A secondary analysis of a racemic amphetamine classroom trial found sex differences on one behavior scale that were not consistently reflected on other outcomes. The result highlights the importance of what each scale measures.
The analysis reused a dose-optimized crossover trial involving 97 children with ADHD, including 38 girls and 59 boys. It was not a new independent experiment. After open-label treatment, participants underwent double-blind racemic amphetamine and placebo conditions.
Researchers compared the ADHD Rating Scale IV, the SKAMP classroom scale and a math-performance measure. Although all relate to classroom functioning, their items and assessment contexts differ.
Boys had worse SKAMP scores beginning at baseline, while corresponding differences were not consistently present on total ADHD ratings or math outcomes. Both sexes improved with racemic amphetamine relative to placebo.
The authors proposed that SKAMP’s coverage of associated disruptive behaviors could contribute to the contrast. That explanation is an interpretation of scale content and the observed pattern, rather than proof of an intrinsic biological difference in medication response.
The trial was not designed or powered primarily to test sex moderation. The analysis was exploratory, did not correct for multiple testing and involved selected children who completed dose optimization. A nonsignificant subgroup contrast cannot establish exact equality.
Industry funding and exclusion of important comorbidities further define the context. The main lesson is to identify the instrument before describing a demographic difference. A classroom score is not a chemical measure of d- or l-amphetamine exposure and does not establish impairment in a particular person or setting.
Read our analysis of the parent racemic-amphetamine formulation trial.
Gender Effects in the Efficacy of Racemic Amphetamine Sulfate in Children with Attention-Deficit/Hyperactivity Disorder. doi:10.1007/s12325-019-00942-5.