Clozapine rechallenge and initiation despite neutropenia- a practical, step-by-step guide

Overcoming the barriers to identifying and managing treatment-resistant schizophrenia and to improving access to clozapine: A narrative review and recommendation for clinical practice

Clozapine is the only approved antipsychotic for treatment-resistant schizophrenia (TRS). Although a large body of evidence supports its efficacy and favorable risk-benefit ratio in individuals who have failed two or more antipsychotics, clozapine remains underused. However, variations in clozapine utilization across geographic and clinical settings suggest that it could be possible to improve its use. In this narrative review and expert opinion, we summarized information available in the literature on the mechanisms of action, effectiveness, and potential adverse events of clozapine. We identified barriers leading to discouragement in clozapine prescription internationally, and we proposed practical solutions to overcome each barrier. One of the main obstacles identified to the use of clozapine is the lack of appropriate training for physicians: we highlighted the need to develop specific professional programs to train clinicians, both practicing and in residency, on the relevance and efficacy of clozapine in TRS treatment, initiation, maintenance, and management of potential adverse events. This approach would facilitate physicians to identify eligible patients and offer clozapine as a treatment option in the early stage of the disease. We also noted that increasing awareness of the benefits of clozapine among healthcare professionals, people with TRS, and their caregivers can help promote the use of clozapine. Educational material, such as leaflets or videos, could be developed and distributed to achieve this goal. The information provided in this article may be useful to improve disease burden and support healthcare professionals, patients, and caregivers navigating the complex pathways to TRS management.

Understanding clozapine-related blood dyscrasias. Developments, genetics, ethnicity and disparity: it's a CIN

Clozapine remains the gold standard intervention for treatment-resistant schizophrenia; however, it remains underused, especially for some minority groups. A significant impediment is concern about propensity to neutropenia. The aim of this article is to provide an update on current knowledge relating to: the pattern and incidence of severe blood dyscrasias; the effectiveness of current monitoring regimes in reducing harm; the mechanisms of and the distinctions between clozapine-induced neutropenia and agranulocytosis; benign ethnic neutropenia; and changes to the monitoring thresholds in the USA and other international variations. These all have implications for the practical use of clozapine; specifically, how barriers to initiating, maintaining and restarting clozapine can be understood and in many cases overcome, especially for patients from minority groups, potentially with simpler approaches than the use of lithium or G-CSF.

Risks and benefits of clozapine and lithium co-prescribing: A systematic review and expert recommendations

OBJECTIVES

To identify the risks and benefits of clozapine‑lithium co-prescription.

METHODS

Articles published in English or French were identified with a MEDLINE, Web of Sciences and PsycINFO search, from inception through January 2023, using the term 'clozapine' in combination with 'lithium'. Data were synthesized narratively.

RESULTS

Of the 67 articles included in the review, more than half (n = 38, 56.7 %) were focused on clozapine-related blood dyscrasia. A body of evidence drawn from case reports and retrospective chart studies highlights the potential benefits of lithium prescription for clozapine-related neutropenia, since this strategy may avoid clozapine discontinuation or allow its rechallenge. The most documented adverse drug reactions (ADRs) associated with clozapine‑lithium co-prescription are neurotoxic events, which may be prevented or detected early by clinical, electroencephalographic and therapeutic drug monitoring. Causality assessment cannot be established for other reported ADRs occurring during clozapine‑lithium co-prescription. The benefits of the combined prescription on psychotic and/or mood symptoms are poorly documented.

CONCLUSION

The risks and benefits of clozapine‑lithium co-prescription require further exploration as the combination might significantly contribute to reducing underprescription or premature discontinuation of clozapine.

Risk of clozapine-associated agranulocytosis and mandatory white blood cell monitoring: Can the regulations be relaxed?

