Evidence about a stimulant must retain the formulation and dose tested. A 2020 trial of low-dose SHP465 mixed amphetamine salts found no significant advantage over placebo, despite positive studies using other regimens.
The actual exposure
The randomized double-blind trial tested oral SHP465 mixed amphetamine salts extended release, 6.25 mg once daily, for four weeks in children aged 6–12 with ADHD. This dose refers to the specified mixed-salts product, not methamphetamine or an interchangeable amount of every amphetamine formulation.
Eighty-nine children were randomized: 45 active treatment and 44 placebo. One placebo participant received no medication. The safety set therefore contained 88 participants, the full analysis set 87 and the completed-study population 83.
The primary result was null
The primary outcome was change in the ADHD Rating Scale, fifth edition, child home version. At week four, the least-squares mean treatment difference was −1.9 points, with a 95% confidence interval from −6.8 to 3.1; p = 0.451.
The clinician global-improvement comparison was also nonsignificant: −0.1 points, 95% confidence interval −0.5 to 0.3. Exploratory age-subgroup analyses did not establish superiority either. The data therefore did not demonstrate efficacy of this regimen under the trial conditions.
What does a null comparison leave open?
Failure to establish a difference is not proof of precisely zero effect. The confidence interval includes both improvement and a difference favoring placebo. The result also cannot establish that higher doses work, even though other studies may address that separate question.
Likewise, a positive study of another dose cannot erase this null trial. Combining the evidence requires retaining dose, population and outcome rather than reporting only the favorable experiments.
Safety was a separate outcome
Treatment-emergent adverse events were reported by 24.4% of active recipients and 16.3% of placebo recipients. Headache and appetite reduction occurred, and vital signs were monitored.
The short study and modest sample do not establish absence of uncommon or long-term adverse effects. “Well tolerated” in the authors’ discussion should not become a claim that low-dose exposure is harmless for every child.
The appropriate historical conclusion
This trial did not establish a four-week symptom benefit from 6.25 mg/day of this extended-release product in its selected pediatric ADHD population. It did not measure drug concentrations, driving or functional impairment from illicit methamphetamine.
The study is useful precisely because it supplies a controlled null finding. It supports careful dose-specific interpretation, not a prescribing instruction to increase treatment or a blanket conclusion about the stimulant class.
Scientific source
Mattingly G, Arnold V, Yan B, Yu M, Robertson B. A Phase 3, Randomized Double-Blind Study of the Efficacy and Safety of Low-Dose SHP465 Mixed Amphetamine Salts Extended-Release in Children with Attention-Deficit/Hyperactivity Disorder. Journal of Child and Adolescent Psychopharmacology. 2020;30:549–557. doi:10.1089/cap.2020.0005. Original commentary on the supplied paper.
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