The magnitude of dopamine transporter (DAT) blockade induced by MPH in this population is similar to what is found in ADHD patients without SUD comorbidity. Significant correlation between MPH dosage and DAT occupation. After 3 weeks on MPH, there was a 52% reduction of dopamine transporter binding at the left and right caudate. Similar decreases were found at the left and right putamenThe estimated MPH dose required to block half of the DAT was 0.25 mg/kg of oral MPH blockade of DAT at the striatum. This evidence concerns the gene SLC6A3 and attention deficit-hyperactivity disorder.