Efficacy and Safety of Guanfacine Extended-Release in the Treatment of Attention-Deficit/Hyperactivity Disorder in Adults

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Abstract
Objective: To assess guanfacine extended-release (GXR) efficacy and safety in adults with attention-deficit/hyperactivity disorder (ADHD). Methods: This phase 3, double-blind, placebo-controlled study (conducted between October 2016 and July 2017) included Japanese patients aged >= 18 years with ADHD (DSM-5). Patients received GXR (n = 101) or placebo (n = 100) titrated from 2 mg/d to 4-6 mg/d (dose-optimization; 5 weeks), followed by 4-6 mg/d (dose-maintenance; 5 weeks), then tapered doses to 2 mg/d (2 weeks). Primary endpoint was change from baseline in total score on the Japanese version of the ADHD-Rating Scale IV with adult prompts (ADHD-RS-IV) at week 10. Other measures were ADHD-RS-IV subscales, Clinical Global Impression-Improvement scale (CGI-I) and Patient Global Impression-Improvement scale (PGI-I) (percentage of patients very much improved/much improved), treatment-emergent adverse event (TEAE) incidences, and TEAEs leading to discontinuation. Results: Compared with placebo, there was statistically significantly greater improvement in ADHD-RS-IV total score reduction with GXR (least squares mean +/- SE: GXR vs placebo, -11.55 +/- 1.10 vs -7.27 +/- 1.07; P=.0005; effect size 0.52). There were significantly greater improvements in GXR for ADHD-RS-IV inattention (-7.39 +/- 0.79 vs -4.89 +/- 0.76; P=.0032) and hyperactivity-impulsivity (-3.84 +/- 0.54 vs -2.10 +/- 0.52; P=.0021) subscale scores, CGI-I scores (48.1% vs 22.6%; P=.0007), and PGI-I scores (25.3% vs 11.8%; P=.0283). More patients in the GXR versus the placebo group reported TEAEs (81.2% vs 62.0%) and discontinued due to TEAEs (19.8% vs 3.0%). The main TEAEs in the GXR group were somnolence, thirst, blood pressure decrease, nasopharyngitis, postural dizziness, and constipation; most TEAEs were mild to moderate in severity. Conclusions: In Japanese adults with ADHD, GXR improved ADHD symptoms without any major safety concerns.