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

Abstract

Objectives: The study objectives were to 1) 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: 1) self-report, 2) pill count, and 3) the Medication Event Monitoring System (MEMS®). 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 XR 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® measures. Both treatments significantly reduced ADHD symptoms, and efficacy was not significantly different between groups. Adherence was not associated with treatment outcome.