Case Report: The clinical implications of clozapine and cigarette smoking

Abstract

INTRODUCTION Cigarette smoking is prevalent among psychiatric patients, with rates several times higher than the general population. As an example, up to 80% of schizophrenic patients smoke cigarettes. Clozapine is extensively metabolized by cytochrome P450 isoenzyme 1A2 and polycyclic aromatic hydrocarbons (PAHs) present in cigarette smoke are thought to induce CYP 1A2. Therefore concurrent smoking with clozapine can potentially lead to decreased clozapine levels and decreased efficacy, while smoking cessation can potentially lead to increased levels and toxicity. Enzyme induction has been reported to result in a 20 to 40% lower mean clozapine concentration in smokers compared to nonsmokers. We present a case of altered serum drug concentrations in association with changes in smoking status in a patient upon admission to a nonsmoking inpatient psychiatric facility.