After the introduction of clozapine eight Finnish patients died after developing agranulocytosis. Clozapine was withdrawn from the market and only reintroduced with strict mandatory white blood cell monitoring as long as treatment lasts and thresholds at which clozapine must be discontinued definitively. The fear of agranulocytosis and the need for intensive blood monitoring is the single most important barrier for prescribers and patients alike and leads to underprescription of the only effective and approved medication for treatment-resistant schizophrenia. We summarize evidence that the risk of agranulocytosis is smaller than perceived at the time of reintroduction, is concentrated in the first 18 weeks of treatment, is not greater than with other antipsychotics thereafter and that frequent blood monitoring has not demonstrably decreased the rate of agranulocytosis. Therefore we propose 1) mandatory monitoring of the absolute neutrophil count (ANC) exclusively during the first 18 weeks of clozapine treatment, 2) that thereafter the prescriber and the well-informed patient decide together about further monitoring frequency, 3) that clozapine treatment must be stopped if the ANC falls below 1.0 × 109/L. Continuation of clozapine or a rechallenge are possible if prescriber and patient determine that the benefits outweigh the risks. 4) National registries which control the haematologic monitoring are unnecessary and do not help to reduce clozapine-induced agranulocytosis. They should at least be restricted to the first 18 weeks of clozapine use.

Successful Clozapine Rechallenge After Clozapine-Induced Severe Anemia: A Case Report

INTRODUCTION

Clozapine, a second-generation antipsychotic (SGA), is considered the gold standard medication to treat patients with treatment-resistant schizophrenia (TRS). Despite its efficacy, clozapine is associated with adverse effects, notably neutropenia and agranulocytosis. Other hematological adverse effects are less common. Severe anemia is a rare adverse effect seldom reported in the literature and is typically associated with pure red cell aplasia (PRCA). Nevertheless, the benefits of clozapine in managing TRS make rechallenge a reasonable option.

CASE REPORT

We present the case of a 35-year-old man with TRS, resistant to previous antipsychotics, who experienced severe anemia during clozapine treatment. An investigation for clozapine-induced anemia revealed PRCA on myelogram. After discontinuing clozapine, the patient's hemoglobin levels recovered. Subsequent treatments with olanzapine, zuclopenthixol, and aripiprazole proved ineffective, leading us to consider a clozapine rechallenge. The rechallenge, monitored for 58 days, resulted in improved psychiatric symptoms and stable hemoglobin levels. The patient remained stable during 6 months of follow-up, with no hematological changes.

DISCUSSION

PRCA is a very rare adverse effect of clozapine. The cause of drug-induced PRCA is still unknown; for clozapine, there are no studies. Rechallenge after a severe and rare adverse effect is a complex decision. This case is the first to report a successful clozapine rechallenge following severe anemia without other blood dyscrasias, emphasizing the imperative need for close monitoring during the rechallenge process. Further study is warranted to understand the predictive factors for a successful outcome in clozapine rechallenges.

Evaluating Monitoring Guidelines of Clozapine-Induced Adverse Effects: a Systematic Review

BACKGROUND AND OBJECTIVES

Despite the evidence that no other antipsychotic is effective as clozapine for the treatment of resistant schizophrenia, it is associated with various metabolic, neuroendocrine, cardiovascular, and gastrointestinal adverse effects. Guidelines aiming to address the monitoring of clozapine's (serious) adverse effects can be helpful to prevent and treat these effects. However, many of these guidelines seem to lack one or more important monitoring recommendations. We aimed to systematically review the content and quality of existing monitoring guidelines/recommendations for clozapine-induced adverse effects.

METHODS

A comprehensive and systematic literature search, using the MEDLINE, Embase, Web of Science, and Cochrane databases, was conducted for guidelines/recommendations on the monitoring of clozapine-induced adverse events, published between January 2004 and April 2023 (last search 16 April 2023). Only peer-reviewed published guidelines reporting on the comprehensive monitoring of all major clozapine-induced adverse effects and including evidence-based recommendations, developed after the year 2004, were included. Studies reporting on the monitoring of adverse effects of clozapine without being a formal guideline, guidelines reporting on the monitoring of one or a limited number of adverse effects of clozapine, guidelines that were not peer reviewed or published, expert opinion papers without formal consensus guideline development, or guidelines developed before the year 2004, were excluded. The Appraisal of Guidelines for Research and Evaluation II (AGREE-II) tool was used to evaluate the guidelines/recommendations' quality.

RESULTS

Only one guideline met the inclusion criteria. This consensus statement made recommendations for hematological monitoring, and the monitoring of metabolic, cardiac, and three other adverse effects. Highest scores for the qualitative assessment were found for the domains "scope and purpose" (66.7%), "clarity of presentation" (44.4%), and "editorial independence" (66.7%). Lowest scores were found for "rigor of development" (14.6%) and "applicability" (0%).

