Long-term persistence of the risk of agranulocytosis with clozapine compared with other antipsychotics: a nationwide...

Area of Science:

• Psychiatry and Pharmacology
• Hematology
• Public Health & Epidemiology

Background:

• Clozapine is the sole effective treatment for treatment-resistant schizophrenia.
• Agranulocytosis is a severe, life-threatening adverse effect of clozapine.
• The long-term risk profile of clozapine-induced agranulocytosis requires further elucidation.

Purpose of the Study:

• To investigate the long-term risk of clozapine-induced agranulocytosis.
• To compare the incidence and risk of agranulocytosis between clozapine and non-clozapine antipsychotic treatments over an extended period.

Main Methods:

• A population-based cohort study in Finland (1972-2014) identified patients with schizophrenia or schizoaffective disorder.
• Kaplan-Meier models and nested case-control models were used to analyze the time to agranulocytosis diagnosis.
• Adjusted odds ratios (aORs) were derived to compare risks associated with varying durations of clozapine and non-clozapine antipsychotic use.

Main Results:

• The cumulative incidence of agranulocytosis was 1.37% on clozapine versus 0.13% on non-clozapine antipsychotics.
• The risk of clozapine-induced agranulocytosis decreased significantly with duration of use, from an aOR of 36.01 (less than 6 months) to 4.38 (54+ months).
• The lethality rate for clozapine-induced agranulocytosis was very low (1 death in 3559 individuals).

Conclusions:

• While the risk of clozapine-induced agranulocytosis diminishes over time, it may persist at a higher level compared to non-clozapine antipsychotics.
• The absolute long-term excess risk appears small relative to clozapine's benefits, including improved life expectancy.
• Consideration should be given to potentially relaxing long-term neutrophil monitoring to facilitate clozapine use and its associated survival benefits.