Escaping the Long Shadow Cast by Agranulocytosis: Reflections on Clozapine Pharmacovigilance Focused on the United Kingdom

Clozapine pharmacovigilance in Croatia: Underreporting of specific adverse drug reactions and excellent reporting of suicide attempts

Croatia has implemented anti-suicide measures due to its high suicide rates. Clozapine has anti-suicidal effects. Using the international database (VigiBase), we explored Croatia's unusual clozapine pharmacovigilance. First, we compared the United Kingdom (UK) with Croatia for clozapine adverse drug reactions (ADRs) and fatal outcomes from clozapine's introduction through January 15, 2023. If the UK is considered 1, and after adjusting for population, Croatia had much lower rates (1 vs. 0.08 for clozapine ADR reports, 1 vs. 0.02 for fatal outcomes and 1 vs. 0.14 for percentage of clozapine reports out of all drug reports). Through 2023, the UK had 52,252 ADR reports and 6,567 fatal outcomes from clozapine-treated patients vs. Croatia with 395 reports and 6 fatal outcomes. The Croatian pharmacovigilance agency (and most national agencies) needs to learn from the UK's agency to better report clozapine ADRs. Second, we analyze suicide behaviors in Croatian clozapine-treated patients reported to VigiBase. Through 2023 the UK reported 537 clozapine-treated patients with at least 1 suicidal behavior versus 95 from Croatia. After adjusting for population, the UK reported a much smaller number of reports of suicidal behavior than Croatia (1 vs. 2.73). This overreporting by Croatian physicians may be a sign of the success of Croatia's anti-suicide measures. The percentage of fatal outcomes in 77 Croatian patients with an intentional overdose was 1.3 % (1/77) vs. 16.8 % in 411 non-Croatian patients, but this is possibly contaminated by early reporting (patients might die after the report). Longitudinal studies of clozapine overdoses in Croatia are needed.

Therapeutic Reference Range for Clozapine Plasma Levels in Parkinson's Disease or Dementia: A Systematic Review and Individual Participant Data Meta-analysis

Clozapine is a recommended treatment for psychotic symptoms in patients with Parkinson's disease (PD) and/or dementia. However, the therapeutic reference range for clozapine in these patients has not been established hitherto.The study was performed in three university hospitals in Germany and Switzerland, including clozapine-treated patients with PD and/or dementia. The primary outcome was tolerability based on reports of adverse drug reactions and/or changes in laboratory tests or electrocardiogram and/or clozapine discontinuation. We meta-analyzed demographic and pharmacokinetic parameters in patients tolerating clozapine well versus not. A meta-analytic summary receiver operating characteristic (SROC) to establish the clozapine upper level associated with poor tolerability was estimated.We analyzed a total of 99 patients suffering from PD (56.6%) and/or dementia (49.5%) with a mean age of 70.3±9.5 years and 41.4% females; poor tolerability was reported in 26 of 99 patients (26.3%). When comparing patients with and without poor tolerability, there were no differences in age, body mass index, sex, smoking, or clozapine dose, nor did we find statistically significant differences in clozapine levels (standardized mean difference 0.46, 95% confidence interval - 0.04 to 0.96, p=0.07), and heterogeneity was low (I2=0.0%). Clozapine blood levels above 193 ng/mL were associated with poor tolerability (SROC area-under-curve 0.6, sensitivity 39.7%, specificity 79.9%).One of four patients with PD and/or dementia treated with clozapine did not tolerate clozapine well, which was associated with a trend toward elevated clozapine concentrations. Monitoring drug levels may help to improve tolerability in these patients.

Letter to the FDA Proposing Major Changes in the US Clozapine Package Insert Supported by Clozapine Experts Worldwide. Part II: A Review of Fatal Outcomes in US Pharmacovigilance Data and Proposed Changes

PURPOSE/BACKGROUND

This is the second part of a 2-part article that proposes improving the United States (US) clozapine package insert. Part II focuses on fatal outcomes and the 5 boxed warnings, 4 specifically for clozapine: severe neutropenia, seizure, orthostatic hypotension and myocarditis, and 1 for all antipsychotics (elderly with dementia).

