ADHD medication isn’t dosed by age or size like a lot of other medications. They right dose is very individualized, depending on your neurotransmitter functioning, your genetics, and your metabolism.
The long-acting/time-release versions of ADHD stimulant medication build and taper and release medication throughout the day. Short-acting medications give you the entire dose immediately when taken and then wear off much the same. Most people prefer long-acting and it seems to keep a more even level of medication throughout the effective time period.
ADDitude Community Moderator, Parenting ADHD Trainer & Author, Mom to teen w/ ADHD, LDs, and autism