 5. Subject has been on stable treatment with commercial SPD489 30, 50, or 70mg for a minimum of at least 6 months preceding the Screening Visit with acceptable tolerability.Prior treatment with commercial SPD489 in the 6 months preceding the Screening Visit must be documented by prescription records, prescribing physician notes, or pharmacy records. Those subjects whose primary care physician PCP is someone other than the Principal Investigator PI will be required to provide the above documentation to the site. 