Comparative ADHD study

A study comparing the effects of two extended-release methylphenidate formulations in children with attention deficit hyperactivity disorder (ADHD) during the school day showed that Celltech's once-daily Metadate CD (methylphenidate HCl, USP) extended-release capsules were more effective than Concerta during the morning hours, and that the two treatments were similar in efficacy during the afternoon.

'The results of this study can help physicians choose the optimal therapy for their pediatric patients with ADHD,' said Dr Simon Hatch, director, clinical development, Celltech Americas, and one of the study authors. 'At the doses we compared, Metadate CD was shown to be superior in efficacy to Concerta in the morning hours and similar in efficacy to Concerta in the afternoon hours. Concerta was shown to be superior in efficacy to Metadate CD at 12 hours.'

Both formulations provide an initial dose of immediate-release methylphenidate (Metadate CD delivers 30% of the daily dose as uncoated beads, Concerta delivers 22% by an overcoat). The initial dose is followed by an extended, controlled delivery of methylphenidate, which Metadate CD delivers by polymer-coated beads and Concerta by an osmotic- release oral system. The study objective was to evaluate differences in the pharmacodynamic (PD) profiles of these two formulations across the day.

'Several different formulations of methylphenidate are available to treat ADHD symptoms, so it is important to understand the time course of effect for each formulation in order to prescribe the most appropriate treatment,' added Hatch. 'This study helps physicians do just that. Using the results of this study as a guideline, physicians can more appropriately determine which medication is best for each patient.'

The multisite, double-blind, three-way crossover study was conducted in a laboratory classroom setting, and compared the pharmacodynamic effects of Metadate CD, Concerta and placebo on attention and behavior in 184 children, ages six to 12, with ADHD. Children were stratified to study treatment based on their pre-study requirements for methylphenidate. The treatment groups were: Low (20 mg Metadate CD, 18 mg Concerta), Medium (40 mg Metadate CD, 36 mg Concerta) or High (60 mg Metadate CD, 54 mg Concerta). Each treatment was administered in randomised order once daily in the morning for a one-week period. At the end of each of the three treatment weeks, children attended a laboratory school, where they were rated by trained observers on attention and deportment (SKAMP Deportment and Attention scale) and by a math test for performance (PERMP) over a 12-hour period.

The study confirmed the authors' hypothesis that, with near-equal daily doses, the overall behavioral effects of Metadate CD were greater than those for Concerta across time periods corresponding to a typical school day (averaged over 1.5-7.5 hours postdose). This effect can be attributed mainly to the larger initial dose of immediate release methylphenidate delivered by Metadate CD and, to a lesser extent, to the different release characteristics of the extended-release portion of each treatment which lead to different PK profiles. The authors believe that the study findings can help guide the selection of the most appropriate once-daily stimulant treatment for children with ADHD.