The PMHNP is treating a 13-year-old boy with attention deficit-hyperactivity disorder and Tourette's syndrome with guanfacine (Intuniv). What is the mechanism of action of guanfacine?

Choice A reason: Norepinephrine reuptake inhibitors increase norepinephrine availability but guanfacine does not inhibit reuptake; its action is through receptor agonism, not reuptake inhibition. Choice B reason: Dopamine reuptake inhibition is the mechanism for some stimulant medications, not for guanfacine, which has a different pharmacologic profile. Choice C reason: Guanfacine is a centrally acting alpha-2A adrenergic receptor agonist. It modulates prefrontal cortex activity, improving attention, working memory, and impulse control. This mechanism also helps reduce tics and hyperactivity in ADHD and Tourette’s syndrome. Choice D reason: Selective serotonin agonists target serotonergic pathways, which is unrelated to guanfacine’s effects on adrenergic receptors and ADHD symptom control.