Clozapine-associated myocarditis in the World Health Organization's pharmacovigilance database: Focus on reports from various countries

Acute exposure to clozapine and sodium valproate impairs oxidative phosphorylation in human cardiac mitochondria

The only antipsychotic that is approved and recommended for the treatment of otherwise treatment-resistant schizophrenia is clozapine (CLZ). Unfortunately, CLZ can cause serious cardiotoxicities such as myocarditis and cardiomyopathy. The co-administration of sodium valproate (VPA) during initiation is a well-established risk factor for the development of CLZ-induced myocarditis. However, the mechanisms behind these cardiac adverse effects and the role of VPA co-administration are not understood. Preliminary evidence for the development of cardiac mitochondrial dysfunction has previously been reported in both rodent models and immortalised cell lines. This investigation aimed to determine the functional effects of CLZ and VPA on human cardiac mitochondria to improve the current understanding of how cardiotoxicity develops. Small samples of human atrial tissue from consenting patients undergoing a coronary artery bypass grafting procedure were freshly collected and utilised to investigate the acute effects of each drug on mitochondrial O2 consumption using high-resolution respirometry. Both drugs significantly decreased mitochondrial O2 consumption by a magnitude of 32 % following CLZ exposure, 25 % following VPA exposure, and 25 % following combined CLZ+VPA exposure during complex I- and II-linked oxidative phosphorylation. These results demonstrate acute bioenergetic dysfunction with exposure to both drugs, alone and in combination. We propose that cardiac mitochondria become a key focus in future research seeking to improve the risk-predictive, diagnostic, and treatment guidelines surrounding CLZ-induced cardiotoxicity.

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.

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.

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.

Clozapine-associated pericarditis and pancreatitis in children and adolescents: A systematic literature review and pharmacovigilance study using the VigiBase database

BACKGROUND

The literature has paid very little attention to pericarditis, pericardial effusion and pancreatitis during clozapine treatment in children and adolescents.

METHODS

Cases of clozapine-associated pericarditis and pancreatitis in children were studied using searches in: 1) PubMed (June 16, 2023), and 2) the World Health Organization's pharmacovigilance database (June 1, 2022), VigiBase. VigiBase uses a logarithmic measure of disproportionality called the information component (IC).

RESULTS

The PubMed search yielded 3 clozapine-associated pericarditis cases, 1 pancreatitis case and 1 with both. VigiBase provided a significant clozapine-associated pericarditis IC = 3.6 with an IC025 = 2.9 (only 3 cases were expected while 22 were observed). VigiBase provided a significant clozapine-associated pancreatitis IC = 2.2 with an IC025 = 1.4 (only 3 cases were expected while 16 were observed). In VigiBase clozapine-associated pericarditis and pericardial effusion in youth looked similar and on a continuum with myocarditis, as myocarditis, pericarditis and pancreatitis appeared to occur mainly during clozapine titration. Combining PubMed and VigiBase we identified: 1) 29 cases of at least possible clozapine-associated pericarditis/pericardial effusion (6 probable and 23 possible) including 7 cases with and 22 without myocarditis, and 2) 17 cases of clozapine-associated pancreatitis (1 definite and 16 possible). Two of the pancreatitis cases occurred during overdoses. No fatal outcomes were found in any clozapine-associated pericarditis and pancreatitis cases.

CONCLUSIONS

Despite the lack of attention in the literature to clozapine-associated pericarditis and pancreatitis, results demonstrate that they can happen in youth, particularly during titration. Pericarditis and pancreatitis appear to be forms of clozapine-associated inflammation during dose titration.

