There will be 6 phases in this study: a screening phase of up to 4 weeks, which will include washout if applicable, an enrollment & parent training phase lasting 2-4 weeks, an eligibility phase of up to 2 weeks to determine eligibility for the open-label phase, a 6-week open-label dose titration phase, a 2 week double-blind phase for Aptensio XR® responders, and a two-week follow-up call after study completion or early discontinuation to assess for ongoing adverse events and concomitant medications.