Attention Deficit Disorder in Childhood

Efficacy and safety of dexmethylphenidate extended-release capsules in children with attention-deficit/hyperactivity disorder

OBJECTIVE

The efficacy and safety of dexmethylphenidate extended release (d-MPH-ER) was compared to placebo in pediatric patients with attention-deficit/hyperactivity disorder (ADHD).

METHOD

This multicenter, randomized, double-blind, placebo-controlled, parallel-group, two-phase study included 97 patients (ages 6-17 years) with DSM-IV-defined ADHD. The study was carried out between 2001 and 2003. After a 2-week evaluation phase, patients were randomized to d-MPH-ER or placebo for 7 weeks. Flexible d-MPH-ER dosing (30 mg/day) was permitted for 5 weeks, then patients remained on their optimal dose during the last 2 study weeks. The primary efficacy measure was change from baseline to final rating in Conners ADHD/DSM-IV Scale-Teacher version (CADS-T) total subscale score. Secondary efficacy variables included changes from baseline to final visit in CADS-T Inattentive and Hyperactive-Impulsive subscale scores, CADS-P DSM-IV total subscale score and Inattentive and Hyperactive-Impulsive subscale scores, Clinical Global Impressions-Improvement (CGI-I) and CGI-Severity (CGI-S) scale scores, and Child Health Questionnaire Parent Form 50 scores.

RESULTS

d-MPH-ER improved CADS-T total scores significantly compared with placebo (p <.001), and 67.3% of d-MPH-ER patients were rated much improved or very much improved on CGI-I at final visit versus 13.3% of placebo patients (p <.001). More patients taking d-MPH-ER (49.1%) than placebo (25.5%) spontaneously reported adverse events suspected as drug related.

CONCLUSIONS

Once-daily d-MPH-ER was more effective than placebo in the treatment of ADHD in children and adolescents.

Burst activity of ventral tegmental dopamine neurons is elicited by sensory stimuli in the awake cat

In light of evidence implicating dopamine in the pathophysiology of attention deficit disorder and schizophrenia, diseases involving attentional or sensory processing abnormalities, it was of interest to determine whether and how dopamine neurons in the ventral tegmental area respond to sensory stimuli. The single-unit responses of ventral tegmental dopamine neurons were recorded in freely-moving cats during the presentation of brief, non-conditioned auditory and visual stimuli. Both auditory and visual stimuli produced neuronal excitation, involving a greater than 5-fold increase in the probability of burst firing followed by a period of burst inhibition. The burst nature of the single-unit response suggests that sensory-induced dopamine release at target sites was disproportionally large relative to the discharge frequency. While characteristics of the dopaminergic sensory response were similar for auditory and visual stimuli, the response latency was longer for visual stimuli. The results demonstrate that dopamine neurons in the ventral tegmental area, the site of origin for mesolimbocortical dopamine neurons, are reliably activated by non-conditioned auditory and visual stimuli.