As-Required Filgrastim for Late-Onset Neutropenia Complicating Long-Term Clozapine Treatment: a Case Report.

Clozapine is considered the most effective antipsychotic for schizophrenia, but it can cause neutropenia and even agranulocytosis. We describe the first case in Hong Kong involving the use of filgrastim, a recombinant form of human granulocyte colony-stimulating factor, to enable clozapine continuation therapy for a severely ill patient with treatment-resistant schizoaffective disorder who developed recurrent neutropenia after almost 20 years of continuous clozapine therapy. Therefore, clinical vigilance is important, regardless of clozapine treatment duration. Filgrastim can facilitate long-term clozapine therapy in patients with clozapine-induced neutropenia.