A small cognition study described attention-related changes with lisdexamfetamine and immediate-release mixed amphetamine salts, but it did not conduct inferential statistical comparisons. Its findings should not be converted into proof that one formulation was superior.
Martin and colleagues used a double-blind, three-period crossover design in adults with ADHD. Participants received lisdexamfetamine, 50 mg daily; immediate-release mixed amphetamine salts, 20 mg daily; and placebo for seven days each.
Testing extended to 16 hours after dosing. The primary composite, power of attention, combined simple reaction time, choice reaction time and digit-vigilance speed. The analysis included 18 participants, with one withdrawing because of adverse events.
The largest reductions in the attention composite occurred around five hours after dosing. The reported placebo-relative estimates were larger for lisdexamfetamine than for mixed amphetamine salts. Self-reported ADHD scale scores were unchanged relative to placebo at the reported timepoints.
These are descriptive results. The authors explicitly stated that no inferential statistical comparisons were performed. Numerical differences and confidence intervals should therefore be reported in that methodological context, without inventing a significant head-to-head superiority test.
The two regimens were different formulations at selected doses. The experiment did not establish milligram equivalence or characterize every possible dose-response curve. Sampling through 16 hours also does not establish a precise onset or offset outside the observed measurements.
Participants were generally healthy apart from ADHD. The authors cautioned that medically ill patients and those with substantial psychiatric comorbidity were not characterized.
Reaction-time components provide one view of attention. They do not capture every cognitive demand, real-world productivity or driving performance.
The pilot is useful for examining measurement sensitivity and the time course of observed effects. It does not make a positive amphetamine result evidence of either universal enhancement or impairment.
Related reading: Lisdexamfetamine and a simulated workplace task.