Guanfacine extended release adjunctive to a psychostimulant in the treatment of comorbid oppositional symptoms in children and adolescents with attention-deficit/hyperactivity disorder

Objective: The purpose of this study was to assess the effect of guanfacine extended release (GXR) adjunctive to a psychostimulant on oppositional symptoms in children and adolescents with attention-deficit/hyperactivity disorder (ADHD). Methods: A multicenter, double-blind, placebo-controlled dose-optimization study of GXR (1-4 mg/d) or placebo administered morning (a.m.) or evening (p.m.) adjunctive to psychostimulant was conducted in subjects ages 6-17 with suboptimal response to psychostimulant alone. Suboptimal response was defined as treatment with a stable dose of psychostimulant for ≥4 weeks with ADHD Rating Scale IV total score ≥24 and Clinical Global Impressions-Severity of Illness score ≥3, as well as investigator opinion. Primary efficacy and safety results have been reported previously. Secondary efficacy measures included the oppositional subscale of the Conners' Parent Rating Scale-Revised: Long Form (CPRS-R:L); these are reported herein. Results: Significant reductions from baseline to the final on-treatment assessment on the oppositional subscale of the CPRS-R:L were seen with GXR plus psychostimulant compared with placebo plus psychostimulant, both in the overall study population (placebo-adjusted least squares [LS] mean change from baseline to the final on-treatment assessment: GXR a.m.+psychostimulant, -2.4, p=0.001; GXR p.m.+psychostimulant, -2.2, p=0.003) as well as in the subgroup of subjects with significant baseline oppositional symptoms (GXR a.m.+psychostimulant, -3.6, p=0.001; GXR p.m.+psychostimulant, -2.7, p=0.013). Treatment-emergent adverse events were reported by 77.3%, 76.3%, and 63.4% of subjects in the GXR a.m., GXR p.m., and placebo groups, respectively, in the overall study population. Conclusions: GXR adjunctive to a psychostimulant significantly reduced oppositional symptoms compared with placebo plus a psychostimulant in subjects with ADHD and a suboptimal response to psychostimulant alone.