METHODS

US reports to the World Health Organization's global pharmacovigilance database were analyzed from clozapine's introduction to January 15, 2023.

FINDINGS/RESULTS

The US was the top reporter worldwide for clozapine with 56,003 reports and 9587 associated fatal outcomes. The 4 clozapine boxed warnings were associated with 534 fatal outcomes (218 with severe neutropenia, 131 with seizures, 125 with orthostasis, 36 with myocarditis, 24 with cardiomyopathy, and 0 with mitral valve prolapse). With no boxed warnings, pneumonia was associated with 674 fatal outcomes and increased white blood cell count (a sign of infection) with 596 fatal outcomes. After considering overlaps, pneumonia and increases in white blood cell count explained 900 fatalities, or 9.4% of 9587 fatal outcomes. The Food and Drug Administration continues to focus on severe neutropenia which was associated with only 218 or 2.3% of fatal outcomes, whereas 97.7% of fatal outcomes reported in US clozapine-treated patients had another cause.

IMPLICATIONS/CONCLUSIONS

To help prevent future deaths in clozapine-treated patients, the clozapine package insert should focus on fatal outcomes during infections. Part II offers detailed solutions regarding current boxed warnings and lack of a warning for pneumonia and other infections. The Supplementary Material includes letters of support from 124 non-US clozapine experts from 44 countries/regions who support Parts I and II.

Clozapine may consistently protect from suicidal behaviors while other antipsychotics may lack a specific protective effect: a comprehensive VigiBase study interpreted in the context of the prior literature

BACKGROUND

In the United States, clozapine was first approved for treatment-resistant schizophrenia and then for suicidality in schizophrenia psychoses. Systematic reviews support clozapine's anti-suicidal effect, but the forensic literature stresses its lethality during overdoses.

RESEARCH DESIGN AND METHODS

Clozapine reports to the international pharmacovigilance database (VigiBase) were analyzed for suicidal ideation, suicide attempts, intentional overdose, and completed suicides from introduction to 1 January 2024. VigiBase uses the information component (IC) as a disproportionality analysis.

RESULTS

The clozapine ICs (range: other antipsychotics) were: 1) suicidal ideation IC = 0.570 with IC025 = 0.454 to IC975 = 0.680 (IC = 3.568 for aripiprazole and 1.729 for risperidone), 2) suicide attempt IC = 1.428 with IC025 = 1.323 to IC975 = 1.529 (IC = 4.150 for quetiapine and 2.968 for risperidone), 3) intentional overdose: IC = 0.995 with IC025 = 0.864 to IC975 = 1.120 (IC = 4.080 for quetiapine and 1.957 for aripiprazole), and 4) completed suicide IC = 1.133 with IC025 = 1.026 to IC975 = 1.235 (IC = 4.648 for quetiapine and 2.160 for risperidone). In summary, all clozapine ICs were significantly lower. We found 2391 clozapine-treated patients on the suicidality spectrum (627 cases with suicidal ideation, 752 with suicide attempt, 488 with intentional overdose, and 731 with completed suicide) but many were taking other antipsychotics. The most frequent reporting countries were the United States, the United Kingdom, and Croatia.

CONCLUSION

This pharmacovigilance study, with all its inherent limitations, provides independent proof, not overlapping with prior literature, that clozapine may have specific strong anti-suicidal effects that do not appear to be present in other antipsychotics. Further VigiBase studies are needed to compare the lethality of an intentional overdose of clozapine (14.3%) with other antipsychotics.

Investigating in VigiBase over 6000 cases of pneumonia in clozapine-treated patients in the context of the literature: focus on high lethality and the association with aspiration pneumonia

BACKGROUND

The literature associates clozapine with pneumonia/aspiration pneumonia.