Association between initial clozapine titration and pneumonia risk among patients with schizophrenia in a Korean tertiary hospital

Pneumonia is a significant adverse drug reaction (ADR) associated with clozapine, characterized by high mortality and potential linkage with other inflammatory responses. Despite the critical nature, research regarding the development of pneumonia during initial clozapine titration remains limited. This retrospective study included 1408 Korean inpatients with schizophrenia spectrum disorders. Data were collected from January 2000 to January 2023. Pneumonia developed in 3.5 % of patients within 8 weeks of clozapine initiation. Patients who developed pneumonia were taking a greater number and higher dose of antipsychotics at baseline (2.14 vs. 1.58, p < 0.001; 25.64 vs. 19.34, p = 0.012). The average onset occurred 17.24 days after initiation, on an average dose of 151.28 mg/day. Titration was either paused or slowed in most of these patients, with no reported fatalities. The types of pneumonia included aspiration pneumonia, mycoplasma pneumonia, bronchopneumonia, and COVID-19 pneumonia. Myocarditis, drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome, and urinary tract infections were also identified. Logistic regression analysis revealed that a greater number of concomitant antipsychotics (odds ratio [OR] = 1.59, p = 0.027) and concomitant benzodiazepine use (OR = 2.33, p = 0.005) at baseline were associated with an increased risk of pneumonia. Overall, pneumonia development during clozapine titration is linked with other inflammatory ADRs, suggesting a shared immunological mechanism. Close monitoring is recommended, especially for patients taking multiple antipsychotics and benzodiazepines. Further studies involving repeated measures of clozapine concentrations at trough and steady state, along with a more detailed description of pneumonia types, are warranted.

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.

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.

Promoting safer and wider worldwide use of clozapine

This issue focuses on the past, the present and the future of clozapine. Of the 43 clozapine articles, nine are historical articles dealing with the past, 29 deal with the present and five with laboratory assays which may influence its future use. These 43 articles include 219 different authors from 56 countries/regions and five continents.

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.

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.

Navigating duplication in pharmacovigilance databases: a scoping review

OBJECTIVES

Pharmacovigilance databases play a critical role in monitoring drug safety. The duplication of reports in pharmacovigilance databases, however, undermines their data integrity. This scoping review sought to provide a comprehensive understanding of duplication in pharmacovigilance databases worldwide.

DESIGN

A scoping review.

DATA SOURCES

Reviewers comprehensively searched the literature in PubMed, Web of Science, Wiley Online Library, EBSCOhost, Google Scholar and other relevant websites.

ELIGIBILITY CRITERIA

Peer-reviewed publications and grey literature, without language restriction, describing duplication and/or methods relevant to duplication in pharmacovigilance databases from inception to 1 September 2023.

DATA EXTRACTION AND SYNTHESIS

We used the Joanna Briggs Institute guidelines for scoping reviews and conformed with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Extension for Scoping Reviews. Two reviewers independently screened titles, abstracts and full texts. One reviewer extracted the data and performed descriptive analysis, which the second reviewer assessed. Disagreements were resolved by discussion and consensus or in consultation with a third reviewer.

RESULTS

We screened 22 745 unique titles and 156 were eligible for full-text review. Of the 156 titles, 58 (47 peer-reviewed; 11 grey literature) fulfilled the inclusion criteria for the scoping review. Included titles addressed the extent (5 papers), prevention strategies (15 papers), causes (32 papers), detection methods (25 papers), management strategies (24 papers) and implications (14 papers) of duplication in pharmacovigilance databases. The papers overlapped, discussing more than one field. Advances in artificial intelligence, particularly natural language processing, hold promise in enhancing the efficiency and precision of deduplication of large and complex pharmacovigilance databases.

CONCLUSION

Duplication in pharmacovigilance databases compromises risk assessment and decision-making, potentially threatening patient safety. Therefore, efficient duplicate prevention, detection and management are essential for more reliable pharmacovigilance data. To minimise duplication, consistent use of worldwide unique identifiers as the key case identifiers is recommended alongside recent advances in artificial intelligence.

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

PURPOSE/BACKGROUND

A recent article in this journal presented a US perspective regarding the modernization of clozapine prescription and proposed an escape from the long shadow cast by agranulocytosis.

METHODS

Here, an international group of collaborators discusses a point of view complementary to the US view by focusing on worldwide outcomes of clozapine usage that may be uneven in terms of frequency of clozapine adverse drug reactions.

