The d-MPH form has been shown to be the active enantiomer of MPH. Studies have shown that the duration of action of d-MPH is longer than that of racemic MPH. Clinical studies of once a day d-MPH has demonstrated efficacy in children, adolescents and adults with ADHD. Understanding the central nervous system pharmacokinetic properties of the SODAS formulation of the longer-acting (d) enantiomer will provide critical knowledge of its mechanism of action.