Clozapine, agranulocytosis, and benign ethnic neutropenia

Current knowledge and clinical implications Clozapine is an atypical antipsychotic that is effective in treatment resistant schizophrenia.1 The National Institute for Health and Clinical Excellence (NICE) guidelines for schizophrenia specify that “in individuals with evidence of treatment resistant schizophrenia, clozapine should be introduced at the earliest opportunity”.2 A severe adverse effect of clozapine that limits its more widespread use is agranulocytosis. Patients who are taking clozapine need to have their full blood counts (FBC) monitored regularly, and if the total white cell and/or neutrophil counts indicate agranulocytosis, clozapine prescription must be terminated. Among certain ethnic groups, a significant proportion of people have a low baseline neutrophil count. This is called benign ethnic neutropenia (BEN). This editorial looks at the important issues associated with agranulocytosis and BEN in patients receiving clozapine. Agranulocytosis occurs in about 1% of patients taking clozapine.3,4 Neutropenia is seen in about 3%.4 The risk of both agranulocytosis and neutropenia is highest between 6 weeks and 18 weeks after starting clozapine treatment.4 Hence, in the United Kingdom and …