Incidence and Management of Clozapine-Induced Myocarditis in a Large Tertiary Hospital.

Objective: Clozapine, an antipsychotic reserved for management of treatment-resistant schizophrenia, is associated with severe adverse effects, including myocarditis. This study aims to determine the incidence of clozapine-induced myocarditis at a large tertiary hospital compared to what is reported in the literature.

Methods: Medical records of adult patients admitted to psychiatry units receiving clozapine between January 1, 2010, and July 31, 2016, were retrospectively reviewed. Cases of clozapine-induced myocarditis were defined as having elevated C-reactive protein (CRP) or detectable troponin and at least 1 sign or symptom of myocarditis, in the absence of alternative plausible aetiologies. The primary outcome was incidence of clozapine-induced myocarditis during the study period. Secondary outcomes included rate and description of the management of clozapine-induced myocarditis.

Results: In total, 316 patients were screened; 10 patients met the case definition for clozapine-induced myocarditis. The incidence of this adverse drug reaction over the study period was 3.16%. Reduced left ventricular ejection fraction was observed in 60% of cases, and electrocardiography changes were noted in 60% of cases. Clozapine was discontinued in all cases. Rechallenge was performed in 2 patients; recurrent CRP elevation resulted in discontinuation in each case. Medications for management of myocarditis were used in 50% of cases. Although 2 patients required transfer to critical care, the in-hospital mortality rate was 0%.

Conclusions: The incidence of clozapine-induced myocarditis at the study hospital was consistent with the higher range reported in the literature. Further research is necessary to elucidate risk factors, definitive diagnostic criteria, and effective management of clozapine-induced myocarditis.