What you describe is often referred to as rebound. It’s common. Some people eat a good amount of protein before rebound time, and drink lots of water and that helps. Others take a low dose of a short-acting medication just before the rebound period to slow the tapering off of the medication. This is a conversation he needs to have with his prescribing doctor.
ADDitude Community Moderator, Parenting ADHD Coach, Podcaster & Author, Mom to teen w/ ADHD, LDs, and autism