[Hematologic Monitoring During Long-Term Clozapine Treatment: Retrospective Data from Chilean Patients with...

Clozapine is the most effective treatment for resistant schizophrenia, although its use is limited by the risk of hematological adverse effects, especially neutropenia. However, there are scarce data from populations in our environment, especially from long-term follow-up.

To determine the incidence of hematological alterations in patients with schizophrenia under chronic treatment with clozapine at the Hospital del Salvador de Valparaíso.

Retrospective observational study that analyzed 31,430 hemograms of 358 patients treated with clozapine at the Hospital del Salvador de Valparaíso between 2002 and 2020. The presence of leukocytosis, eosinophilia, anemia, thrombocytosis, thrombocytopenia and neutropenia was evaluated according to MINSAL criteria. Duration, recurrence and distribution by sex and age and frequency of alterations in relation to chronic use of the drug were described.

The most frequent alterations were leukocytosis (74%), eosinophilia (62%) and anemia (32%). The least common were thrombocytopenia (17%), thrombocytosis (17%) and neutropenia (6.2%). Most events occurred after the first year of treatment, with high recurrence in leukocytosis (79%) and eosinophilia (69%). Neutropenia was predominantly mild and transient, with no severe cases after the first year. Differences by sex were observed in the prevalence of anemia (more frequent in women), but not in other alterations.

Hematological alterations in Chilean patients on chronic clozapine treatment are frequent and recurrent but mostly benign. The low incidence of severe neutropenia, especially after one year of treatment, supports the revision of current monitoring protocols, which could be limiting access to this drug, but more data from the local population are required to guide clinical and health policy decisions in the region.