The principle enzyme involved in the metabolism of clozapine is CYP1A2 with minor contributions from CYP2D6. However, all the subjects will be on a stable dose of clozapine and will continue on the same dosage throughout the study. On the other hand, half the number of subjects will be randomized to augmentation with atomoxetine and since atomoxetine is predominantly metabolized by CYP2D6 with contributions from CYP2C19, we will focus on genetic variations for CYP2D6 and CYP2C19.