A Pilot Evaluation of the Safety, Tolerability, Pharmacokinetics, and Effectiveness of Memantine in Pediatric Patients with Attention-Deficit/Hyperactivity Disorder Combined Type

BACKGROUND: Disturbances in N-methyl-D-aspartate (NMDA) receptor activity may play a role in attention-deficit/hyperactivity disorder (ADHD). OBJECTIVE: This study is a preliminary evaluation of the safety, pharmacokinetics, and effectiveness of the NMDA receptor antagonist memantine in pediatric ADHD. METHODS: An open-label, dose-finding, 8-week, trial in outpatients 6-12 years old with ADHD combined type. Memantine oral solution (2 mg/mL) was titrated to 10 mg/day (n = 8) or 20 mg/day (n = 8). Safety data and blood samples for pharmacokinetic analyses were collected. The ADHD Rating Scale-IV (ADHD-IV) and Clinical Global Impression of Severity (CGI-S) scale measured the effectiveness of memantine. RESULTS: There were no discontinuations due to adverse events (AEs), serious AEs, deaths, or suicides. Most AEs were mild and occurred during the first week of treatment. The 20 mg/day memantine dose was associated with a higher rate of completion and larger mean improvement on the ADHD-IV and CGI-S than 10 mg/day memantine. Pharmacokinetic analyses suggest response to memantine may be dose-dependent beyond an initial threshold concentration. CONCLUSIONS: This pilot study suggests that a memantine dose of 20 mg/day may be a safe and possibly effective treatment for pediatric ADHD. Further investigations of memantine in ADHD appear to be warranted.