CONCLUSIONS

Future guidelines should develop more comprehensive recommendations about specific clozapine-induced adverse effects, including constipation, myocarditis, tachycardia, and seizures, as well as include a rechallenge policy. There is an urgent need for well-developed, methodologically stringent, guidelines.

REGISTRATION

PROSPERO registration number, CRD42023402480.

Clozapine-induced eosinophilia: A case report

Schizophrenia is a chronic neuropsychiatric illness defined by the appearance of positive, and negative symptoms and/or cognitive impairment. Antipsychotic drugs are predominantly used in the treatment of psychotic disorders, but not all patients with schizophrenia respond to every antipsychotic medication. Clozapine is one of the best atypical antipsychotics and is highly effective in treating treatment-resistant schizophrenia. Evidence suggests that clozapine appears to be effective in lowering the risk of suicide, extrapyramidal side effects, and relapse in patients with schizophrenia. Per contra, clozapine is not the first-line treatment due to its unalterable aftereffects such as agranulocytosis, metabolic syndrome, seizures, and rarely, eosinophilia. Eosinophilia can be life-threatening. Eosinophils infiltrate different tissues and cause inflammation in multiple organs causing end-organ damage. The current study aimed to report the incidence of eosinophilia associated with clozapine use in patients with schizophrenia. Literature on clozapine-induced eosinophilia is relatively scarce. Understanding the progression and management of clozapine-induced eosinophilia and its end-organ effects is imperative. While there is insufficient data about the guidelines in the management of clozapine-induced eosinophilia, this study contributes to understanding the patterns of the disease progression with clozapine dosage. A case study was done on a patient with schizophrenia and autistic spectrum disorder who was on clozapine. Data on how eosinophil levels varied with clozapine dosing was analyzed and documented. The evidence of clozapine dosage affecting eosinophil and C-reactive protein levels in this patient was summarized in a table and a narrative review.

Pharmacological Strategies for Bipolar Disorders in Acute Phases and Chronic Management with a Special Focus on Lithium, Valproic Acid, and Atypical Antipsychotics

Bipolar disorders (BDs) are a heterogeneous group of severe affective disorders generally described by the alternation of (hypo)manic, depressive, and mixed phases, with euthymic intervals of variable duration. BDs are burdened with high psychiatric and physical comorbidity, increased suicide risk and reduced life expectancy. In addition, BDs can progress into complicated forms (e.g., mixed states, rapid/irregular cycling), which are more difficult to treat and often require personalized pharmacological combinations. Mood stabilizers, particularly Lithium and Valproic acid (VPA), still represent the cornerstones of both acute and chronic pharmacotherapies of BDs. Lithium is the gold standard in BD-I and BDII with typical features, while VPA seems more effective for atypical forms (e.g., mixed-prevalence and rapid-cycling). However, despite appropriate mood stabilization, many patients show residual symptoms, and more than a half recur within 1-2 years, highlighting the need of additional strategies. Among these, the association of atypical antipsychotics (AAPs) with mood stabilizers is recurrent in the treatment of acute phases, but it is also being growingly explored in the maintenance pharmacotherapy. These combinations are clinically more aggressive and often needed in the acute phases, whereas simplifying pharmacotherapies to mood stabilizers only is preferable in the long-term, whenever possible. When mood stabilizers are not enough for maintenance treatment, Quetiapine and, less consistently, Aripiprazole have been proposed as the most advisable adjunctive strategies, for their safety and tolerability profiles. However, in view of the increased risk of serious adverse effects, a careful patient-centered balance between costs and benefits is mandatory.

