Evaluating the Effect of the Changes in FDA Guidelines for Clozapine Monitoring

Concerns exist that clozapine is underutilized in the management of treatment-resistant schizophrenia. Although a 2015 change in the US Food and Drug Administration (FDA) monitoring recommendations lowered the threshold of the absolute neutrophil count for treatment interruption from 1,500/μL to 1,000/μL and removed white blood cell count thresholds from the monitoring algorithm, the implications of this policy change on clozapine interruptions remain unknown.

We analyzed outpatient prescribing records for antipsychotic medications in the Veterans Integrated Service Network 7 (VISN 7) database between 1999 and 2012 to assess the potential impact of the recent changes in FDA neutropenia monitoring recommendations on clozapine treatment discontinuation. We evaluated results of complete blood count monitoring to compare percentages of patients who developed or would have developed ≥ 1 hematologic event under the previous and current FDA guidelines in the first year following initiation of clozapine.

From a cohort of 14,620 patients with schizophrenia (ICD-9-295.x), 246 patients received clozapine treatment (1.7%). No agranulocytosis was observed during the study period. Under the former recommendations, 5 patients in the clozapine initiation cohort (n = 160, 3.1%; 95% CI, 0.43-5.83) qualified for treatment interruption during the first year of clozapine treatment, while only 1 patient (0.6%) qualified under the current recommendations. Under the former recommendations, hematologic events occurred at a similar rate for individuals taking and not taking clozapine.

While clozapine remains an underused medication, the new FDA monitoring guidelines are likely to substantially reduce the percentage of patients who meet criteria for clozapine-associated hematologic events requiring treatment interruption. This decrease may reduce the clinical burden of managing patients on clozapine and therefore increase the number of individuals treated with this uniquely effective medication. However, prospective studies of individuals treated under the new guidelines are needed to fully assess safety of the FDA's change.