FINDINGS/RESULTS

Studies from the Scandinavian national registries (Finland and Denmark) did not find increased mortality in clozapine patients or any clear evidence of the alleged toxicity of clozapine. Data on clozapine-associated fatal outcomes were obtained from 2 recently published pharmacovigilance studies and from the UK pharmacovigilance database. A pharmacovigilance study focused on physician reports to assess worldwide lethality of drugs from 2010 to 2019 found 968 clozapine-associated fatal outcomes in the United Kingdom. Moreover, the United Kingdom accounted for 55% (968 of 1761) of worldwide and 90% (968 of 1073) of European fatal clozapine-associated outcomes. In a pharmacovigilance study from the UK database (from 2008 to 2017), clozapine was associated with 383 fatal outcomes/year including all reports from physicians and nonphysicians. From 2018 to 2021, UK clozapine-associated fatal outcomes increased to 440/year.

IMPLICATIONS/CONCLUSIONS

The interpretation of fatal outcomes in each country using pharmacovigilance databases is limited and only allows gross comparisons; even with those limitations, the UK data seem concerning. Pneumonia and myocarditis may be more important than agranulocytosis in explaining the uneven distribution of fatal outcomes in clozapine patients across countries.

Respiratory aspiration during treatment with clozapine and other antipsychotics: a literature search and a pharmacovigilance study in VigiBase

INTRODUCTION

Antipsychotics (APs), during treatment or overdose, may be associated with respiratory aspiration.

AREAS COVERED

A PubMed search on September 30, 2022, provided 3 cases of respiratory aspiration during clozapine therapy and 1 case during an AP overdose. VigiBase records of respiratory aspiration associated with APs from inception until September 5, 2021, were reviewed. VigiBase, the World Health Organization's global pharmacovigilance database, uses a statistical signal for associations called the information component (IC).

EXPERT OPINION

The ICs (and IC₀₂₅) were 2.1 (and 2.0) for APs, 3.2 (and 3.0) for clozapine, 2.6 (and 2.4) for quetiapine, and 2.5 (and 2.2) for olanzapine. Cases of respiratory aspiration associated with APs included: 137 overdose/suicide cases (64 fatal) and 609 cases during treatment (385 fatal) including 333 taking clozapine (238 fatal). In logistic regression models of fatal outcomes, the odds ratios, OR, and (95% confidence intervals, CI) of significant independent variables were: a) 2.3 - 2.6 for clozapine in 3 samples of AP treatment of varying size, b) 1.9 (CI 1.0 to 3.5) for geriatric age in 284 patients on clozapine treatment, and c) 1.8 (CI 1.1 - 3.2) for antidepressant co-medication in 276 patients on non-clozapine APs. Multiple AP pharmacological mechanisms may explain respiratory aspiration.

Reflections on the Lack of Consideration of Ethnic Ancestry to Stratify Clozapine Dosing

This review article argues against trusting standard clozapine references, including the US package insert, because they do not include advances in the sciences of pharmacokinetics and pharmacovigilance and ignore the effects of ethnic ancestry on therapeutic dosing. The minimum therapeutic dose leading to the minimum therapeutic concentration of 350 ng/mL in serum/plasma can be used to compare individuals/groups with treatment-resistant schizophrenia. The US clozapine package insert recommends targeting doses of 300-450 mg/day and, subsequently, increments of up to 100 mg with a maximum dose of 900 mg/day. Ethnic ancestry is defined by DNA ancestry group. Asians (people with ancestry ranging from Pakistan to Japan) and Indigenous Americans are similar in clozapine dosing; their average clozapine minimum therapeutic dose ranged from 166 mg/day (female non-smokers) to 270 mg/day (male smokers). For those with European ancestry, average clozapine minimum therapeutic doses ranged from 236 mg/day (female non-smokers) to 368 mg/day (male smokers). Based on limited studies, Black (African sub-Saharan ancestry) patients may be treated with typical US doses (300-600 mg/day), assuming no poor metabolism (PM) status. Ancestry's impact on clozapine lethality in four countries is discussed (two countries with highly homogenous populations, Denmark and Japan, and two countries with increasingly heterogenous populations due to immigration, Australia and the UK). An international guideline with 104 authors from 50 countries/regions was recently published, providing 6 personalized clozapine titration schedules for adult inpatients (3 ancestry groups and PM/non-PM schedules) and recommending c-reactive protein monitoring at baseline and weekly for 4 weeks.