Second to none: rationale, timing, and clinical management of clozapine use in schizophrenia

Despite its enduring relevance as the single most effective and important evidence-based treatment for schizophrenia, underutilization of clozapine remains considerable. To a substantial degree, this is attributable to a reluctance of psychiatrists to offer clozapine due to its relatively large side-effect burden and the complexity of its use. This underscores the necessity for continued education regarding both the vital nature and the intricacies of clozapine treatment. This narrative review summarizes all clinically relevant areas of evidence, which support clozapine's wide-ranging superior efficacy - for treatment-resistant schizophrenia (TRS) and beyond - and make its safe use eminently feasible. Converging evidence indicates that TRS constitutes a distinct albeit heterogeneous subgroup of schizophrenias primarily responsive to clozapine. Most importantly, the predominantly early onset of treatment resistance and the considerable decline in response rates associated with its delayed initiation make clozapine an essential treatment option throughout the course of illness, beginning with the first psychotic episode. To maximize patients' benefits, systematic early recognition efforts based on stringent use of TRS criteria, a timely offer of clozapine, thorough side-effect screening and management as well as consistent use of therapeutic drug monitoring and established augmentation strategies for suboptimal responders are crucial. To minimize permanent all-cause discontinuation, re-challenges after neutropenia or myocarditis should be considered. Owing to clozapine's unique efficacy, comorbid conditions including substance use and most somatic disorders should not dissuade but rather encourage clinicians to consider clozapine. Moreover, treatment decisions need to be informed by the late onset of clozapine's full effects, which for reduced suicidality and mortality rates may not even be readily apparent. Overall, the singular extent of its efficacy combined with the high level of patient satisfaction continues to distinguish clozapine from all other available antipsychotics.

Clozapine haematological monitoring for neutropenia: a global perspective

AIMS

Clozapine is licensed for treatment-resistant psychosis and remains underutilised. This may berelated to the stringent haematological monitoring requirements that are mandatory in most countries. We aimed to compare guidelines internationally and develop a novel Stringency Index. We hypothesised that the most stringent countries would have increased healthcare costs and reduced prescription rates.

METHOD

We conducted a literature review and survey of guidelines internationally. Guideline identification involved a literature review and consultation with clinical academics. We focused on the haematological monitoring parameters, frequency and thresholds for discontinuation and rechallenge after suspected clozapine-induced neutropenia. In addition, indicators reflecting monitoring guideline stringency were scored and visualised using a choropleth map. We developed a Stringency Index with an international panel of clozapine experts, through a modified-Delphi-survey. The Stringency Index was compared to health expenditure per-capita and clozapine prescription per 100 000 persons.

RESULTS

One hundred twocountries were included, from Europe (n = 35), Asia (n = 24), Africa (n = 20), South America (n = 11), North America (n = 7) and Oceania and Australia (n = 5). Guidelines differed in frequency of haematological monitoring and discontinuation thresholds. Overall, 5% of included countries had explicit guidelines for clozapine-rechallenge and 40% explicitly prohibited clozapine-rechallenge. Furthermore, 7% of included countries had modified discontinuation thresholds for benign ethnic neutropenia. None of the guidelines specified how long haematological monitoring should continue. The most stringent guidelines were in Europe, and the least stringent were in Africa and South America. There was a positive association (r = 0.43, p < 0.001) between a country's Stringency Index and healthcare expenditure per capita.

CONCLUSIONS

Recommendations on how haematological function should be monitored in patients treated with clozapine vary considerably between countries. It would be useful to standardise guidelines on haematological monitoring worldwide.

A Guideline and Checklist for Initiating and Managing Clozapine Treatment in Patients with Treatment-Resistant Schizophrenia

Treatment-resistant schizophrenia (TRS) will affect about one in three patients with schizophrenia. Clozapine is the only treatment approved for TRS, and patients should be treated as soon as possible to improve their chances of achieving remission. Despite its effectiveness, concern over side effects, monitoring requirements, and inexperience with prescribing often result in long delays that can expose patients to unnecessary risks and compromise their chances of achieving favorable long-term outcomes. We critically reviewed the literature on clozapine use in TRS, focusing on guidelines, systematic reviews, and algorithms to identify strategies for improving clozapine safety and tolerability. Based on this, we have provided an overview of strategies to support early initiation of clozapine in patients with TRS based on the latest evidence and our clinical experience, and have summarized the key elements in a practical, evidence-based checklist for identifying and managing patients with TRS, with the aim of increasing confidence in prescribing and monitoring clozapine therapy.

