Smith RL, et al. - The relationship between concentrations of N-desmethylclozapine, the major stable clozapine metabolite, and absolute neutrophil granulocyte count (ANC) were examined in a real-life population of clozapine-treated patients. In this real-life population of schizophrenia patients, N-Desmethylclozapine level and ANC significantly correlated. The positive correlation could reflect reduced clozapine availability for the formation of reactive metabolites potentially affecting granulocyte level, which was also present in the metabolic ratio. However, this hypothesis needed to be studied further in clozapine-treated patients with neutropenia or agranulocytosis as the findings were based on ANC mainly within the reference range.