and 1000 µg/L achieved with gradual upward titration are more likely to be effective and less likely to cause toxicity. Ongoing clozapine level monitoring is indicated, especially when (i) prescribing higher doses (> 600 mg/day) of clozapine, (ii) there has been a change in a patient's concomitant pharmacotherapy or cigarette use and (iii) there has been a suboptimal response to treatment. The use of post-mortem clozapine levels to determine clozapine toxicity as a cause of death is unreliable.

A gene expression and systems pathway analysis of the effects of clozapine compared to haloperidol in the mouse brain implicates susceptibility genes for schizophrenia

Clozapine has markedly superior clinical properties compared to other antipsychotic drugs but the side effects of agranulocytosis, weight gain and diabetes limit its use. The reason why clozapine is more effective is not well understood. We studied messenger RNA (mRNA) gene expression in the mouse brain to identify pathways changed by clozapine compared to those changed by haloperidol so that we could identify which changes were specific to clozapine. Data interpretation was performed using an over-representation analysis (ORA) of gene ontology (GO), pathways and gene-by-gene differences. Clozapine significantly changed gene expression in pathways related to neuronal growth and differentiation to a greater extent than haloperidol; including the microtubule-associated protein kinase (MAPK) signalling and GO terms related to axonogenesis and neuroblast proliferation. Several genes implicated genetically or functionally in schizophrenia such as frizzled homolog 3 (FZD3), U2AF homology motif kinase 1 (UHMK1), pericentriolar material 1 (PCM1) and brain-derived neurotrophic factor (BDNF) were changed by clozapine but not by haloperidol. Furthermore, when compared to untreated controls clozapine specifically regulated transcripts related to the glutamate system, microtubule function, presynaptic proteins and pathways associated with synaptic transmission such as clathrin cage assembly. Compared to untreated controls haloperidol modulated expression of neurotoxic and apoptotic responses such as NF-kappa B and caspase pathways, whilst clozapine did not. Pathways involving lipid and carbohydrate metabolism and appetite regulation were also more affected by clozapine than by haloperidol.

Glutamatergic changes in the cerebral white matter associated with schizophrenic exacerbation

OBJECTIVE

Glutamatergic dysfunction in the brain has been implicated in the pathophysiology of schizophrenia. This study was aimed to examine several brain chemical mediators, including Glx (glutamate + glutamine), using (1)H magnetic resonance spectroscopy (MRS) in medicated patients with schizophrenia, with and without psychotic exacerbation.

METHOD

(1)H MRS was acquired in 24 patients with schizophrenia, with psychotic exacerbation; 22 patients without exacerbation; and 27 age- and sex-matched healthy volunteers. The levels of metabolites were measured in the left frontal and inferior parietal white matter and compared across the three groups.

RESULTS

The Glx level was significantly elevated in the left inferior parietal white matter in the patients with psychotic exacerbation in comparison with that in the healthy volunteers and the patients without exacerbation (P < 0.05). We also detected that there was a significant correlation between Positive and Negative Syndrome Scale-positive scale and Glx level in the left parietal white matter (r = 0.51, P < 0.001).

CONCLUSION

Higher than normal Glx levels indicate glutamatergic overactivity in the left inferior parietal white matter with schizophrenic exacerbation, a finding that is in accordance with the glutamatergic hypothesis in schizophrenia. The Glx level measured by (1)H MRS could be a biomarker for exacerbation in schizophrenia.

Plasma clozapine, norclozapine, and the clozapine:norclozapine ratio in relation to prescribed dose and other factors: data from a therapeutic drug monitoring service, 1993-2007

Therapeutic drug monitoring of plasma clozapine and of its principal plasma metabolite N-desmethylclozapine (norclozapine) (predose or "trough" sample) can help in monitoring adherence, in dose adjustment, and in minimizing the risk of toxicity. To obtain data to assist in the interpretation of analytical results, the results from a clozapine therapeutic drug monitoring service, 1993-2007, have been audited. There were 104,127 samples from 26,796 patients [18,750 (70%) men aged at time of first sample (median, range) 34 (10-89) years, and 7763 (30%) female aged 38 (12-90) years]. Clozapine was not detected (plasma concentration <0.01 mg/L) in 1.5% of samples (prescribed clozapine dose up to 900 mg/d). Plasma clozapine was either below 0.35 mg/L or greater than 0.60 mg/L in 42.5% and 28.4% of samples, respectively; in 0.4% samples plasma clozapine was 2.0 mg/L or more. Although plasma clozapine was broadly related to prescribed dose, there was much variation: 1.2% of samples had plasma clozapine >1.0 mg/L at prescribed clozapine doses up to 150 mg/d (76.2% < 0.35 mg/L), whereas 23.3% of samples had plasma clozapine < 0.35 mg/L at doses of 850 mg/d and over (18.0% > 1.0 mg/L). The highest plasma clozapine and norclozapine concentrations encountered were 4.95 and 2.45 mg/L, respectively. Although the median plasma clozapine:norclozapine ratio was 1.25 at plasma clozapine concentrations < 0.35 mg/L, the median ratio was 2.08 at plasma clozapine concentrations > 1.0 mg/L. Data (median, 10th-90th percentile) for both clozapine and norclozapine by prescribed clozapine dose band are useful in assessing partial adherence. Analysis of the plasma clozapine:norclozapine ratio by clozapine concentration provides clear evidence that clozapine N-demethylation becomes saturated at higher plasma clozapine concentrations and adds urgency to the requirement for dose adjustment should smoking habit change. A clozapine:norclozapine ratio greater then 2 suggests either a nontrough sample, or that clozapine N-demethylation has become saturated.

