Efficacy of guanfacine extended release in the treatment of combined and inattentive only subtypes of attention-deficit/hyperactivity disorder.

BACKGROUND: Extended-release guanfacine (GXR) is approved for the treatment of attention-deficit/hyperactivity disorder (ADHD) in children and adolescents aged 6-17 years. This post-hoc analysis further examines the effects of GXR on hyperactivity-impulsivity and inattentiveness.

METHOD: Data from two large double-blind placebo-controlled pivotal trials of GXR in the treatment of ADHD were analyzed. Using the pooled population to provide sufficient sample size and associated statistical power, the impact of GXR treatment on core ADHD symptoms was examined by comparing ADHD Rating Scale IV (ADHD-RS-IV) total scores in the overall GXR and placebo groups in subjects with each of the three ADHD subtypes. ADHD-RS-IV Hyperactivity-Impulsivity and Inattentiveness subscale scores in the overall study population by randomized dose group (vs. placebo) were also examined.

RESULTS: The full analysis set included 631 subjects aged 6-17 years (GXR: n=490; placebo: n=141). Among subjects with the predominantly inattentive subtype of ADHD, differences in least squares (LS) mean reductions from baseline in ADHD-RS-IV total scores were significantly greater in GXR-treated subjects (n=127) than in placebo-treated subjects (n=38) at treatment weeks 3 through 5 and end point (p≤0.020). Among subjects with combined type ADHD, differences in LS mean ADHD-RS-IV total score reductions from baseline were significantly greater in the GXR group (n=354) than in the placebo group (n=100) at treatment weeks 1 through 5 and end point (p≤0.011). The dearth of predominantly hyperactive-impulsive type subjects (n=12) precluded analysis of this subgroup. Each randomized GXR dose group in each trial demonstrated significantly greater reductions from baseline in ADHD-RS-IV Hyperactivity-Impulsivity and Inattentiveness subscale scores than did the respective placebo group at end point (p≤0.05 for all).

CONCLUSIONS: The results support the use of GXR in the treatment of core ADHD symptoms as defined in the American Psychiatric Association Diagnostic and Statistical Manual of Mental Disorders, 4th ed., Text Revision, including hyperactivity, impulsivity, and inattention.