Evaluating Treatment of ADHD in Children with Down Syndrome

Inclusion Criteria:

• Stated willingness to comply with all study procedures and availability for theduration of the study.

• Male or female, between the ages of 6.00-17.99 years at the time of consent.

• Able to take oral (liquid) medication.

• English is primary language.

• Meets criteria for ADHD (hyperactivity, inattention, or combined) on the KSADS

• Meets criteria for ADHD (hyperactivity, inattention, or combined) on the Vanderbilt (historically or currently, as indicated by a teacher/professional)

Exclusion Criteria:

• Current use of ADHD stimulant or non-stimulant medication and unwilling todiscontinue for >/= 3 days prior to starting the study.

• Children with psychoses or bipolar disorder based on diagnostic interview with theparent.

• Organic Brain Injury: Children must not have a history of head trauma with loss ofconsciousness, epilepsy, or any other organic disorder that could possibly affectbrain function.

• Specific heart conditions including the following:

1. QTc on baseline ECG>470ms or QTC > 500 in patients with repaired CHD, asdetermined by ECG

2. Brugada pattern, as determined by ECG

3. Baseline heart rate or systolic blood pressure > 2 SD above mean for age asdetermined by medical examination.

4. 2nd or 3rd degree AV block, as determined by ECG

5. History of aborted sudden cardiac death or unexplained syncope as determined bymedical history

6. History of a single ventricle as determined by medical history

7. Valvular regurgitation or stenosis > mild, as determined by ECHO

8. Moderate or greater ventricular dysfunction, as determined by ECHO

9. Pulmonary hypertension, defined as right ventricular pressure >33% systemicpressure or septal position consistent with >mild right ventricularhypertension, as determined by ECHO

10. Use of a pacemaker as determined by medical history

11. Wolff Parkinson White/pre-ventricular excitation, as determined by ECG

12. Atrial, junctional, or ventricular tachyarrhythmia, as determined by ECG

13. Frequent premature ventricular contractions (PVCs) or premature atrialcontractions (PACs), as determined by ECG

14. Abnormal T waves with inversion in V5 and/or V6, bizarre T wave morphology,notched biphasic T waves, or ST segment depression suggesting ischemia orinflammation, as determined by ECG

15. Moderate or larger atrial septal defect, as determined by ECHO

16. Ventricular septal defect > small by ECHO

17. Valvar stenosis > mild by ECHO

18. Aortic root dilation > 2SD above mean by ECHO.

• If participants meet any of the following heart conditions, they must be evaluatedfor the study by a cardiologist before beginning:

1. Right ventricular enlargement/right axis deviation, as determined by ECG

2. Intraventricular conduction delay >120ms in child >12 years old or >100ms inchild <8 years old, as determined by ECG

3. Right or left bundle branch block, as determined by ECG

• Treatment with a monoamine oxidase inhibitor (MAOI) or use of an MAOI within 14days.

• Active titration of non-ADHD, non-MAO psychotropic medication. Stable use ofnon-ADHD, non-MAO psychotropic medication, defined by no dose changes for >/= 4weeks before starting the study medication trial, will be allowed.

• Known hypersensitivity or allergic reactions to methylphenidate or productcomponents such as banana (due to bananas serving as flavoring in the formulation ofthe project's study interventions - Quillivant XR and the placebo).

• Severe Obstructive Sleep Apnea (OSA) as rated by McGill index of 4

• Pregnancy. (Since there is limited information regarding the safety of Quillivant XRduring pregnancy, a pregnancy test will be conducted at the medical screen forfemale participants who have commenced the menstrual cycle. If pregnancy isindicated, the participant will be excluded from the study as a precautionarymeasure).