Clozapine Therapy and COVID-19: A Systematic Review of the Prevalence Rates, Health Outcomes, Hematological Markers, and Patient Perspectives

BACKGROUND/OBJECTIVES

There have been concerns that clozapine treatment may undermine the capacity of the body to fight infection and increase the vulnerability to contracting COVID-19. This review of recent cohort studies investigated (1) whether people with a severe psychiatric disorder are at increased risk of COVID-19 and complications, (2) the immunological response of clozapine-users who contract COVID-19, and (3) patients' perspectives on COVID-19 and the pandemic response.

METHODS

A systematic search of EMBASE, Medline, Pubmed, and PsycINFO databases using PRISMA guidelines using "COVID-19", "clozapine", and "vaccination" terms.

RESULTS

18 studies (out of 330 identified) met all criteria (N = 119 054 including 8045 on clozapine). There was no strong evidence that clozapine users may be at increased risk of contracting COVID-19 or developing complications after adjusting for medical comorbidities. Hematological studies showed temporary reductions in neutrophils in COVID-19-positive patients and vaccination suggesting a clozapine effect in defence against infection. Vaccination studies did not report major adverse effects. Increased plasma levels of clozapine and neutropenia however point to COVID-19-related interference of clozapine metabolism. Patient surveys reported limited impact on mental health and positive attitudes regarding pandemic response.

CONCLUSION

This review did not find compelling evidence that the immune system of clozapine users put them at risk of COVID-19 and further complications. Evidence of drug-infection interactions however points to the importance of adhering to consensus guidelines about clozapine therapy during the pandemic. More evidence using longitudinal designs is required to examine the longer-term effects of COVID-19 and vaccination in this vulnerable population.

Clozapine-induced myocarditis in children and adolescents: a pharmacovigilance study using VigiBase and a systematic literature review

INTRODUCTION

Clozapine-induced myocarditis in children (age ≤18 yo) was studied from a PubMed search (18 July 2022) (9 cases) and from the World Health Organization's pharmacovigilance database, called Vigibase, of adverse drug reaction (ADR) reports (72 non-duplicated cases). VigiBase uses a logarithmic measure of disproportionality called the information component (IC). A logistic regression model of presence/absence (40/32) of seriousness in VigiBase was developed.

AREAS COVERED

VigiBase provided a significant myocarditis IC = 4.2 with an IC₀₂₅ = 3.8; only 4 clozapine-induced myocarditis cases were expected, while 72 were observed. The PubMed search identified 9 cases, while VigiBase identified 72 cases (of which 67 did not overlap with published cases). These 76 combined cases included 35 doubtful (most with missing information on the day of diagnosis), 19 possible and 22 probable, according to the ADR scale. After adjusting for confounders, quetiapine increased the risk of seriousness with an odds ratio (OR) of 17.6 (95% confidence interval CI, 1.56 to 198.6), while Australian origin decreased it with an OR = 0.13 (CI, 0.04 to 0.47).

EXPERT OPINION

These 41 cases of at least possible clozapine-induced myocarditis indicated that this ADR can definitively occur in children, particularly in the first 30 days of up-titration. Children's and adult cases appeared similar.

Respiratory aspiration during treatment with benzodiazepines, antiepileptic and antidepressant drugs in the pharmacovigilance database from VigiBase

INTRODUCTION

Three psychotropic drug classes, benzodiazepines, antiepileptic drugs (AEDs) and antidepressants (ADs), whether used in treatment or overdose, may be associated with respiratory aspiration. Polypharmacy was defined by counting suspected drugs from these classes or two others, antipsychotics and opioids. The confounding effects of polypharmacy were considered in this study.

AREAS COVERED

VigiBase records of respiratory aspiration associated with benzodiazepines, AEDs, and/or ADs from inception until September 5, 2021, were reviewed. VigiBase, the World Health Organization's global pharmacovigilance database, uses a statistical signal for associations called the information component (IC).

