Clozapine rechallenge following neutropenia using granulocyte colony-stimulating factor: A Quebec case series

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 rechallenge or continuation despite neutropenia or agranulocytosis using colony-stimulating factor: A systematic review

OBJECTIVES

Rechallenge/continuation of clozapine in association with colony-stimulating factors (CSFs) following neutropenia/agranulocytosis has been reported, but many questions remain unanswered about efficacy and safety. This systematic review aims to assess the efficacy and safety of rechallenging/continuing clozapine in patients following neutropenia/agranulocytosis using CSFs.

METHODS

MEDLINE, Embase, PsycInfo, and Web of Science databases were searched from inception date to July 31, 2022. Articles screening and data extraction were realized independently by two reviewers, according to Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) 2020 systematic review guidance. Included articles had to report on at least one case where clozapine was rechallenged/continued using CSFs despite previous neutropenia/agranulocytosis.

RESULTS

Eight hundred forty articles were retrieved; 34 articles met the inclusion criteria, totaling 59 individual cases. Clozapine was successfully rechallenged/continued in 76% of patients for an average follow-up period of 1.9 years. There was a trend toward better efficacy reported in case reports/series, compared with consecutive case series (overall success rates of 84% and 60%, respectively, p-value = 0.065). Two administration strategies were identified, "as-needed" and prophylactic, both yielding similar success rates (81% and 80%, respectively). Only mild and transient adverse events were documented.

CONCLUSIONS

Although limited by the relatively small number of published cases, factors such as time of onset to first neutropenia and severity of the episode did not seem to impact the outcome of a subsequent clozapine rechallenge using CSFs. While the efficacy of this strategy remains to be further adequately evaluated in more rigorous study designs, its long-term innocuity warrants considering its use more proactively in the management of clozapine hematological adverse events as to maintain this treatment for as many individuals as possible.

Combination of strategies to initiate clozapine for refractory schizophrenia in a patient with low neutrophil levels

Clozapine is the only drug with confirmed efficacy for refractory schizophrenia; however, its use is restricted due to the risk of potentially life-threatening side effects, such as agranulocytosis. Although this restriction ensures safety against haematological risks, some patients with refractory schizophrenia who have low neutrophil levels may miss the opportunity to receive clozapine treatment. We herein report the case of a patient with refractory schizophrenia and low neutrophil levels who was successfully initiated on clozapine treatment after the use of several methods for increasing neutrophil levels. These strategies consisted of discontinuation of antipsychotics, treatment with lithium carbonate and adenine, and light exercise before blood testing. Combining these procedures may be an effective option in the treatment of patients with refractory schizophrenia whose neutrophil levels are not sufficient to initiate clozapine.

Clozapine Rechallenge or Continuation Despite Neutropenia, an Extended Follow-up of a Consecutive Quebec Case Series

BACKGROUND

Clozapine is the most efficacious antipsychotic for treatment-resistant schizophrenia. However, clozapine-induced neutropenia may warrant treatment discontinuation, hindering recovery. Several case reports describe clozapine rechallenge or continuation despite neutropenia, although many are subject to selective reporting, with incomplete information and short follow-up periods. Thus, consecutive case series, devoid of such bias, with long-term comprehensive follow-up are needed to better assess this practice. This study aimed to describe consecutively the evolution of every patient in the Québec City catchment area for whom clozapine was either reintroduced after neutropenia during a previous clozapine trial or was maintained despite a first neutropenia.

METHODS

Patients were identified through clozapine's national hematological monitoring database and their medical records between January 1, 2000, and October 22, 2017.

RESULTS

Twenty-three patients were identified, 8 continued clozapine despite neutropenia, while 15 discontinued clozapine and attempted rechallenge; among the latter, 4 patients were successfully rechallenged after agranulocytosis without the use of granulocyte colony-stimulating factors, which is the largest published consecutively. A total of 6 patients experienced further neutropenia episodes. Every patient who had a neutropenia recurrence also had a possible explanation for neutropenia other than exposure to clozapine. After a median follow-up of 4.8 years, 16 patients were still on clozapine and 3 cases discontinued because of a hematological event.

CONCLUSIONS

This study adds further data on the subject of clozapine rechallenge or continuation despite neutropenia. Clozapine rechallenge after agranulocytosis may be less perilous than first thought, but a systematic review on this specific subject is needed.

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.