Japanese patients need slower, personalized clozapine titrations: A comment on the case described by Kikuchi et al

When, Why and How to Re-challenge Clozapine in Schizophrenia Following Myocarditis

Clozapine-induced myocarditis (CIM) is among the most important adverse events limiting the use of clozapine as the most effective treatment for schizophrenia. CIM necessitates the immediate termination of clozapine, often resulting in its permanent discontinuation with considerable detrimental effects on patients' psychopathology and long-term outcome. Consequently, a clozapine re-challenge after CIM is increasingly regarded as a viable alternative, with published reports indicating a success rate of approximately 60%. However, published cases of re-challenges after CIM remain limited. Here, we provide a narrative review of the current state of research regarding the epidemiology, pathophysiology, risk factors, diagnosis and clinical management of CIM as well as a synthesis of current recommendations for re-challenging patients after CIM. This includes a step-by-step guide for this crucial procedure based on the current evidence regarding the pathophysiology and risk factors for CIM. Slow dose titration regimes and addressing risk factors including concomitant valproate and olanzapine are crucial both to prevent CIM and to ensure a safe and successful re-challenge. Furthermore, we discuss the utility of C-reactive protein, troponin, N-terminal-pro hormone and brain natriuretic peptide, therapeutic drug-monitoring and cardiac magnetic resonance imaging for CIM screening and diagnosis as well as for post-CIM re-challenges.

A Pharmacovigilance Study on Clozapine in the Food and Drug Administration Adverse Event Reporting System: A Regional Comparative Analysis

Objective

This pharmacovigilance study evaluated the profile of clozapine-related adverse events by region using the Food and Drug Administration Adverse Event Reporting System (FAERS).

Methods

We categorized each case into five regions (America, Europe/West Asia, Oceania, Asia, and Africa) based on the reporting country information in the FAERS database. The number of clozapine-related adverse events reported in each region was aggregated according to the preferred term (PT) and the Standardized Medical Dictionary for Regulatory Activities (MedDRA) Query (SMQ).

Results

A total of 101,872 clozapine-related adverse events were registered in the FAERS database. In America and Europe, leukocyte or neutrophil count abnormalities accounted for half of the top 10 PTs by relative reporting rate. However, Asia had higher relative reporting rates of pyrexia and salivary hypersecretion (13.91% and 10.85%, respectively). Regarding the SMQ, the relative reporting rates of infective pneumonia, convulsions, extrapyramidal syndrome, gastrointestinal obstruction, and hyperglycaemia/new onset diabetes mellitus were higher in Asia than in other regions (5.26%, 9.72%, 12.65%, 5.13%, and 8.26%, respectively), with significant differences even after adjusting for confounding factors using multivariate logistic regression analysis.

Conclusion

Spontaneous reports of adverse events associated with clozapine show regional disparities, particularly in Asia, where concentration-dependent adverse events are more frequently reported. However, the spontaneous reporting system has several limitations, requiring further research for validation.

Current practice for clozapine-induced leukopenia in Japanese psychiatric hospitals: A nationwide survey

Clozapine is an atypical antipsychotic used for treatment-resistant schizophrenia. In Japan, its use requires management by a blood monitoring system called the Clozaril Patient Monitoring Service (CPMS) for the early detection of serious side effects such as agranulocytosis, which is extremely rare. Monitoring services vary among the clozapine suppliers in different countries. Additionally, Japanese patients can be started on clozapine treatment exclusively through an 18-week inpatient admission at a psychiatric hospital capable of coordinating with a hematologist. One reported reason for the lack of widespread clozapine use in Japan is the difficulty in establishing collaboration with hematologists when agranulocytosis/leukopenia occurs. Hence, we conducted a nationwide web-based survey of CPMS-registered psychiatric facilities in Japan to determine the status of collaboration with hematology departments. Valid responses were received from the psychiatrists responsible for prescribing clozapine at 203 of the 547 facilities (response rate: 37.1 %). The largest number of psychiatric facilities (61 %) collaborated with hematologists at another facility with a psychiatry department, while psychiatrists in 32 % of the facilities worked with hematologists at their own facilities. Most patients with clozapine-induced agranulocytosis/leukopenia could be treated with clozapine discontinuation and follow-up in psychiatric inpatient units with the assistance of a hematologist. The actual workload of hematologists was limited, and the patients might experience the burden of repeated blood sampling. This study suggests that disseminating information regarding the status of collaborations with hematologists may promote the widespread use of clozapine in Japan. SHORT COMMENT FOR TWITTER: This study suggests that most patients with clozapine-induced agranulocytosis/leukopenia could be treated with clozapine discontinuation and follow-up in psychiatric inpatient units with the assistance of a hematologist.

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.

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.