The Intuniv was likely prescribed to combat medication rebound and symptoms like impulsivity when the stimulant wears off. Definitely talk to the prescribing doctor about this.
Stimulants aren’t prescribed based on size or age. The right dosage depends on an individual’s genetics, metabolism, and neurotransmitter functioning. Learn more about how ADHD medications work here:
ADDitude Community Moderator, Parenting ADHD Trainer & Author, Mom to teen w/ ADHD, LDs, and autism