Adderall XR 20mg This combination medication is used to treat attention deficit hyperactivity disorder – ADHD. It works by changing the amounts of certain natural substances within the brain. Amphetamine/dextroamphetamine belongs to a category of medicine referred to as stimulants. It can help increase your ability to concentrate, stay focused on an activity, and control behavior problems. It may also assist you to arrange your tasks and improve listening skills.