Medication Adherence and Symptom Reduction in Adults Treated with Mixed Amphetamine Salts in a Randomized Crossover Study

Objectives: The study objectives were to I) evaluate medication adherence for adults with attention-deficit/hyperactivity disorder (ADHD) treated with 3 times daily (TID) mixed amphetamine salts immediate release (MAS IR) versus once-daily (qAM) MAS extended release (MAS XR) in a randomized, crossover study; and 2) to examine the associations between adherence and efficacy for MAS IR and MAS XR. Methods: Sixty-two adults with ADHD were enrolled and 49 completed the study. The treatment condition order (TID-qAM or qAM-TID) was counterbalanced across participants, with an intervening washout period of >= 7 days. Adherence was assessed via 3 measures: I) self-report, 2) pill count, and 3) the Medication Event Monitoring System (MEMS (R)). The primary efficacy measure was the ADHD Rating Scale (ADHD-RS); secondary measures included the Time-Sensitive ADHD Symptom Scale (TASS) and Clinical Global Impressions Severity of Illness (CGI-S) scale. Results: Adherence to treatment as measured by self-report and pill count was not significantly different between MAS XR and MAS IR. Adherence was significantly better for MAS XR than MAS IR for all of the MEMS measures. The mean change in ADHD-RS, TASS, and CGI-S scores at endpoint was significantly improved for both MAS IR and MAS X R and did not differ significantly between groups. There was not a significant adherence by efficacy interaction. Conclusion: Adults with ADHD adhered equally well with MAS IR as with MAS XR when assessed by pill count and self-report, but not by the MEMS (R) measures. Both treatments significantly reduced ADHD symptoms, and efficacy was not significantly different between groups. Adherence was not associated with treatment outcome.