Zuclopenthixol and clozapine-induced neutropenia

We highlight a case of zuclopenthixol-induced neutropenia, a rarely reported adverse effect (AE), and subsequent susceptibility to clozapine-induced neutropenia. Neutropenia is an uncommon but clinically significant haematological AE associated with several psychotropic agents, most notably clozapine.We describe a man in his 30s with treatment-resistant schizophrenia who developed medication-induced neutropenia during treatment with both zuclopenthixol and clozapine. Baseline absolute neutrophil count (ANC) was normal (3.16×10⁹/L). During oral zuclopenthixol therapy, the patient developed neutropenia (1.29×10⁹/L) and eosinophilia. ANC normalised following drug discontinuation.Clozapine was subsequently initiated with a cautious titration; however, neutropenia reoccurred (1.31×10⁹/L), with a persistently reduced ANC for 15 days after cessation. Investigations excluded infective, autoimmune, nutritional and primary haematological causes.The patient was subsequently established on amisulpride and lithium, with recovery of ANC. This case highlights the potential susceptibility to antipsychotic-induced neutropenia and the consideration of lithium for augmentation of ANC in future therapy.