 - Received, within 21 days before day 1 of the dose titration phase, therapy with medications that are predominantly metabolized by the enzyme CYP2D6 and have a narrow therapeutic index e.g., flecainide, vinblastine, thioridazine, and most tricyclic antidepressants. The tricyclic antidepressant amitriptyline is permitted. - Experienced a myocardial infarction within 3 months prior to day 1 