RESEARCH DESIGN AND METHODS

The international pharmacovigilance database (VigiBase™) uses the information component (IC) as statistical signal. VigiBase clozapine reports were analyzed for pneumonia/aspiration pneumonia from introduction to 10 May 2023.

RESULTS

There were 6392 cases of all types of pneumonia (5572 cases of pneumonia, 775 of aspiration pneumonia, and 45 combined). The IC was 3.52 for aspiration pneumonia, introduced as a VigiBase label in 2003, and 1.91 for pneumonia. Patients were reclassified as 3628 with no signs of aspiration and 1533 with signs. Signs of aspiration were strongly associated with some co-medications: olanzapine, odds ratio (OR) = 23.8, 95% confidence interval (CI), 14.9-38.0; risperidone OR = 18.6, CI, 11.4-30.4; valproic acid, OR = 5.5, CI, 4.5-6.6; and benzodiazepines OR = 5.5, CI, 4.5-6.6. In 2415 cases with completed data, fatal outcomes made up 45% (signs of aspiration made no difference), but there was wide variability from 0% (females <45 years of age; duration ≤30 days) to 76% (males >64 years of age; duration >1 year). During the first week, pneumonia was associated with 1) very high titration doses, 2) very small doses in Parkinson's disease, and 3) Japan vs other countries.

CONCLUSIONS

In clozapine-treated patients: 1) at least 30% of pneumonia cases may be aspiration pneumonia, 2) stopping some co-medications may decrease the risk of aspiration pneumonia, 3) average lethality in pneumonia was 45% but may be around 75% in geriatric patients with long-term treatment, and 4) safer titrations may sometimes require 5-mg tablets.

An expert review of clozapine in Latin American countries: Use, monitoring, and pharmacovigilance

There is growing interest in clozapine clinical use, monitoring, and research, particularly adverse drug reactions (ADRs) other than agranulocytosis. In this study we focused on clozapine pharmacovigilance. Hence, we contacted clinicians and researchers in Latin America and requested information about local psychiatric services, clozapine availability, clinical use, and ADR monitoring with the VigiBase system. Only two countries have the minimum recommended number of psychiatric beds (15 per 100,000 residents): Uruguay (N = 34.9) and Argentina (N = 17). Bolivia is the only country where clozapine is unavailable. Nine out of twenty countries (45 %) reported ADRs to VigiBase. Argentina, Brazil, Chile, Colombia, and Mexico published national guidelines for schizophrenia treatment. Chile is the sole country with clozapine clinics with drug serum monitoring. Ethnicity-related drug titration in not described in package inserts in any country. We examined in detail the 9 most frequent and important clozapine ADRs in the worldwide database (pneumonia, sudden death, cardiac arrest, agranulocytosis, myocarditis, constipation, arrhythmia, seizure, and syncope). These 9 ADRs led to 294 reports with fatal outcomes in Argentina (N = 3), Brazil (N = 3), Chile (N = 2), and Peru (N = 1). Agranulocytosis was reported from 7 countries: constipation or seizures from 8 countries. Only two countries reported pneumonia and one country reported myocarditis. The number of clozapine reports in VigiBase has no relationship to the country's population. All Latin American countries underreport clozapine associated ADRs. Latin American governments, along with clinicians, researchers, and educators, should optimize clozapine use and monitoring for the benefit of people with severe mental and some neurological disorders.

Revealing the reporting disparity: VigiBase highlights underreporting of clozapine in other Western European countries compared to the UK

BACKGROUND

Pharmacovigilance studies indicate clozapine history is marked by adverse drug reactions (ADRs).

OBJECTIVE

In a 2021 article, the United Kingdom (UK) had >90 % of European clozapine-related fatal outcomes in VigiBase, the World Health Organization's pharmacovigilance database. Two possibly opposing hypotheses could explain this disparity: 1) fewer reported fatal outcomes in other Western European countries mainly reflect underreporting to VigiBase, and 2) the higher number of UK reports reflects higher real relative mortality.

