Original Publication Date: >9 July, 2015
Publication / Source: Pharmacogenomics
Authors: Moira Verbelen & Cathryn M Lewis
The antipsychotic clozapine is reserved for treatment resistant schizophrenia patients despite its proven superior efficacy, because 0.8% of treated patients develop agranulocytosis, an adverse drug reaction [1–3]. Agranulocytosis is a hematological condition in which the number of neutrophils is severely reduced (less than 500 cells/mm³ of blood), which renders the patient susceptible to infections and is fatal in 2–4% of agranulocytosis cases . This severe adverse event is not dose dependent and few risk factors have been identified, although older age and female gender increase risk slightly [2,5]. Around 80% of agranulocytosis cases occur in the first 18 weeks of clozapine treatment and the risk reduces by a factor of ten after the 1st year [1,2]. To improve safety, patients treated with clozapine are required to undergo regular white blood cell counts throughout the course of treatment.