The main target of typical stimulants in the brain is the dopamine transporter (DAT) (Volkow, Wang et al. 1998). We have an exquisitely sensitive methodology to measure DAT occupancy using C-11 altropane and Positron Emission Tomography (PET) (Fischman, Bonab et al. 2001). Our group has previously documented the central nervous system pharmacokinetics of several psychiatric drugs (including methylphenidate) using similar techniques. (Christian, Livni et al. 1996; Fischman, Bonab et al. 1996; Fischman, Alpert et al. 1997; Salazar and Fischman 1999; Fischman, Alpert et al. 2002; Spencer, Biederman et al. 2006).