Aim Research regarding the effect of antipsychotic medications on the risk of upper respiratory infection (URI) progression to pneumonia in patients with schizophrenia is rare. This study investigated the effect of antipsychotic use on the risk of URI progression to pneumonia in patients with schizophrenia. Methods: This cohort study used the Taiwan's Nationwide Psychiatric Inpatient Medical Claims Database. From January 1, 1996 to December 31, 2012, 22,771 patients with schizophrenia were diagnosed as having the first URI episode after their first psychiatric admission and 135 of them developed pneumonia within 30 days. The duration and dosage of antipsychotics were assessed before and after URI. Cox regression with time-dependent model was used to assess the risk of antipsychotic use on the progression of URI to pneumonia. Results: Among first- and second-generation antipsychotics, clozapine was the only medication associated with an increased risk of developing pneumonia before URI (adjusted hazard ratio [aHR] = 2.05, P = .024). Clozapine was also the only drug significantly associated with an increased risk after URI (aHR = 1.92, P = .027). Regarding medication use after URI, the dosage of clozapine was significantly associated with an increased risk based on Cox regression with a time-dependent model (aHR = 1.95, P = .003). Conclusions: The use of clozapine was associated with URI progression to pneumonia in patients with schizophrenia. The dosage of clozapine used in the post-URI period was also associated with an increased risk. Clinicians should consider lowering clozapine dosage in patients with URI to prevent them developing pneumonia.
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