Peculiar Paliperidone – A Case of Neutropenia Despite Previous Uneventful Use of a Similar Antipsychotic

Schizophrenia is commonly treated with antipsychotic medications. Among the atypical antipsychotics, routine full blood count investigations are only recommended with the use of clozapine, due to a known risk of agranulocytosis. The objective of this index case is to present a patient who experienced leukopenia and neutropenia with the use of injectable paliperidone, despite previous successful treatment with risperidone. Paliperidone is the metabolite of risperidone and similar in structure. A patient with schizophrenia was treated with oral risperidone for 5 years, without adverse events. He was then given depot paliperidone for better compliance. In the subsequent months of follow-up, he was observed to have leukopenia and neutropenia despite only switching from oral to injectable therapy. Lithium carbonate was used to treat his hematological side effects. Treatment with antipsychotic medications can potentially lead to adverse outcomes, such as leukopenia and neutropenia. Apart from clozapine, routine screening of hematological profiles is not performed. Although hematological side effects from other antipsychotics are rare, they represent serious consequences. As such, there may be value in full blood count monitoring when switching to a new oral antipsychotic, or when switching from oral to injectable antipsychotic therapy. [ Psychiatr Ann . 2022;52(7):302–304.]