The Modernization of Clozapine: A Recapitulation of the Past in the United States and the View Forward

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.

Letter to the FDA Proposing Major Changes in the US Clozapine Package Insert Supported by Clozapine Experts Worldwide. Part I: A Review of the Pharmacokinetic Literature and Proposed Changes

PURPOSE/BACKGROUND

Clozapine was approved in the United States (US) using 1989 regulations and knowledge. After 30 years, many sections of the US package insert (PI) are outdated.

METHODS

We comprehensively reviewed the literature to propose PI updates. We present the information in 2 articles. In Part I, we focus on basic pharmacology based on 407 relevant articles. Part II focuses on clinical aspects and pharmacovigilance.

FINDINGS/RESULTS

Based on more recent expectations of Food and Drug Administration regulations, we reviewed clozapine basic pharmacology including the following: 1) clearance, 2) pharmacokinetics and pharmacodynamics, and 3) monitoring tools. We identified 9 major problems in the basic pharmacological sections of the PI including the following: 1) in vivo studies indicate that clozapine is dependent on CYP1A2 for its metabolism, 2) the minor role of CYP2D6 in clozapine metabolism requires removing the PI recommendation to lower clozapine doses in CYP2D6 poor metabolizers, 3) in nontoxic concentrations CYP3A4 has a minor role in clozapine metabolism and potent CYP3A4 inhibitors lack clinically relevant effects, 4) several drug-drug interactions need to be updated based on recent literature, 5) systemic inflammation may decrease clozapine metabolism and increase the risk of clozapine intoxication, 6) obesity may decrease clozapine metabolism, 7) patients of Asian and Indigenous American ancestry need lower clozapine doses, 8) personalized titration and c-reactive protein monitoring should be considered until prospective studies are available, and 9) the half-life section needs to be modified to acknowledge that single dosing at night is frequent in the US.

IMPLICATIONS/CONCLUSIONS

An improvement in the US clozapine PI may lead to improvement in PIs worldwide.

Elimination of the clozapine risk evaluation and mitigation strategy (REMS) - Improving access to care for those with treatment-refractory schizophrenia

A variety of pharmacological treatment options exist for schizophrenia, although as many as 20 % to 40 % of individuals with schizophrenia experience treatment-refractory symptoms. Typically defined by non-response to at least two sequential, adequate trials of antipsychotics, treatment-refractory schizophrenia represents a significant clinical challenge. Currently, clozapine (Clozaril) is the only evidence-based treatment strategy available for treatment-refractory schizophrenia. Nonetheless, clozapine has long remained underutilized due to administrative barriers such as the Food and Drug Administration (FDA) Risk Evaluation and Mitigation Strategy (REMS) program, a historical requirement for clozapine prescribing. The FDA has eliminated the clozapine REMS program effective February 2025. This editorial provides an update on clozapine and recognizes that elimination of the clozapine REMS program will reduce barriers to clozapine prescribing.

Clozapine-Induced Acute Pericarditis and Cardiac Tamponade: Early Recognition Improves Clinical Outcomes

Clozapine is approved for treatment-resistant schizophrenia. Many cardiovascular side effects are associated with clozapine, including QTc prolongation and myocarditis, which is a black box warning. Few cases of pericarditis have been reported in recent literature. We report a case of a 26-year-old male with schizoaffective disorder who presented with sharp chest pain and shortness of breath. The patient was started on clozapine three months prior to his current presentation. The workup revealed a large pericardial effusion with cardiac tamponade physiology and signs consistent with acute pericarditis. He required emergent pericardiocentesis and pericardial drain placement. Symptoms resolved after treatment with ibuprofen and colchicine. This case report highlights the importance of early diagnosis of life-threatening cardiovascular complications associated with clozapine, especially acute pericarditis and cardiac tamponade due to pericardial effusion. We strongly recommend implementing monitoring protocols to prevent this potentially life-threatening adverse effect in patients taking clozapine.

Physician Experiences With and Perspectives on Clozapine Prescribing

Importance

Clozapine is an effective medication for treatment-resistant schizophrenia but can cause agranulocytosis. Since its approval, patients taking clozapine have been required to undergo regular blood testing to screen for neutropenia. In 2015, the risk management programs were merged into a single risk evaluation and mitigation strategy (REMS), which mandates that prescribers undergo a certification process in which they attest to understanding the risk of agranulocytosis and commit to performing required blood testing. It is unknown how the clozapine REMS program has affected clinical practice.

Objective

To understand physicians' perceptions of and experiences with the clozapine REMS program.

Design, Setting, and Participants

This survey study included US physicians who prescribed clozapine in 2021 or 2022. A 57-question, closed-field questionnaire was administered via paper or online. The first survey wave took place from May to October 2022 and the second from October 2022 to January 2023.

Exposures

Gender, race and ethnicity, practice specialty, practice setting, practice region, professional time in clinical practice, years since graduation from medical school, and number of patients prescribed clozapine in the past 3 years.

