Heavy smoking, reduced olanzapine levels, and treatment effects: A case report

A 30-year-old schizophrenic male patient, a heavy smoker, was successfully treated with olanzapine 15 mg/d during hospitalization. His cigarette consumption increased rapidly from 12 to 80 cigarettes per day following his discharge. Ten days later, his delusion of persecution, levels of hostility, and aggressive behavior worsened, while the plasma levels of olanzapine concurrently decreased. Based on our observations of this case, we suggest that the reduced levels of plasma olanzapine and exacerbated clinical symptoms are closely related to the increased consumption of cigarettes. A possible explanation would be that heavy smoking induced cytochrome P4501A2, the major enzyme involved in olanzapine metabolism. Therefore, patients who smoke should be closely monitored for their cigarette consumption when the dosage of olanzapine is adjusted.