Objective: To evaluate lisdexamfetamine dimesylate maintenance of efficacy in adults with attention-deficit/hyperactivity disorder (ADHD).

Method: Adults (aged 18–55 years) who had ADHD meeting DSM-IV-TR criteria, baseline ADHD Rating Scale-IV (ADHD-RS-IV) with adult prompts total scores of< 22 and Clinical Global Impressions-Severity of Illness (CGI-S) ratings of 1, 2, or 3 were enrolled. After previously receiving commercially available lisdexamfetamine dimesylate (30, 50, or 70 mg/d) for≥ 6 months with acceptable tolerability and maintaining response during a 3-week open-label phase at a stable lisdexamfetamine dimesylate dose, the participants entered a 6-week double-blind randomized withdrawal phase on treatment with lisdexamfetamine dimesylate (same dose) or placebo. Data were collected from April 2009 to July 2010. The primary outcome was the proportion of participants having symptom relapse (≥ 50% increase in ADHD-RS-IV score and≥ 2 rating-point increase in CGI-S score).

Results: A total of 116 participants were randomized (lisdexamfetamine dimesylate n= 56; placebo n= 60).