Strattera is a non-stimulant medication known as a norepinephrine reuptake inhibitor used for the treatment of attention-deficit/hyperactivity disorder (ADD and ADHD). It is commonly prescribed to both children and adults. Although the FDA has approved the drug, the current FDA-approved Strattera label states “Poor metabolizers of CYP2D6 have a 5–fold higher peak concentration to a given dose of Strattera compared with extensive metabolizers." 
About 7% of Caucasians and 1-2% of African-Americans and Asians are poor metabolizers (PMs) of CYP2D6 metabolized drugs. 
Like many other pharmaceuticals, individual genetics can play a major role in predicting whether an individual will even respond to Strattera for ADHD, and whether that individual's particular forms of these genes predispose him or her to require a higher (or lower) than normal dosage level than otherwise similar individuals to achieve the desired effects.