EXPERT OPINION

The ICs (and IC₀₂₅) were benzodiazepines 2.8 (and 2.6), AEDs 1.6 (and 1.5), and ADs 1.4 (and 1.3). The cases of respiratory aspiration associated with at least one drug from these 3 classes included: 1) 553 cases absent any known overdose (2.8±1.7 drugs) and 2) 347 overdose cases (2.9±1.8 drugs). Little support for the association of respiratory aspiration and benzodiazepine, AED or AD monotherapy in therapeutic dosages was found. Studies of the association between benzodiazepine monotherapy and respiration aspiration are needed in geriatric patients. ADs added to other medications increased lethality in all cases of respiratory aspiration including those associated with overdose, polypharmacy and/or major medical problems.

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.

Screening the European pharmacovigilance database for reports of clozapine-related DRESS syndrome: 47 novel cases

Clozapine-related drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome is a rare adverse reaction. We aimed to screen a large pharmacovigilance database to identify clozapine-related DRESS cases, even if otherwise reported and provide a clinical overview. We screened spontaneous reports of clozapine-related DRESS syndrome in EudraVigilance database applying the European Registry on Severe Cutaneous Adverse Drug Reactions (RegiSCAR) criteria and scores to identify probable/definite DRESS syndrome cases. Clinical and demographic characteristics of included cases were provided and associations between RegiSCAR scores, and time to develop/recover DRESS were assessed. In a total of 262,146 adverse drug reactions reports for 75,190 clozapine-treated patients, 596 cases fulfilled RegiSCAR criteria; ultimately, 51 cases were rated as probable/definite DRESS according to RegiSCAR scores, of which 4 were previously published as case reports. The mean age of patients was 41.06 years (43.1% females), with 13 patients (25.5%) receiving reported co-medication with other DRESS culprit drugs. Median time between clozapine initiation and DRESS symptoms was 25 days. Clozapine dose was associated with days to develop symptoms (Spearman's ρ 0.40, p = 0.03). Organ involvement was reported in all cases followed by fever (n = 49; 96.1%) and eosinophilia (n = 47; 92.2%). Treatment involved clozapine discontinuation for 37 patients (72.5%), while 3.9% (n = 2) of cases ended fatally. Clozapine rechallenge was undertaken in 25 patients (49.0%). The screening of the EudraVigilance database revealed 47 novel clozapine-related DRESS cases, and only one was originally reported as DRESS. Clozapine-related DRESS may occur with clozapine monotherapy not only during dose titration, but also during maintenance treatment.

An international guideline with six personalised titration schedules for preventing myocarditis and pneumonia associated with clozapine

White blood cell (WBC) monitoring has reduced clozapine-treated patient deaths associated with agranulocytosis to a rarity. However, clozapine protocols and package inserts worldwide provide no instructions for preventing myocarditis or pneumonia during clozapine titrations. Prescribers worldwide are largely unaware of that. Meanwhile, as they worry about agranulocytosis, their clozapine-treated patients are at risk of dying from pneumonia or myocarditis. Consequently, an international guideline with 104 authors from 50 countries/regions was recently published to provide personalised clozapine titration schedules for adult inpatients. This forum article reviews pneumonia and myocarditis occurring during clozapine titration, as well as the three most innovative aspects of this new guideline: (1) personalised titration, (2) C reactive protein (CRP) measures, and (3) dose predictions based on blood levels. Clozapine metabolism is influenced by 3 levels of complexity: (1) ancestry groups, (2) sex-smoking subgroups, and (3) presence/absence of poor metabolizer status. These 3 groups of variables should determine the maintenance dose and speed of clozapine titration; they are summarised in a table in the full-text. The international clozapine titration guideline recommends measuring CRP levels simultaneously with WBC, at baseline and weekly at least for the first 4 weeks of titration, the highest risk period for clozapine-induced myocarditis.

Successful rechallenge after clozapine-associated myocarditis

Clozapine is a highly effective medication used in management of treatment-resistant schizophrenia. Clozapine-associated myocarditis (CAM) is a rare but increasingly recognised complication of clozapine titration. Following an episode of CAM, clinicians can face a challenging dilemma of balancing the risks of recurrent myocarditis against the harms of ongoing psychosis. We describe the case of a woman in her 60s who developed acute myocarditis during clozapine titration and was then cautiously rechallenged with a successful outcome.