Main Outcomes and Measures

Experiences with and perceptions of the REMS certification process, patient initiation, and the REMS safe use requirements were measured using Likert scales. Descriptive statistics and multivariable modeling were used to analyze the study results.

Results

Of 750 physicians contacted, 196 responded (30% response rate). Most respondents were male (129 [67%]), most identified as Asian (48 [25%]) or White (124 [63%]), and most were psychiatrists (165 [86%]); almost half (88 [45%]) practiced in an outpatient group setting. Most respondents reported that the information provided during certification was clear (179 [92%]) and contained useful drug information (145 [75%]) and that the paperwork associated with required blood testing facilitated physician-patient conversation (102 [53%]). Most respondents wanted certification materials to include all clinically important risks (172 [89%]) and benefits (139 [72%]) and reported frequent delays in medication access owing to required blood testing (115 [60%]). Two-thirds of respondents agreed that the positives of the certification process (123 [64%]) and blood testing requirements (129 [68%]) outweighed the negatives. In multivariable analysis, negative REMS perceptions were less common among physicians in practice longer (≥35 vs <15 years since medical school: odds ratio [OR], 0.28; 95% CI, 0.10-0.80) and among American Indian or Alaska Native, Black, and Native Hawaiian or Other Pacific Islander physicians compared with White physicians (OR, 0.08; 95% CI, 0.01-0.73).

Conclusions and Relevance

In this survey study of physician prescribers of clozapine, a majority were satisfied with the clozapine REMS program but highlighted the need for enhanced educational materials and administrative efficiency.

The timing and severity of clozapine-associated neutropenia in the US: Is the risk overstated?

BACKGROUND

Concern about clozapine-associated neutropenia contributes to clozapine's underutilization and racial disparities in access. People with African ancestry are more likely to have lower normative absolute neutrophil counts (ANC), associated with the Duffy null genetic polymorphism. Recent data on clozapine-associated neutropenia in the US are lacking.

METHODS

Patients prescribed clozapine in the Johns Hopkins Medicine electronic medical record (EMR) between 2013 and 2023 were identified. Duffy null Associated Neutrophil Count (DANC) was assigned if there were two ANC's < 2000 cells/μL, >30 days apart, before starting clozapine. Rates of neutropenia, timing of first neutropenia, and demographic differences were explored.

RESULTS

974 received clozapine and had ANC's available, with 63.9 % male, 51.1 % White, and 39 % Black. 287 were presumed to start clozapine during the study period, and were 62.4 % male, 46 % White, and 44.9 % Black. No patients developed severe neutropenia. 59 (6.1 %) developed mild or moderate neutropenia. 19 (6.6 %) new starts had presumed DANC, and none developed neutropenia. 11 of 16 presumed new starts who developed neutropenia did so within eight months. No demographic differences were found between groups for presumed new starts. For non-new starts, where DANC assignment was not possible, Black patients were more likely than White patients to develop neutropenia (OR 3.48, 95 % CI [1.65, 7.73]).

DISCUSSION

To our knowledge, this is the first observational study of clozapine-associated neutropenia in the US in the past decade, and it includes a substantial proportion of Black patients. ANC monitoring requirements may be too strict, contributing to clozapine underutilization.

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.

The potential influence of estrogen-containing oral contraception on clozapine metabolism in a patient with known pharmacogenomic status

Clozapine is primarily metabolized via cytochrome P450(CYP)1A2 and to a lesser extent CYP3A4, CYP2C19, and CYP2D6. Metabolic inhibitors of clozapine, such as fluvoxamine and ciprofloxacin, are important to recognize to avoid adverse drug events. Estrogen-containing oral contraceptives (eOCPs) are weaker CYP1A2 and CYP2C19 inhibitors but are associated with a 2-fold increase of clozapine concentrations. The potential for phenoconversion due to a CYP genetic polymorphism can add additional complexities when considering drug interactions. A case report is presented of a suspected interaction between newly initiated clozapine and a prescribed eOCP for which the patient's pharmacogenomic status was known. A 17-year-old, nonsmoking, White female with a history of schizophrenia was initiated on clozapine 12.5 mg at bedtime with a plan to increase by 25 mg every 4 days in the outpatient setting. The patient was a known rapid CYP1A2 metabolizer without identified sources of CYP1A2 induction and a CYP2C19 rapid metabolizer. Based on pharmacogenomic testing, there was no suspicion for significant gene-drug interactions. Yet, as the patient was prescribed an eOCP, a clozapine concentration was obtained after reaching 150 mg at bedtime. This steady-state clozapine concentration was found to be 560 ng/mL, correlating with worsening sedation and constipation. Given ongoing side effects, clozapine was lowered to 100 mg at bedtime; however, ongoing intolerance ultimately led to clozapine discontinuation. This case highlights the potential interaction between clozapine and eOCP in a CYP1A2 and CYP2C19 rapid metabolizer, leading to clozapine intolerance and discontinuation. The concomitant use of clozapine and eOCPs should be undertaken judiciously.

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.

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.

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.

