Infection Risk in Schizophrenia Patients Treated with Clozapine
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Reviewed by Dat Tien Nguyen, B.A, ScM.
Translated by Nhi Phuong Quynh Le, B.A |
Posted on September 12th, 2025
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Clozapine is an antipsychotic commonly used to manage schizophrenia. Unintentionally, the medication has an immunomodulatory effect. In vitro study has found that clozapine can reduce neutrophil count, promote interleukin-6 production, and suppress B-cell activity. Usage of the antipsychotic is also associated with a higher incidence of respiratory infection. A study, recently published in the Lancet, was performed to assess the risk of infection associated with clozapine usage.
The population cohort study was conducted in Hong Kong between 2002 and 2023, and it included more than 10 thousand individuals above the age of 18 who had been diagnosed with schizophrenia. Half of the patients were treated with clozapine, and the other was treated with olanzapine, which is a valid comparator because olanzapine is prescribed in lieu of clozapine, when the latter is contraindicated. Additionally, both agents are structurally similar and target similar neurotransmitter signaling pathways.
Analyses found that clozapine is associated with a 25% higher risk of infection than olanzapine, and this heightened risk is significant regardless of age or gender. This risk is true for infection in the gastrointestinal tract, urinary tract, and respiratory tract. The researchers noted that the higher risk of respiratory infection can also be partially explained by the anticholinergic property of clozapine, which reduces the mucosal layer thickness.
The population cohort study was conducted in Hong Kong between 2002 and 2023, and it included more than 10 thousand individuals above the age of 18 who had been diagnosed with schizophrenia. Half of the patients were treated with clozapine, and the other was treated with olanzapine, which is a valid comparator because olanzapine is prescribed in lieu of clozapine, when the latter is contraindicated. Additionally, both agents are structurally similar and target similar neurotransmitter signaling pathways.
Analyses found that clozapine is associated with a 25% higher risk of infection than olanzapine, and this heightened risk is significant regardless of age or gender. This risk is true for infection in the gastrointestinal tract, urinary tract, and respiratory tract. The researchers noted that the higher risk of respiratory infection can also be partially explained by the anticholinergic property of clozapine, which reduces the mucosal layer thickness.