It's known that, patients with schizophrenia smoke more tobacco than general population, and that tobacco is a potent inducer of cythocrome P450 isoenzyme 1A2 (CYP 1A2). In addition, clozapine and quetiapine, drugs frequently used in the treatment of schizophrenia, are CYP1A2 substrates. So, tobacco smoking may reduce blood levels of clozapine and quetiapine.

To revisit the influence of changes in tobacco consumption in clozapine and quetiapine side effects.

Case report.

A 48-year-old male diagnosed of schizophrenia following DSM IV-TR criteria. He required five hospital admissions from 2008 to 2013 because of psychotic episodes. Since 2013, he was asymptomathic receiving clozapine, 600 mg/day, and quetiapine, 1200 mg/day. Recently, he came to the emergency service due to sudden extreme sedation, thinking impairment, sialorrhea, and walking disability. The patient denied treatment abuse and his family confirmed this statement. When asked about toxics he referred progressive tobacco reduction in the last 3 months (from 60 to 20 cigarettes/day). Bearing in mind the relationship between clozapine and quetiapine metabolism and tobacco, treatment was slowly reduced until the doses of clozapine 500 mg/day and quetiapine 400 mg/day. One week after admission, side effects disappeared, psychotic symptoms were not detected, and the patient was discharged.

Inquiring about changes in tobacco consumption may be useful when anti-psychotics side effects appear suddenly without an alternative explanation.

The authors have not supplied their declaration of competing interest.