Clozapine is a type of antipsychotic medicine used for treatment-resistant schizophrenia patients and for schizophrenia patients who have severe, untreatable neurological adverse reactions to other antipsychotic agents. The risk of agranulocytosis associated with clozapine use is minimized through routine hematological monitoring.
New evidence from the European Medicines Agency (EMA) has been issued with revised routine blood count monitoring recommendations, based on findings showing that the risk of clozapine-induced neutropenia and agranulocytosis is highest in the early stages of treatment.
The main changes include the removal of white blood cell (WBC) monitoring, as absolute neutrophil count (ANC) alone is considered sufficient. ANC monitoring frequency during the first year of treatment remains the same, with weekly ANC checks for the first 18 weeks followed by monthly monitoring for the remainder of the first year.
For stable patients without a history of neutropenia during the first year, monitoring may be reduced to once every 12 weeks after one year and annually after two years. In addition, ANC thresholds for treatment have been revised, with clozapine recommended only for patients with ANC above certain thresholds.
Blood monitoring has been found to be an important factor in the underutilization of clozapine and therefore, the reduction of long-term monitoring requirements may lower practical barriers to initiating clozapine treatment, potentially broadening access and adoption of the drug in eligible patients.
While monitoring requirements are adjusted for stable patients, the need for frequent and reliable testing at initiation and during early treatment remains unchanged, where testing intensity is at its highest.
Key Takeaways:
The revised monitoring recommendations reflect new evidence showing a decreased risk over time. Updated hematological monitoring for clozapine is both safe and evidence-based, enabling less stringent long-term follow-up without compromising care.
These changes can reduce logistical burdens for both patients and healthcare services, while potentially increasing the uptake and continuation of clozapine among eligible patients—an important benefit given clozapine’s superior effectiveness in treatment-resistant schizophrenia (TRS).
HemoCue remains fully committed to supporting safe clozapine therapy through accurate, rapid, and accessible point-of-care blood testing. Together, we can strengthen our commitment to improving outcomes for patients living with severe mental illness.
Read the full publication here:
Revised recommendations for routine blood count monitoring for the risk of agranulocytosis
References:
European Medicines Agency, Clozapine-direct healthcare professional communication. Clozapine: revised recommendations for routine blood count monitoring for the risk of agranulocytosis.
https://www.ema.europa.eu/en/medicines/dhpc/clozapine#about.
Accessed March 24, 2026.
Nielsen et al. Psychiatrists’ attitude towards and knowledge of clozapine treatment
Journal of Psychopharmacology 2010, 24(7): 965–971.