Clozapine re-challenge and initiation following neutropenia: a review and case series of 14 patients in a high-secure forensic hospital

OBJECTIVE

Clozapine remains the most effective intervention for treatment resistant schizophrenia; however, its use is prohibited following neutropenias. We review neutrophil biology as applied to clozapine and describe the strategies to initiate clozapine following neutropenia used in a case series of 14 consecutive patients rechallenged in a United Kingdom (UK) high-secure psychiatric hospital. We examine outcomes including the use of seclusion and transfer.

METHODS

A case series of 14 male patients with treatment resistant schizophrenia treated with clozapine despite previous episodes of neutropenia between 2006 and 2015 is presented. Data were collected during 2015 and 2019. Using this routinely collected clinical data, we describe the patient characteristics, causes of neutropenia, the strategies used for rechallenging with clozapine and clinical outcomes.

RESULTS

Previous neutropenias were the result of benign ethnic neutropenia, clozapine, other medications and autoimmune-related. Our risk mitigation strategies included: granulocyte-colony stimulating factor (G-CSF), lithium and watch-and-wait. There were no serious adverse events; at follow up half of the patient's had improved sufficiently to transfer them to conditions of lesser security. There were dramatic reductions in the use of seclusion.

CONCLUSION

Even in this extreme group, clozapine can be safely and effectively re/initiated following neutropenias, resulting in marked benefits for patients. This requires careful planning based on an understanding of neutrophil biology and the aetiology of the specific episode of neutropenia.

Characterization of Clozapine-Responsive Human T Cells

Use of the atypical antipsychotic clozapine is associated with life-threatening agranulocytosis. The delayed onset and the association with HLA variants are characteristic of an immunological mechanism. The objective of this study was to generate clozapine-specific T cell clones (TCC) and characterize pathways of T cell activation and cross-reactivity with clozapine metabolites and olanzapine. TCC were established and characterized by culturing PBMCs from healthy donors and patients with a history of clozapine-induced agranulocytosis. Modeling was used to explore the drug-HLA binding interaction. Global TCC protein changes were profiled by mass spectrometry. Six well-growing clozapine-responsive CD4⁺ and CD8⁺ TCC were used for experiments; activation of TCC required APC, with clozapine interacting directly at therapeutic concentrations with several HLA-DR molecules. TCC were also activated with N-desmethylclozapine and olanzapine at supratherapeutic concentrations. Marked changes in TCC protein expression profiles were observed when clozapine treatment was compared with olanzapine and the medium control. Docking of the compounds into the HLA-DRB1*15:01 and HLA-DRB1*04:01 binding clefts revealed that clozapine and olanzapine bind in a similar conformation to the P4-P6 peptide binding pockets, whereas clozapine N-oxide, which did not activate the TCC, bound in a different conformation. TCC secreted Th1, Th2, and Th22 cytokines and effector molecules and expressed TCR Vβ 5.1, 16, 20, and 22 as well as chemokine receptors CXCR3, CCR6, CCR4, and CCR9. Collectively, these data show that clozapine interacts at therapeutic concentrations with HLA-DR molecules and activates human CD4⁺ T cells. Olanzapine only activates TCC at supratherapeutic concentrations.

G-CSF mediated neutrophil augmentation in a unique case of comorbid idiopathic Parkinson's disease and treatment-resistant schizophrenia on clozapine

Treatment of psychosis in Parkinson's disease (PD) is challenging; pharmacological options are limited, with clozapine considered most effective. The risk of agranulocytosis restricts the use of clozapine, but, where this occurs, cautious re-challenge with granulocyte stimulating factor can be successful. We present a unique case of a patient who developed early-onset PD on a background of antecedent treatment-resistant schizophrenia, who had been treated effectively with clozapine for over 15 years with no adverse events. However, during a hospital admission intended to optimise her Parkinsonian medications, she developed persistent neutropenia necessitating clozapine discontinuation. Numerous attempts to re-challenge with clozapine failed until augmentation with lithium and G-CSF was trialled. Two doses of G-CSF led to a sustained increase in the neutrophil count, allowing the continuation of clozapine therapy in the 1 year of follow up. This illustrates the potential for G-CSF to be used to facilitate clozapine use in a patient population not described previously. Neutrophil augmentation allowed the sustained continuation of this effective therapy, treating her psychotic symptoms without detriment to her movement disorder. We suggest that G-CSF might be considered as a treatment option in other cases where clozapine-associated neutropenia obstructs its use.