Clozapine-Induced Diarrhea: A Case Report and Mechanistic Overview Publisher



Dastmardi S ; Namazi S
Source: Psychiatry and Clinical Neurosciences Reports Published:2026

Abstract

Background: Clozapine is an atypical antipsychotic that is highly effective in managing treatment-resistant schizophrenia. However, its use is associated with a wide range of adverse effects, including agranulocytosis, seizures, sedation, and gastrointestinal issues such as constipation, and less commonly, diarrhea. While constipation is a well-documented side effect of clozapine, diarrhea induced by the drug remains underreported and poorly understood. Case Presentation: A 46-year-old male patient with treatment-resistant schizophrenia developed severe diarrhea, fever, and weight loss shortly after initiating clozapine at a dose of 100 mg three times daily (300 mg/day). These symptoms persisted until clozapine was discontinued, after which they resolved. When clozapine was reintroduced, the symptoms of diarrhea recurred, confirming that clozapine was the causative agent of the gastrointestinal distress. The patient's clinical condition improved once clozapine was discontinued again, highlighting the potential for severe gastrointestinal adverse effects associated with this medication. Conclusion: Clozapine remains a valuable treatment option for individuals with treatment-resistant schizophrenia, but clinicians should be aware of its potential to cause severe gastrointestinal adverse effects, including diarrhea. Early recognition of these side effects, appropriate diagnostic evaluation, and timely management are essential to ensure patient safety and optimize treatment outcomes. In cases where gastrointestinal symptoms are severe, discontinuation of clozapine may be necessary to resolve the issues and prevent further complications. © 2026 The Author(s). Psychiatry and Clinical Neurosciences Reports published by John Wiley & Sons Australia, Ltd on behalf of Japanese Society of Psychiatry and Neurology.