METHODS

VigiBase reports from clozapine's introduction to December 31, 2022, were studied for ADRs and the top 10 causes of fatal outcomes. The UK was compared with 11 other top reporting Western countries (Germany, Denmark, France, Finland, Ireland, Italy, Netherlands, Norway, Spain, Sweden and Switzerland). Nine countries (except Ireland and Switzerland) were compared after controlling for population and clozapine prescriptions.

RESULTS

The UK accounted for 29 % of worldwide clozapine-related fatal outcomes, Germany 2 % and <1 % in each of the other countries. The nonspecific label "death" was the top cause in the world (46 %) and in the UK (33 %). "Pneumonia" was second in the world (8 %), the UK (12 %), Ireland (8 %) and Finland (14 %). Assuming that our corrections for population and clozapine use are correct, other countries underreported only 1-10 % of the UK clozapine fatal outcome number.

CONCLUSIONS

Different Western European countries consistently underreport to VigiBase compared to the UK, but have different reporting/publishing styles for clozapine-related ADRs/fatal outcomes. Three Scandinavian registries suggest lives are saved as clozapine use increases, but this cannot be studied in pharmacovigilance databases.

A 12-month audit of clozapine associated myocarditis in a South Australian Local Health Network: The importance of screening and personalised titration

Clozapine is effective in up to 50 % of patients resistant to other antipsychotics. Its use is restricted to third-line due to adverse effects which include myocarditis. Australia reports the highest incidence of clozapine-associated myocarditis (CAM) in the context of pharmacovigilance and relatively rapid titration. An audit of patients commenced on clozapine within the Central Adelaide Local Health Network (CALHN) between 2012 and 2015 found an incidence of 8.6 %. We present here a case series from a follow up audit considering titration relevant risk factors for CAM. We reviewed anecdotal cases and data from all hospital-based commencements of clozapine across CALHN for the period July 2021 to June 2022 using pharmacy and medical record databases. We identified 5 cases of CAM and all had risk factors impacting on clozapine metabolism, including rapid titration, elevated baseline CRP, Asian ethnicity and concomitant treatment with inhibitors of clozapine metabolism. While personalisation of clozapine treatment needs further investigation in prospective trials, slower titration to lower targets for risk groups may not impact on hospital length of stay and has the potential to significantly reduce the burden of adverse events. Australian manufacturer approved titration rates exceed those recommended for personalised dosing and may not be safe for patients with risk factors. Early clozapine levels at week two could identify slow metabolisers for dose adjustment. Closer ties between psychiatrists and cardiologists are critical for the development of protocols for safely maintaining clozapine treatment during low level cardiac inflammation and to support safe rechallenge.

Response rates to sequential trials of antipsychotic medications according to algorithms or treatment guidelines in psychotic disorders. A systematic review and meta-analysis

BACKGROUND

There is a relative lack of research evaluating the outcomes when treatment guidelines or algorithms for psychotic disorders are followed. This systematic review and meta-analysis determined the response rates to antipsychotic medications at different stages of these algorithms and whether these response rates differ in first episode cohorts.

METHODS

Data sources: A systematic search strategy was conducted across four databases PubMed, EMBASE, PsycINFO (Ovid) and CINAHL. Studies that had sequential trials of different antipsychotic medications were included. A meta-analysis of proportions was performed using random effects models and sub-group analysis in first episode psychosis studies.

RESULTS

Of the 4078 unique articles screened, fourteen articles, from nine unique studies, were eligible and included 2522 participants. The proportion who experienced a response to any antipsychotic in the first stage of an algorithm was 0.53 (95 % C.I.:0.38,0.68) and this decreased to 0.26 (95 % C.I.:0.15,0.39) in the second stage. When clozapine was used in the third stage, the proportion that achieved a response was 0.43 (95 % C.I. 0.19, 0.69) compared to 0.26 (95 % C.I.:0.05,0.54) if a different antipsychotic was used. Four studies included 907 participants with a first episode of psychosis and the proportions that achieved a response were: 1st stage: 0.63 (95 % C.I.: 0.45, 0.79); 2nd stage: 0.34 (95 % C.I.:0.16,0.55); clozapine 3rd stage: 0.45 (95 % C.I.:0.0,0.97), different antipsychotic 3rd stage: 0.15 (95 % C.I.,0.01,0.37).

