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The following is a summary of ”High burden of Ileus and Pneumonia in Clozapine-treated individuals With Schizophrenia: A Finnish 25-year follow-up register study,” published in the September 2024 issue of Psychiatry by Partanen et al.

Researchers conducted a retrospective study estimating the frequency and impact of clozapine-related adverse drug events (ADEs) based on long-term data. 

They included 2,659 participants from the FinnGen biobank with schizophrenia and clozapine use, followed for up to 25 years. Health events during clozapine use were identified and adjusted for disease severity. The incidence and recurrence of ADE, its impact on discontinuation, deaths, and pharmacogenetics were examined in the study. 

The results showed that the median follow-up after clozapine initiation was 12.7 years. Among 2,157 health events, 27 were linked to clozapine use, falling into 5 disease categories, including gastrointestinal hypomotility, seizures, pneumonia, acute respiratory infections, and tachycardia. Ileus and pneumonia had cumulative incidences of 5.3% and 29.5%, respectively, and were linked to increased mortality (Ileus OR=4.5; Pneumonia OR=2.8). Reduced CYP2C19 and CYP1A2 activities increased pneumonia risk. 

Investigators concluded that clozapine-induced ileus and pneumonia occur more often than previously reported and were linked to higher mortality. 2 CYP genes impact pneumonia risk, highlighting the need for better preventive measures against these conditions.

Source: psychiatryonline.org/doi/10.1176/appi.ajp.20230744