Incidence and risk for neutropenia/agranulocytosis among clozapine users: A retrospective cohort study

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.

Optimizing co-prescription of clozapine and antiseizure medications: a systematic review and expert recommendations for clinical practice

INTRODUCTION

Antiseizure medication (ASM) add-on to clozapine may be efficient to target clozapine-resistant mood or psychotic symptoms or clozapine-related adverse drug reactions (ADR) such as seizures. We aimed to synthesize the information relevant for clinical practice on the risks and benefits of clozapine-ASM co-prescription.

AREAS COVERED

Articles were identified with MEDLINE, Web of Sciences and PsycINFO search from inception through October 2023. The review was restricted to ASM with mood-stabilizing properties or with potential efficacy for resistant psychotic symptoms (valproate (VPA), lamotrigine, topiramate, carbamazepine, oxcarbazepine).

EXPERT OPINION

VPA add-on to clozapine is associated with a high risk of serious ADR (myocarditis, neutropenia, pneumonia) mostly explained by complex time-dependent drug-drug interactions. The initial inhibitory effects on clozapine metabolism require slow titration to avoid immuno-allergic reactions. After the titration period, VPA has mainly inductive effects on clozapine metabolism that are more marked in smokers requiring therapeutic drug monitoring. Lamotrigine and topiramate add-on may be recommended as the first-line treatment for clozapine-related seizures, but there is limited evidence regarding the efficacy of this strategy for clozapine-resistant psychotic symptoms. Carbamazepine should not be co-prescribed with clozapine because of its potential for agranulocytosis and for inducing clozapine metabolism.

Clozapine-induced agranulocytosis and leukopenia: Incidence, associated factors, and rate of hematologic adverse-effects monitoring in psychiatric out-patient services in Thailand

The present study aimed to investigate the incidence of agranulocytosis and leukopenia and its associated factors in Thai schizophrenia patients treated with clozapine and the rate of hematologic adverse events monitored in clinical practice. Data were collected from the medical records of 641 outpatients at two hospitals. The results showed no cases of agranulocytosis and 20 cases of leukopenia (3.1%), 85% of which were observed after 1 year of prescription. The associated factors were female (p = 0.019) and duration of clozapine prescription (p = 0.026). According to the guideline for safety monitoring, 23.6% of cases had neutrophils count monitoring.

Sodium valproate and clozapine induced neutropenia: A case control study using register data

BACKGROUND

The use of clozapine is limited due to the occurrence of neutropenia, and the rare but life threatening adverse event of agranulocytosis. There is little epidemiological research into clinical factors that may impact on this risk. We conducted a case control study examining the clinical risk factors for neutropenia patients treated with clozapine.

METHOD

A case-control study was conducted within a database of anonymised electronic clinical records. All patients who discontinued clozapine due to a neutropenic event were included as cases. Matched controls were selected from patients with a documented clozapine exposure at the time of the clozapine neutropenic event of the case patient, matched by duration of clozapine treatment.

RESULTS

136 cases and 136 controls were included. In multivariable analysis, the concurrent use of sodium valproate was associated with neutropenia (Odds Raito (OR) 2.28, 95%CI: 1.27-4.11, p=0.006). There was a dose-response effect, with greater associations for higher doses. Patients who discontinued clozapine due to neutropenia were more likely to be of black ethnicity (OR 2.99, p<0.001), were younger (t=5.86, df=267, p<0.001), and received lower doses of clozapine (t=-2.587, p=0.01) than those who did not develop neutropenia.

CONCLUSION

We identified an association between the concurrent use of sodium valproate and an increased risk of clozapine associated neutropenia. These results, taken in combination with the results from previous case series, suggest that the risk of clozapine associated neutropenia could be reduced by avoiding concurrent valproate treatment.

Safety of antipsychotics for the treatment of schizophrenia: a focus on the adverse effects of clozapine

Clozapine, a dibenzodiazepine developed in 1961, is a multireceptorial atypical antipsychotic approved for the treatment of resistant schizophrenia. Since its introduction, it has remained the drug of choice in treatment-resistant schizophrenia, despite a wide range of adverse effects, as it is a very effective drug in everyday clinical practice. However, clozapine is not considered as a top-of-the-line treatment because it may often be difficult for some patients to tolerate as some adverse effects can be particularly bothersome (i.e. sedation, weight gain, sialorrhea etc.) and it has some other potentially dangerous and life-threatening side effects (i.e. myocarditis, seizures, agranulocytosis or granulocytopenia, gastrointestinal hypomotility etc.). As poor treatment adherence in patients with resistant schizophrenia may increase the risk of a psychotic relapse, which may further lead to impaired social and cognitive functioning, psychiatric hospitalizations and increased treatment costs, clozapine adverse effects are a common reason for discontinuing this medication. Therefore, every effort should be made to monitor and minimize these adverse effects in order to improve their early detection and management. The aim of this paper is to briefly summarize and provide an update on major clozapine adverse effects, especially focusing on those that are severe and potentially life threatening, even if most of the latter are relatively uncommon.

Maximizing clozapine utilization while minimizing blood dyscrasias: evaluation of patient demographics and severity of events

The aim of this study was to determine whether patient characteristics such as age, sex, race/ethnicity, and frequency of monitoring play a role in clozapine-related blood dyscrasias. This study examined all neutropenic events to identify any potential demographic qualities that may pose increased risk to individuals receiving clozapine treatment in accordance with the FDA guidelines released in 2005. These guidelines required the addition of absolute neutrophil count (ANC) tests in addition to white blood cell (WBC) counts to regular monitoring and a reduction in the frequency of testing to once monthly after 1 year of satisfactory WBC counts and ANCs. The previous schedule neither included ANC testing nor allowed for further reductions in the frequency of testing after 1 year, with patients continuing to be tested every 2 weeks indefinitely. This is a retrospective, closed chart review of all patients who received clozapine at the State Psychiatric Center and experienced a leukopenic/neutropenic event and/or who had a substantial drop in WBC/ANC from January 2009 to December 2011. A subset of patients who were identified as achieving 'non-rechallengeable' status with either an ANC and/or WBC threshold value from 2001 to 2014 were also examined. This protocol was approved by the New York State Psychiatric Institute Institutional Review Board. A total of 193 patients were included in the study. Males experienced more total events at 6.4 events per person compared with 5.2 events per woman. White patients had 6.5 total events per person compared with 4.2 total events per Black patient; however, Black patients experienced more moderate leukopenia/granulocytopenia events compared with Whites. Regardless of race or ethnicity, patients in the 40-49-year age range had the most events at 8.1 events per person and also presented with the highest number of moderate leukopenia/granulocytopenia events as did those scheduled for weekly monitoring. Conversely, the majority of patients with no recorded events were female and either 20-29 or 60-69 years of age. In total, 16 patients were exclusively designated as non-rechallengeable from 2001 to 2014 and only had one single blood event prompting this clozapine monitoring status. Of these 16 patient events, seven were White males, eight were White females, and one was a Black female with roughly 40% of those patients in the 50-59-year age group. Currently published predictions on possible demographic risk groups may not reflect clinical experience and may pose unnecessary treatment barriers in the provision of clozapine. Although the healthcare team should be aware of the possible demographic predictors of blood dyscrasias when using clozapine, treatment goals and monitoring strategies must be individualized to ensure successful clozapine therapy.