DISCUSSION

These findings support the recommendation to have a trial of clozapine after two other antipsychotic medications have been found to be ineffective.

Clozapine safety monitoring and related research in psychiatry and neurology in South America: A scoping review

The quality and quantity of clozapine safety monitoring considerably differs among South American countries and mainly focus on hematological surveillance. Few studies have been conducted on other clozapine-related adverse effects (ADRs) and mainly refer to case reports and literature reviews. We retrieved thirty-nine publications on clozapine related ADRs others than neutropenia. Studies in Brazil and Venezuela accounted for 67 % of all the publications, and 8 out of 12 countries published 2 or less manuscripts. Only Chile offers serum clozapine level measurement in public institutions. Given the recently recognized role of ethnicity, gender, smoking, obesity drug interactions in optimal clozapine administration, modernization of clozapine clinical use and research in psychiatry and neurology most be broadcasted and stimulated in South American countries.

Clozapine and neutrophil response in patients of African descent: A six-month, multinational, prospective, open-label clinical trial

INTRODUCTION

Clozapine is the most effective antipsychotic for treatment-resistant schizophrenia, but it is markedly underutilized, particularly in the US Black population, partly because of concern over clozapine-associated low absolute neutrophil count (ANC). People of African descent have a lower normative ANC range than the White population, which is associated with a specific "ACKR1-null" ("Duffy null") CC genotype (SNP rs2814778) on the ACKR1 gene, termed benign ethnic neutropenia (BEN). The range of ANC variability and safety of clozapine have not been established in people with BEN or examined prospectively in people of African descent.

METHODS

We completed a multisite, 6-month, prospective, open-label clinical trial of clozapine treatment in people of African descent with schizophrenia spectrum disorders for whom clozapine was clinically indicated, with or without the ACKR1-null genotype. We examined clozapine safety and weekly ANC during clozapine treatment and evaluated ANC variability by ACKR1-null genotype, sex, study site, and clozapine dosing using repeated measures analysis of covariance. Genotype was assayed using TaqMan® technology.

RESULTS

We enrolled 274 participants, of whom 227 (82.8 %) completed 6 months of clozapine treatment. There was one case of severe neutropenia (<500 cells/mm3) (0.36 %) over 1467.6 person-months of clozapine exposure. This participant recovered without sequelae after discontinuation of clozapine. Of the 249 participants with known genotypes, 199 (79.9 %) had the ACKR1-null genotype. Neutropenia (<1500 cells/mm3) occurred significantly more often in the ACKR1-null group (33 % [65/199]) than in those with the T allele (6 % (3/50); p < 0.001). Fourteen (5 %) patients discontinued due to adverse events. Rates of infection and fever were low and sialorrhea was the commonest side effect (N = 187, 68 %).

CONCLUSION

To our knowledge, this is the largest prospective clozapine trial in people of African descent. Severe neutropenia was rare, despite the high prevalence (80 %) of the ACKR1-null genotype. Our findings suggest that clozapine can be used safely in Black patients including those with BEN.

Evaluation of major adverse events of clozapine based on accordance to an international titration guideline

Introduction

Clozapine is the only antipsychotic approved for treatment-resistant schizophrenia, but without appropriate monitoring, it can be associated with potentially fatal outcomes. An International Adult Clozapine Titration Guideline categorizes patients into normal or slow metabolizers. Categorization provides clozapine titration schedules and recommends regular c-reactive protein (CRP) and clozapine concentration monitoring to reduce the risk of adverse drug reactions (ADRs). The impact of the guideline on clozapine ADRs has not been evaluated.

