Increased prefrontal hemodynamic change after atomoxetine administration in pediatric attention‐deficit/hyperactivity disorder as measured by near‐infrared spectroscopy

Aim Atomoxetine, approved in Japan for the treatment of pediatric attention‐deficit/hyperactivity disorder (ADHD) in April 2009, is a nonstimulant that is thought to act presynaptically via the inhibition of norepinephrine reuptake. Near‐infrared spectroscopy is a non‐invasive optical tool that can be used to study oxygenation and hemodynamic changes in the cerebral cortex. The present study examined the effects of a clinical dose of atomoxetine on changes in prefrontal hemodynamic activity in children with ADHD, as measured by near‐infrared spectroscopy using the Stroop Color–Word Task. Methods Ten children with ADHD participated in the present study. We used 24‐channel near‐infrared spectroscopy to measure the relative concentrations of oxyhemoglobin in the frontal lobes of participants in the drug‐naïve condition and those who had received atomoxetine for 8 weeks. Measurements were conducted every 0.1 s during the Stroop Color–Word Task. We used the ADHD Rating Scale‐IV‐Japanese version (Home Version) to evaluate ADHD symptoms. Results We found a significant decrease in ADHD Rating Scale‐IV‐Japanese version scores, from 30.7 to 22.6 (P = 0.003). During the Stroop Color–Word Task, we found significantly higher levels of oxyhemoglobin changes in the prefrontal cortex of participants in the atomoxetine condition compared with those in the drug‐naïve condition. Conclusions This increase in oxyhemoglobin changes might indicate an intensified prefrontal hemodynamic response induced by atomoxetine. Near‐infrared spectroscopy is a sensitive tool for measuring the pharmacological effects of atomoxetine in children with ADHD.