Objectives:Amphetamines are a preferred treatment for attention-deficit/hyperactivity disorder (ADHD), with the dextroamphetamine transdermal system (d-ATS) providing an alternative to oral formulations. A pivotal trial of d-ATS in children and adolescents with ADHD met primary and key secondary endpoints. This analysis reports additional endpoints and safety findings from the pivotal trial and evaluates effect size and number needed to treat (NNT) for d-ATS.Methods:In this study, a 5-week, open-label dose-optimization period (DOP) preceded a 2-week, randomized, crossover double-blind treatment period (DBP). Eligible patients received d-ATS 5 mg during the DOP, with weekly evaluations for increase to 10, 15, and 20 mg (equivalent to labeled doses of 4.5, 9, 13.5, and 18 mg/9 hours, respectively) until reaching and maintaining the optimal dose, which was utilized for the DBP. Secondary endpoints included assessment of Attention-Deficit/Hyperactivity Disorder Rating Scale IV (ADHD-RS-IV), Conners' Parent Rating Scale Revised Short Form (CPRS-R:S), and Clinical Global Impression (CGI) scores. NNT was calculated for ADHD-RS-IV and CGI-Improvement (CGI-I). Safety assessments included treatment-emergent adverse events (TEAEs) and dermal safety.Results:In total, 110 patients entered the DOP, with 106 patients randomized (DBP). During the DBP, the least-squares mean (95% confidence interval) difference for d-ATS versus placebo in ADHD-RS-IV total score was −13.1 (−16.2 to −10.0;p< 0.001), with effect size of 1.1 and NNT of 3 for ADHD-RS-IV remission, ≥30% improvement, and ≥50% improvement. Significant differences between placebo and d-ATS were also observed for CPRS-R:S and CGI-I scales (p< 0.001), with NNT of 2 for CGI-I response. Most TEAEs were mild or moderate, with three leading to study discontinuation in the DOP and none in the DBP. No patients discontinued due to dermal reactions.Conclusions:d-ATS was effective in treating ADHD in children and adolescents, meeting all secondary endpoints, with a large effect size and NNT of 2–3 to achieve a clinically meaningful response. d-ATS was safe and well tolerated, with minimal dermal reactions.Clinical Trial Registration:NCT01711021.