Intuniv takes 4-6 weeks to reach full efficacy. And your child may require dosage adjustments as well. Intuniv is dosed by size/weight though, so your doctor should have an idea of the final target dose from the start.
Here’s more about Intuniv:
ADDitude Community Moderator, Parenting ADHD Trainer & Author, Mom to teen w/ ADHD, LDs, and autism