definition of Strattera (atomoxetine hydrochloride): This medication may be prescribed off-label for people with autism to help with hyperactivity, obsessions, and other behavior problems. Strattera® is usually prescribed for the treatment of attention-deficit/hyperactivity disorder (ADHD). Strattera® works by changing the ways some neurons are turned on and off. One possible serious side effect is increased risk of suicidal thinking and behavior in children, adolescents, and young adults. The risk of this side effect needs to be weighed carefully with the clinical need. Families should be aware of the need for close observation of the child or adolescent taking this medication, and maintain communication with the doctor who prescribed it.