The primary objective of this study is to evaluate the long-term safety and tolerability of methylphenidate hydrochloride extended-release capsules (Aptensio XR®) in children aged 4-5 years who have been diagnosed with attention-deficit/hyperactivity disorder (ADHD).

Safety and tolerability will be evaluated by assessing treatment-emergent adverse events (TEAEs) blood pressure, pulse, height, weight, electrocardiograms (ECGs), laboratory The primary objective of this study is to evaluate the long-term (12-month) safety and tolerability of Aptensio XR® in children aged 4 to less than 6 years who have been diagnosed with ADHD.

Safety and tolerability will be evaluated by assessing treatment-emergent adverse events (TEAEs) blood pressure, pulse, height, weight, electrocardiograms (ECGs), laboratory values and Columbia Suicide Severity Rating Scale (C-SSRS). Disturbances in sleep (quantity and quality) patterns will also be assessed using the Child Sleep Habits Questionnaire (CSHQ).

Secondary objectives include assessment of long-term efficacy of Aptensio XR®.

Secondary measures include:

• Investigator administered Attention-Deficit/Hyperactivity Disorder Rating Scale Preschool Version (ADHD-RS-IV Preschool Version)
• Clinical Global Impressions-Severity Scale (CGI-S )
• Connors Early Childhood Behavior-Parent Short form [Conners EC BEH-P(S)]

Inclusion Criteria:

• Male and female subjects aged 4 to less than 6 years inclusive at the time consent was given to participate in Prior Studies. New Subjects must be at least 4 years but less than 6 years of age when written consent is given to participate in this trial.