Clozapine-Associated Neutropenia Prevalence in a Large, Integrated Healthcare System

Area of Science:

• Pharmacovigilance
• Hematology
• Psychiatry

Background:

• Clozapine is a vital antipsychotic, but carries a risk of neutropenia.
• The FDA removed the clozapine Risk Evaluation and Mitigation Strategies (REMS) program, impacting monitoring requirements.
• Understanding neutropenia prevalence post-REMS is critical for patient safety.

Purpose of the Study:

• To determine the incidence of clozapine-associated neutropenia.
• To identify patient-level factors linked to neutropenia.
• To inform safety protocols after FDA REMS program changes.

Main Methods:

• Retrospective cohort study of 402 adult patients initiating clozapine.
• Data extracted from electronic health records (sociodemographics, clinical data, ANC).
• Neutropenia defined as mild (ANC 1000-1499/μL) or severe (ANC < 1000/μL) within two years.

Main Results:

• 2.5% of patients experienced neutropenia; two cases were severe, one fatal.
• Significant racial differences observed in neutropenia occurrence (p=0.038).
• No significant associations found between neutropenia and patient-level factors.

Conclusions:

• Clozapine-related neutropenia is infrequent and often transient, yet potentially fatal.
• Continued adherence to manufacturer ANC monitoring guidelines is recommended.
• This study highlights the importance of ongoing vigilance despite regulatory changes.