Clozapine-induced Myocarditis in Korea: Analysis of a Nationwide Database and Comparison to Other Countries

Clozapine, though the mainstay treatment for treatment-resistant schizophrenia, is associated with potentially fatal adverse reactions, including myocarditis. The incidence of clozapine-induced myocarditis (CIM) demonstrates geographic and ethnic variability; however, reports from Asia remain scarce. This study aimed to provide a comprehensive overview of CIM in Korea and compare findings with reports from other countries.

CIM cases were identified from Korean National Health Insurance Service (NHIS) database based on diagnostic codes, prescription timelines, and clinical details. Patient characteristics and concomitant medications were analyzed. A PubMed search using a validated query was conducted to compare CIM in Korea with those reported in other regions.

From the NHIS database of 36,286 patients with schizophrenia spectrum disorders who were prescribed clozapine, 29 patients (0.08%) received myocarditis diagnosis. Among them, 9 patients (0.02%) who discontinued clozapine after the diagnosis could be considered probable CIM. Among these probable CIM cases, 4 male patients (0.01%) developed myocarditis within 30 days of clozapine initiation, while 5 patients developed myocarditis during the maintenance period. Two patients were found to have died from CIM. The literature review yielded 38 relevant articles on CIM incidence, including 4 from Asia, 4 from Europe, 3 from the Americas, 16 from Australia, and 4 from New Zealand. A comparison between countries demonstrated a lower incidence of CIM in Korea.

Consistent with the previous report, the incidence of CIM in Korea was less than 0.1%, which is lower than the incidences in other countries.