Efficacy and tolerability of ziprasidone versus risperidone as augmentation in patients partially responsive to clozapine: a randomised controlled clinical trial

Patients suffering from schizophrenic psychoses sometimes insufficiently respond to antipsychotic monotherapy and then combination approaches are preferred. We aimed in validating the add-on of ziprasidone and risperidone to clozapine, and we performed a randomised head-to-head trial. Patients with partial response to clozapine were randomly attributed to augmentation with ziprasidone (n = 12) or risperidone (n = 12). Efficacy assessments included the Positive and Negative Syndrome Scale (PANSS), the Scale for the Assessment of Negative Symptoms (SANS), the Hamilton Depression Scale (HAMD), the Clinical Global Impression (CGI) and the Global Assessment of Functioning (GAF). Furthermore, several safety and tolerability measures were obtained. After six weeks, both groups showed significant reductions of positive and negative symptoms. In addition, affective state, psychosocial functioning and clozapine side effects improved without significant differences between the groups. Both approaches were well tolerated. However, the ziprasidone group experienced a small elongation of the QTc interval and a reduction of extrapyramidal symptoms. Patients under clozapine-risperidone therapy developed a rise of serum prolactin levels. The clozapine augmentation with ziprasidone or risperidone resulted in significant psychopathological improvements. The side effects differed between the treatment groups. Further head-to-head comparisons of atypical antipsychotics as add-on to clozapine are necessary.

Hemoperfusion in the treatment of acute clozapine intoxication in China

BACKGROUND AND AIMS

No systematic study has focused on the characteristics and outcome of acute clozapine intoxication, although clozapine is the most widely used antipsychotic agent in China. The study reported herein examined the features of clozapine intoxication and the therapeutic effect of hemoperfusion (HP).

METHODS

In a retrospective chart review, the notes of 47 patients who attempted suicide by ingesting large amounts of clozapine and were treated at the only psychiatric emergency service in Beijing were analyzed. Of the 20 unconscious patients with plasma clozapine concentrations of more than 2000 ng/mL, 14 received a combination of HP and symptomatic treatment, whereas the other 6 and the remaining 27 patients received only symptomatic treatment. Patients' psychiatric conditions and both plasma clozapine and norclozapine concentrations were closely monitored and registered.

RESULTS

One patient died of pulmonary edema and subsequent heart failure, but the rest of the patients recovered without any sequelae. Patients who received HP regained consciousness significantly faster than their counterparts with the same level of clozapine plasma concentration (>2000 ng/mL) who did not receive HP.

CONCLUSIONS

A combination of HP and symptomatic treatment is the best therapeutic option when plasma clozapine concentration is high.

Prevalence and nature of side effects during clozapine maintenance treatment and the relationship with clozapine dose and plasma concentration

Clozapine is associated with non-neurological side effects that can be subjectively unpleasant and/or clinically serious. We sought to: (i) assess the nature and prevalence of side effects experienced by patients receiving maintenance treatment with clozapine and (ii) explore the relationship between clozapine plasma concentration and side effect burden. Patients were receiving clozapine maintenance treatment. Open questioning followed by systematic enquiry using the Antipsychotic Non-neurological Side Effects Rating Scale were used to assess side effects. Trough plasma clozapine and norclozapine concentrations were measured. One hundred and three patients participated. On open questioning, 61 patients reported a total of 117 side effects, whereas systematic enquiry identified an additional 649 side effects, with each patient reporting at least one. Clozapine plasma concentrations were significantly but weakly correlated with total Antipsychotic Non-neurological Side Effects Rating Scale score (Pearson correlation=0.29, P<0.004). Patients with a plasma clozapine concentration >0.25 mg/l were significantly more likely to have moderate/severe side effects than patients with lower plasma concentrations (63/76 vs. 12/23, chi=9.07, d.f.=1, P<0.01). The side-effect burden associated with maintenance clozapine treatment is high and the true extent can only be ascertained by systematic inquiry. The use of target plasma concentrations below those used for acute treatment should be explored as a strategy for minimizing side effects.