It could be that he needs a dosage or medication change since it’s not working for him anymore. During the times when it’s wearing off, try to keep him hydrated and have a high protein snack just before. Make sure you’ve planned some calm down time. Don’t ask him to do a non-preferred task during that time unless you absolutely have to.
Penny
ADDitude Community Moderator, Parenting ADHD Trainer & Author, Mom to teen w/ ADHD, LDs, and autism