No use of anticonvulsants, psychostimulants, centrally acting anticholinergics and agents known to inhibit or be metabolized by CYP 3A4 (e.g., erythromycin, chlarythromycin, troleandomycin, fluconazole, miconazole, ketoconazole, itraconazole and grapefruit juice) within 2 weeks prior to enrollment.