Olanzapine induced Neutropenia: A Case Report

BACKGROUND: Antipsychotic medications remain the mainstay in the treatment of schizophrenia. Haematological side effects of antipsychotics are not commonly reported. Neutropenia or agranulocytosis is commonly associated with Clozapine, though an increased risk for leukopenia/neutropenia have been suggested with Olanzapine, Risperidone and Chlorpromazine. We report a patient with schizophrenia who developed reversible neutropenia on treatment with Olanzapine. CASE PRESENTATION: A 30-year-old man, presented to the outpatient clinic, three years ago, with one year history of psychotic symptoms. A diagnosis of schizophrenia was considered and his symptoms remitted with Olanzapine 25 mg per day. He did not have any medical comorbidities. Following discontinuation of medications, he presented with a relapse of symptoms. In view of good response in the past, he was restarted on Olanzapine as baseline investigations were normal. During titration of Olanzapine, at 15 mg/day, his total white blood cell counts reduced to 2700/mm(3) with absolute neutrophil count of 1215/mm(3). In consultation with a haematologist, medical causes for neutropenia were ruled out. A possibility of Olanzapine induced neutropenia was considered. Olanzapine was stopped and Haloperidol trial was initiated, following which cell counts normalized in a week. DISCUSSION: Various mechanisms have been proposed for Olanzapine associated neutropenia including direct toxicity or even immune mediated. A previous report has documented cross sensitization between Clozapine and Olanzapine. This patient developed neutropenia despite tolerating Olanzapine previously. Hence sensitization during the previous trial is a possibility. This report adds to the existing knowledge about haematological side effects of Olanzapine and should inform clinical practice.