Monitoring for myocarditis during treatment initiation with clozapine.

Objective: Clozapine use is associated with myocarditis. In this study, we investigated what clinical signs and symptoms, and/or laboratory test(s), alert clinicians to presumptive myocarditis (PrMy) most accurately and at the earliest time point. We also investigated the incidence of PrMy during the initial exposure to clozapine versus in patients restarted on clozapine after extended interruption of prior prolonged treatment.

Methods: 100 patients admitted to state psychiatric hospital started on clozapine were recruited into the study. 76 patients were treated with clozapine for the first time and 24 patients were restarts. Creatine kinase (CK), troponin I (TROP), eosinophil count (EOS), and C-reactive protein (CRP) were obtained at baseline and weeks 1, 2, 3, and 4. Descriptive statistics were calculated for demographic and clinical variables. Student's t test and chi-squared test were used to compare means and proportions between initial exposure and restart groups.

Results: Clinical features and laboratory tests suggestive of PrMy were seen in 4 patients (5.3%) in initial exposure group and none in restart group. 3.5% of TROP levels were abnormal in initial exposure group and no abnormal levels were found in the restart group. 30% and 46% of CK, 23% and 39% of CRP, and 14% and 23% of EOS were abnormal in initial exposure group and restart groups, respectively.

Conclusions: PrMy was common (5.3%) during clozapine initiation. Prospective management through serial laboratory monitoring with weekly TROP levels was sensitive enough to allow for timely clozapine discontinuation.