Guanfacine for the Treatment of Attention-Deficit Hyperactivity Disorder: An Updated Systematic Review and Meta-Analysis

Background: Non-stimulant guanfacine is a common second-line medication for attention-deficit hyperactivity disorder (ADHD). Numerous randomized controlled trials (RCTs) have explored the efficacy of guanfacine in ADHD treatment. This meta-analysis combined data from selected RCTs to analyze the efficacy and safety of guanfacine in treating ADHD. Methods: RCTs were identified from published sources through searches in PubMed, Cochrane Library, Web of Science, and Embase (up to February 2022), defining the Clinical Global Impression of Improvement (CGI-I) treatment response score of <=2 as the primary outcome. Subgroup analysis was performed with a bound treatment duration of 10 weeks. Safety was defined by treatment-emergent adverse events (TEAEs). Results: Twelve out of 332 studies with 2653 participants were included. All studies compared guanfacine with placebos. Guanfacine was significantly more effective in treating ADHD (Risk Ratio [RR] 1.78, 95% CI: 1.59-2.01). In the <10 weeks subgroup, the efficacy in the guanfacine group compared with the placebo group was 58.5% versus 29.4%, respectively (RR 1.97, 95% CI: 1.71-2.26). In the >10 weeks subgroup, the efficacy in the guanfacine group compared with the placebo group was 63.6% versus 39.7%, respectively (RR 1.57, 95% CI: 1.37-1.79). Both subgroups lacked heterogeneity (I² = 0), and a funnel plot showed a low publication bias risk. Around 80% of participants in the guanfacine group experienced at least one TEAE, compared with 66.5% in the placebo group (RR 1.23, 95% CI: 1.14-1.32), with low heterogeneity (I² = 46, p = 0.05). The most common TEAEs in the guanfacine group were somnolence (38.6%), headaches (20.5%), and fatigue (15.2%). Conclusions: Guanfacine is safe and effective for treating ADHD, with no serious adverse events. Guanfacine should be considered as an effective treatment option where effectiveness or tolerability of the central nervous system stimulant is of concern. There is stronger evidence of efficacy for children; more clinical studies are needed for adults.