Methods

A retrospective chart review assessed clozapine titrations, laboratory monitoring, ADRs, and discontinuations for clozapine-naive adult inpatients at a single center from January 1, 2013, to June 1, 2022. Each patient's cumulative weekly clozapine dosage was compared with their guideline recommended dosage to create a percent accordance. Linear logistic regression evaluated the relationship between titration speed and the presence of an ADR, while descriptive statistics analyzed laboratory monitoring.

Results

Forty-three patients were included, with the majority being White males with schizophrenia. An inverse relationship existed between the last inpatient week clozapine dose percent accordance and the probability of an ADR. Nonobese patients were less likely than obese patients to experience an ADR (odds ratio = 0.17; 95% CI, 0.03-0.99). CRP and clozapine concentration monitoring was suboptimal.

Discussion

Based on our small retrospective review of primarily White males, more aggressive clozapine titrations did not increase ADRs. Future studies with more diverse samples are needed and should focus on specific ADRs, which may have increased occurrence with rapid titrations. Obese patients were at higher risk of ADRs, correlating with the guideline-recommended slower titrations for these patients.

Adverse drug reactions and their fatal outcomes in clozapine patients in VigiBase: Comparing the top four reporting countries (US, UK, Canada and Australia)

BACKGROUND

Pharmacovigilance findings and box warnings in the clozapine package inserts have marked the history of clozapine.

OBJECTIVE

This is the largest review of clozapine adverse drug reactions (ADRs) and their associated fatal outcomes. Reports to the World Health Organization's global pharmacovigilance database, VigiBase™, were analyzed, extending from clozapine's introduction to December 31, 2022.

METHODS

The analysis focused on the top four reporting countries: United States (US), United Kingdom (UK), Canada and Australia (83 % of fatal outcomes worldwide). Attempts were made to control for population and clozapine prescription in each country.

RESULTS

Clozapine ADRs worldwide accounted for 191,557 reports, with the highest number (53,505) in "blood and lymphatic system disorder". Of the 22,596 fatal outcomes reported in clozapine patients, 9587 were from the US, 6567 from the UK, 3623 from Canada and 1484 from Australia. The top category worldwide in fatal outcomes was nonspecifically labeled "death" with 46 % (range 22-62 %). "Pneumonia" was second with 30 % (range 17-45 %). Agranulocytosis was numerically only the 35th top clozapine ADR associated with fatal outcomes. On average, 2.3 clozapine ADRs were reported per fatal outcome. Infections were associated with 24.2 % of the UK fatal outcomes (9.4 %-11.9 % in the 3 other countries).

CONCLUSIONS

The four countries appeared to report clozapine ADRs in different ways, making comparisons difficult. We estimated higher fatal outcomes in the UK and Canada after controlling for cross-sectional estimations of population and published clozapine use. This last hypothesis is limited by the lack of precise estimation of accumulated clozapine use in each country.

A scoping review of literature on clozapine from former USSR states published in Russian language

OBJECTIVE

Access to literature on clozapine in Russian language remains strikingly limited. We aimed to identify and translate clinical evidence on clozapine-based treatment outcomes.

METHODS

We performed a systematic review in PubMed, Embase and scientific indexes from former USSR states searching for articles published in Russian from the database inception till January 2023 and summarized the data in a scoping review (PROSPERO Reg. Number CRD42023386737).

RESULTS

A total of 60 papers were included comprising eight main topic categories: 1) clozapine-related intoxications (n = 20), 2) effectiveness/efficacy and safety of clozapine treatment (n = 14), 3) adverse drug-induced reactions (ADRs) related to clozapine treatment (n = 9), 4) therapeutic drug monitoring for clozapine (n = 5), 5) combination of clozapine and non-pharmacological treatments (n = 4), 6) pharmacoepidemiology of clozapine (n = 3), 7) effects of clozapine on the brain electrical activity (n = 3), and 8) novel clozapine formulations (n = 2). Among clozapine-related intoxications there were reports of criminal poisoning, which was associated with low lethality. Worse outcomes were accompanied by systemic reactions to intoxications. Clinical benefits of hemoadsorption were reported in the management of clozapine-related intoxications. Only half of studies reporting clozapine effectiveness used standardized scales to assess outcomes. Clozapine superiority in treatment-resistant schizophrenia (TRS) was replicated in one trial. No reports of clozapine-related agranulocytosis were identified. Clozapine ranked among most prescribed antipsychotics for TRS and non-TRS.