Categorical and Dimensional Approaches for Psychiatric Classification and Treatment Targeting: Considerations from Psychosis Biotypes

Categorical diagnosis, a pillar of the medical model, has not worked well in psychiatry where most diagnoses are still exclusively symptom based. Uncertainty continues about whether categories or dimensions work better for the assessment and treatment of idiopathic psychoses. The Bipolar Schizophrenia Network for Intermediate Phenotypes (B-SNIP) examined multiple cognitive and electrophysiological biomarkers across a large transdiagnostic psychosis data set. None of the variables supported neurobiological distinctiveness for conventional clinical psychosis diagnoses but showed a continuum of severity. Using numerical taxonomy of these data, B-SNIP identified three biological subtypes (Biotypes) agnostic to DSM diagnoses. Biotype-1 is characterized by reduced physiological response to salient stimuli, while Biotype-2 showed accentuated intrinsic (background or ongoing) neural activity and the worst inhibition. Biotype-3 cases are like healthy persons on many laboratory measures. These Biotypes differed in imaging and other electrophysiological measures not included in subgroup creation, illustrating external validation. The Biotypes solution also replicated in an independent sample of psychosis cases. Biotypes are differentiable by clinical characteristics, leading to a feasible algorithm for Biotype estimates. Identifying Biotypes may aid treatment selection and outcome prediction. As an example, preliminary cross-sectional B-SNIP data suggest that Biotype-1 cases may have physiological features that predict a more favorable response to clozapine. While psychosis Biotypes reveal physiological heterogeneity across cases with similar clinical characteristics, data also suggest a dimensional vulnerability for serious psychopathology that cuts across diagnostic boundaries. Both categorical and dimensional diagnostic approaches should be considered within idiopathic psychosis for optimum diagnosis, care, and research.

A systematic review of clozapine-associated inflammation and related monitoring

Clozapine is an effective antipsychotic medication used for treatment-resistant schizophrenia. However, it is underutilized due to rigorous hematologic monitoring requirements and many adverse drug reactions. Publications have highlighted the occurrence of inflammatory reactions, some life-threatening, particularly during the early stages of clozapine treatment. Although guidelines have suggested monitoring for inflammatory processes during clozapine initiation, screening in clinical practice is not universal. This systematic review aimed to investigate the relationship between clozapine and inflammation and assess the importance of monitoring for inflammatory reactions. A comprehensive literature search yielded 6915 unique publication records after removal of duplicates. After a rigorous screening process, 75 publications were included in the review, which focused on three main aspects: (i) the impact of clozapine on inflammatory markers, (ii) monitoring cardiac and other organ function during clozapine-associated inflammatory processes, and (iii) monitoring non-specific signs and symptoms of inflammation. Elevated levels of C-reactive protein (CRP) and several proinflammatory cytokines have been observed in association with clozapine treatment. However, the practicality of measuring specific markers in clinical practice remains uncertain. Current evidence supports monitoring CRP levels during the first 4-8 weeks of treatment, especially to facilitate myocarditis screening. Further research is needed to establish clinically relevant CRP thresholds for intervention. The implementation of monitoring protocols during the early phase of clozapine treatment may mitigate adverse reactions and allow for continued use of clozapine. Future studies should also explore the association between clozapine-associated inflammation and pneumonia, as well as investigate the impact of inflammation on clozapine metabolism to predict the need for dose adjustment. These endeavors may facilitate the development and implementation of evidence-based guidelines for the monitoring of clozapine-associated inflammation.

Ethnopsychopharmacology: Clinical and scientific writing pearls

The concept of ethnopsychopharmacology aims to predict or explain the pharmacologic response to psychiatric medications based on the influence of biologic and nonbiologic factors. Interactions involving these factors are complex and influence patient outcomes in health care. Pharmacists and other clinicians working in patient care environments, research, or medical education should engage in lifelong learning to enhance ethnopsychopharmacologic knowledge gaps, which ultimately may improve and individualize care across diverse populations. Through two cases, this paper provides pearls on how biogeographical ancestry and cytochrome P450 status may influence pharmacotherapy selection, dosing, or response. A third scenario highlights a publication, like many other published works, with deficiencies in how data on ancestry, race, and ethnicity are collected or reported. Current recommendations on the use of inclusive language in scientific writing are reviewed, with attention to specific examples.

Diltiazem for clozapine-induced generalized hyperhidrosis

Background

Clozapine can be associated with significant side effects and tolerability issues. Hyperhidrosis occurs less commonly and is unanticipated by clinicians because of clozapine's significant anticholinergic activity.

Case Report

A 34-year-old female developed clozapine-induced nocturnal, generalized hyperhidrosis following initial titration to 400 mg/day. Dose reduction did not decrease the side effect. Treatment with an anticholinergic medication could not be initiated because of constipation. Treatment with a beta blocker resulted in worsening of asthma. Treatment with a calcium channel blocker, diltiazem CD 180 mg/day, resulted in a significant reduction in hyperhidrosis.

Conclusion

This case supports the use of calcium channel blockers to reduce clozapine-induced hyperhidrosis and offers an alternative to anticholinergic medications that may negatively impact clozapine tolerability.

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-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.