The adverse effects of clozapine on blood markers and electrocardiographic findings in patients with schizophrenia.

INTRODUCTION

Clozapine remains the gold-standard antipsychotic for treatment-resistant schizophrenia, but its use is hindered by rare but serious adverse effects, such as hematologic abnormalities and myocarditis.

PURPOSE: This study investigated the adverse impacts of clozapine on blood markers and electrocardiographic (ECG) findings among patients with schizophrenia, emphasizing in early detection of life-threatening complications.

METHODS

All patients initiated on clozapine at a psychiatric hospital in Athens, Greece, between January 2022 and June 2024 were considered for inclusion. Thirty-one patients with complete clinical and laboratory data were monitored for hematological, biochemical, and ECG changes at baseline, days 5-10, and after 1-2 months. Parameters evaluated included white blood cell (WBC) counts, differential counts, C-reactive protein (CRP), hepatic enzymes, creatine phosphokinase (CPK), troponin, and ECG changes.

RESULTS

Of the 31 patients, two (6.5%) developed clozapine-induced myocarditis within the first three weeks, confirmed by clinical symptoms, ECG abnormalities, and elevated troponin levels, necessitating immediate clozapine discontinuation. Four patients exhibited prolonged QTc, two overlapping with myocarditis cases. Eleven experienced elevated CRP, while eosinophilia and transient hepatic or muscular enzyme elevations were also common, especially during rapid titration phases; indicating inflammatory responses or mild organ involvement. No cases of agranulocytosis or severe eosinophilic complications occurred.

CONCLUSIONS

Clozapine can induce significant hematologic, inflammatory, hepatic, muscular, and cardiac adverse effects, particularly during rapid titration. Systematic monitoring of blood markers and ECGs was vital in early detection and management of these complications, especially myocarditis. The findings underscore the importance of cautious titration protocols and tailored surveillance strategies to enhance clozapine safety in clinical practice.