Respiratory Infections Rather Than Antibiotics May Increase Clozapine Levels: A Critical Review of the Literature

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Sir: Approximately 70% of clozapine metabolism is explained by the cytochrome P450 1A2 (CYP1A2).1 The CYP1A2 can be inhibited by respiratory infections. Decreased theophylline (a CYP1A2 substrate) clearance during upper respiratory infections has been described in asthmatic children2,3 and in adults with chronic bronchitis.4

J Clin Psychiatry 2004;65(8):1144-1145