CONCLUSIONS

As clinical research in former USSR states is advancing to adopt western clinical research standards, comparability and extrapolation of findings is expected to increase, with transfer of older findings to clinical practice being particularly challenging.

An expert review of clozapine in Eastern European countries: Use, regulations and pharmacovigilance

OBJECTIVES

To compare the prevalence, regulations, and pharmacovigilance practices of clozapine use in Eastern European countries (except Russia).

METHODS

Questionnaires and data from administrative databases (2016 and 2021), package inserts and national guidelines were collected from 21 co-authors from 21 countries. Reports of clozapine adverse drug reactions (ADRs) sent to the global pharmacovigilance database (VigiBase™) were analyzed from introduction to December 31, 2022.

RESULTS

Clozapine prescription among antipsychotics in 2021 varied six-fold across countries, from 2.8 % in the Czech Republic to 15.8 % in Montenegro. The utilization of antipsychotics in both 2016 and 2021 was highest in Croatia, and lowest in Serbia in 2016, and Montenegro in 2021, which had half the defined daily dose (DDD)/1000/day compared to the Croatian data. From 2016 to 2021, the prevalence of antipsychotic use increased in almost all countries; the proportion of clozapine use mainly remained unchanged. Differences were detected in hematological monitoring requirements and clozapine approved indications. Only a few national schizophrenia guidelines mention clozapine-induced myocarditis or individual titration schemes. The VigiBase search indicated major underreporting regarding clozapine and its fatal outcomes. By comparison, the United Kingdom had less than half the population of these Eastern European countries but reported to VigiBase more clozapine ADRs by 89-fold and clozapine fatal outcomes by almost 300-fold.

CONCLUSION

Clozapine is under-utilized in Eastern European countries. Introducing individualized clozapine treatment schedules may help to maximize clozapine benefits and safety. Major improvement is needed in reporting clozapine ADRs and fatal outcomes in Eastern European countries.

Can Slow Personalized Titration Using C-Reactive Protein Monitoring Decrease the High Rates and Mortality of Clozapine-Associated Myocarditis Seen in Some Countries? A Call for Research

PURPOSE/BACKGROUND

The hypothesis that slower personalized titration may prevent clozapine-associated myocarditis and decrease the disproportion incidence of 3% found in Australia was not described in a recent Australian article in this journal.

METHODS

Six countries in addition to Australia have published information suggesting a similar incidence of clozapine-associated myocarditis. On September 19, 2023, PubMed searches were updated for articles from the United States, Korea, Japan, Canada, New Zealand, and Turkey.

FINDINGS/RESULTS

An incidence of 3.5% (4/76) was found in a US hospital, but US experts were the first to propose that clozapine-associated myocarditis may be a hypersensitivity reaction associated with rapid titration and possibly preventable. Koreans and Japanese are of Asian ancestry and need lower minimum therapeutic doses for clozapine than patients of European ancestry. A 0.1% (2/1408) incidence of myocarditis during clozapine titration was found in a Korean hospital, but pneumonia incidence was 3.7% (52/1408). In 7 Japanese hospitals, 34% (37/110) of cases of clozapine-associated inflammation were found during faster titrations (based on the official Japanese titration) versus 13% (17/131) during slower titrations (based on the international titration guideline for average Asian patients). Recent limited studies from Canada, New Zealand, and Turkey suggest that slower personalized titration considering ancestry may help prevent clozapine-associated myocarditis.

IMPLICATIONS/CONCLUSIONS

Other countries have very limited published data on clozapine-associated myocarditis. Based on a recent Australian case series and these non-Australian studies, the author proposes that Australia (and other countries) should use slow personalized titration for clozapine based on ancestry and c-reactive protein monitoring.