Smoking cigarettes induces a liver enzyme, which more rapidly metabolizes and breaks down many of the antipsychotic medications, clearing the medications from the body and reducing effectiveness. Most notably, the newer antipsychotics impacted include olanzapine, clozapine, and asenapine. The older antipsychotics impacted include chlorpromazine and to some extent fluphenazine, perphenazine, and haloperidol. When a patient is taking one of these antipsychotic medications and smoking cigarettes moderately to heavily, the medication will be quickly broken down, removed from the circulation, and be overall less effective, requiring higher doses for symptom control and possibly creating more side effects. If patients are interested in reducing cigarette smoking, it is important to notify their provider since this may significantly impact how their medication works. There are resources available that can be added to treatment, including both prescription and over-the-counter products.