Regular Adderall starts to work more quickly and the effects (and hence, side effects) don’t last as long as those of Adderall XR. The “XR” stands for “extended release.” Some doctors and parents prefer Adderall XR for school age children, because in many cases it can be taken once in the morning and last all day. Ordinary Adderall lasts four to six hours on average, while Adderall XR tends to last far longer – up to 12 hours.
The choice of short-acting versus long-acting ADHD medication depends on many factors.