Implications of Clozapine Monitoring During the COVID-19 Pandemic

Clozapine is the drug of choice for treatment-resistant schizophrenia. Routine monitoring of an absolute neutrophil count (ANC) is required to detect severe neutropenia, which is a black box warning for clozapine. However, during the COVID-19 pandemic, laboratory monitoring became less frequent because of decreased access to health care services and concern about increased viral exposure. The purpose of this study was to evaluate the discontinuation rate of clozapine due to severe neutropenia during the COVID-19 pandemic.

This 16-month retrospective study included all adult patients within the Veterans Health Administration who had a clozapine prescription at least 12 months before March 2020. Demographic data included indication for use, concomitant antipsychotic prescriptions, age, and race-ethnicity. Descriptive statistics were performed to analyze study objectives and demographic data.

In total, 2,106 patients were included in this study. No patients discontinued clozapine because of severe neutropenia, and only one patient had severe neutropenia during the study period. All-cause clozapine discontinuation occurred for 96 patients (5%). Significant differences were found between individuals who discontinued clozapine and those who did not for the longest ANC gap category (p<0.001), neutropenia category (p=0.042), and duration of clozapine use (p=0.001).

Less frequent ANC monitoring as a consequence of the COVID-19 pandemic did not lead to increased incidence of clozapine discontinuation due to severe neutropenia. These results demonstrate the feasibility and safety of extended-interval laboratory monitoring (i.e., every 90 days) for patients receiving clozapine treatment for at least 1 year.