ADouble-Blind,Placebo-Controlled Withdrawal Trial of Dexmethylphenidate Hydrochloride in Children with Attention Deficit Hyperactivity Disorder

Objectives: d,l

-threo-methylphenidate HCl (d,l-MPH) is the most common treatment of attention deficit hyperactivity disorder (ADHD). A previous report showed placebo-controlled efficacy for the purified d-isomer (dexmethylphenidate hydrochloride, d-MPH, Focalin^™) with a 2:1 potency compared to dl, and suggested a 6-hour duration of action. This study complements that report by studying the effect of placebo-controlled discontinuation and retesting the duration of action.

Methods:

A 6-week, open-label titration of d-MPH (2.5–10 mg twice-a-day) was followed by a double-blind, placebo-controlled, 2-week withdrawal study of responders.

Results: In the open titration, 82% of the 89 enrolled patients achieved a Clinical Global Impression—Improvement (CGI-I) rating of much or very much improved. Only 5 patients discontinued for adverse events. Seventy-five patients continued into the placebo-controlled discontinuation. For the randomly assigned d-MPH (n = 35) and placebo (n = 40) groups, mean ages, respectively, were 10.1 ± 2.9 and 9.9 ± 2.7 years, 86% and 78% were male, and 70.6% and 80.0% took the ceiling dose of 10 mg twice-daily, respectively. Each group had 80% combinedtype ADHD and 20% inattentive type. By the end of the 2-week, placebo-masked withdrawal, significantly more placebo patients (24 of 39) than d-MPH continuers (6 of 35) relapsed (61.5% versus 17.1%, p = 0.001). Compared to d-MPH continuers, placebo patients deteriorated significantly more in the 2-week period on teacher ratings of the 18 ADHD symptoms rated 0–3 (p = 0.028), the 3 p.m. and 6 p.m. parent ADHD symptom ratings (p = 0.0026 and p = 0.0381, respectively), and clinic (2–3 p.m.) and home (6 p.m.) Math Tests (p = 0.024 and p< 0.0001, respectively). The 6 p.m. scores replicated the significant effect at 6 hours reported in the previous study.

Conclusions:

d-MPH is safe, tolerable, and effective, with a 6-hour duration of effect suggested by the significant difference from placebo at 6 hours on a double-blind discontinuation.