Effectiveness and Duration of Effect of Open Treatment in Attention Deficit Hyperactivity Disorder (ADHD) Patients Treated With Lisdexamfetamine Dimesylate(Vyvanse)

Inclusion Criteria: 1. At the time of consent, are between the ages of 18-55, inclusive. 2. Meet DSM-IV criteria for ADHD as assessed by the Adult ADHD Clinician Diagnostic Scale (ACDS) v1.2. 3. Female participants of childbearing potential must test negative for pregnancy at the time of enrollment based on a urine pregnancy test and agree to use a reliable method of birth control during the study. Females of childbearing potential are defined as women not surgically sterilized and are between menarche and 2 years post-menopause. 4. Must have a satisfactory medical assessment with no clinically significant abnormalities as determined by medical history, physical exam, ECG, and clinical laboratory testing. 5. Must be able to swallow capsules. 6. Must be able to begin the daily dose of study medication in the morning. 7. Must be off all ADHD therapies for one week (psychostimulants) and three weeks (non-stimulants). 8. In the opinion of the investigator, the subject must understand and be able, willing and likely to fully comply with the study procedures and restrictions. 9. Must have given signed and dated informed consent in accordance with Good Clinical Practice (GCP) Guidelines. Exclusion Criteria: 1. Participants with a positive urine drug result at Screening. 2. Anyone who meets current DSM-IV-TR criteria for alcohol or any non-alcohol substance abuse or dependence disorder (excluding nicotine). 3. Participants with controlled depressive or anxiety disorders may not participate if, in the opinion of the Principal Investigator, their medications will interfere with safety or efficacy assessments. 4. Participants with any concurrent chronic or acute illness or unstable medical condition that could, in the opinion of the study physician, confound the results of safety assessments, increase risk to the subject or lead to difficulty complying with the protocol. 5. Participants with hypertension at screening, indicated by a blood pressure reading of 135/90 and heart rate above 120bmp. 6. Female participants of childbearing potential who test positive for pregnancy at the time of enrollment based on a urine pregnancy test, or who do not agree to use a reliable method of birth control during the study. Females of childbearing potential are defined as women not surgically sterilized and are between menarche and 2 years post-menopause. 7. Participants who work the night shift or another schedule that would preclude beginning the daily dose of study medication in the morning. 8. Participants who in the investigator's opinion meet any of the exclusionary criteria specified on the FDA label of Vyvanse.