A Randomized, Open-Label Assessment of Response to Various Doses of Atomoxetine in Korean Pediatric Outpatients with Attention-Deficit/Hyperactivity Disorder

OBJECTIVE This multicenter, randomized, open-label, parallel trial aimed to provide a detailed dose-response profile for atomoxetine in Korean pediatric outpatients with attention-deficit/hyperactivity disorder (ADHD). METHODS Male and female outpatients aged 6-18 years with ADHD meeting symptom severity criteria of 1.5 standard deviations above age and gender norms on the ADHD Rating Scale-IV-Parent: Investigator-Administered and Scored (ADHDRS-IV-Parent: Inv), and a Clinical Global Impression-ADHD-Severity score ≥4 were randomized to atomoxetine (mg/kg/day) 0.2 fixed, 0.5 fixed or 0.5 (7 days), 0.8 (7 days) then 1.2 for 28 days. The primary efficacy measure was change in ADHDRS-IV-Parent: Inv total score after 6 weeks of atomoxetine treatment. RESULTS Of 153 randomized patients, 83.7% were male and mean age was 9.8 (SD±2.4) years. The completion rate was 86.9%. A graded dose response was apparent with mean change in ADHDRS-IV-Parent: Inv total scores of -9.6, -12.3 and -14.5 with atomoxetine 0.2, 0.5 and 1.2 mg/kg/day, respectively (p=0.024 - F-test). Moreover, a greater reduction in ADHD symptoms, as assessed by mean change from baseline to endpoint CGI-S and mean CGI-ADHD-Improvement at endpoint, was also observed with increasing atomoxetine dose. More patients receiving atomoxetine 1.2 mg/kg/day reported ≥1 treatment-emergent adverse event/s (58.3%) compared with 0.5 (40.7%; p=0.11) or 0.2 mg/kg/day (29.4%; p=0.005). These were generally mild to moderate. CONCLUSION Atomoxetine was found to be safe and well tolerated at all doses administered in Korean pediatric ADHD patients, and 1.2 mg/kg/day was an efficacious dose in this population.