A case report on the effects of COVID-19 on ANC monitoring in a patient on long-term clozapine treatment

BACKGROUND: Clozapine carries a US boxed warning for severe neutropenia, and strict monitoring is required through the FDA's Risk Evaluation and Mitigation Strategy (REMS) program. Patients with confirmed diagnosis of COVID-19 are also at risk for neutropenia. For patients on clozapine, the diagnosis of this novel virus may require an increase in the frequency of scheduled ANC monitoring. A case report of moderate neutropenia following COVID-19 diagnosis that required an increase in the frequency of ANC monitoring in a patient on long-term clozapine treatment is discussed. CASE REPORT: A 33-year-old white man with schizophrenia had been on clozapine for more than 2 years, with an ANC monitoring schedule once every 4 weeks. The patient was admitted to the hospital for worsening aggressive behavior. On day 11 of hospital admission, he tested positive for COVID-19. Five days following this diagnosis, the patient's ANC dropped from 2.2/L to 0.8/L. This decrease led to daily ANC labs and the clozapine regimen being held for 1 day. Throughout the patient's admission adjustments were made to the frequency of lab monitoring based on fluctuations in his ANC levels. DISCUSSION: There have been limited case reports on patients receiving clozapine experiencing neutropenia following the diagnosis of COVID-19. To the authors knowledge, this is the first case report from the United States that specifically discusses the required changes to ANC monitoring. CONCLUSIONS: Patients on clozapine who test positive for COVID-19 may be at an even greater risk for neutropenia, compared with clozapine patients without COVID-19. Increasing the frequency of ANC monitoring should be considered in the weeks following the diagnosis to ensure that clozapine treatment can be safely adjusted, or even discontinued.