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, such as atomoxetine, increase synaptic norepinephrine but are mechanistically different from guanfacine. Choice B reason: Dopamine reuptake inhibitors affect dopaminergic signaling and are not the primary mechanism of guanfacine. Choice C reason: Guanfacine is a centrally acting alpha-2A adrenergic receptor agonist. It enhances prefrontal cortex regulation by reducing sympathetic outflow, which helps control attention, hyperactivity, and impulsivity in ADHD and can reduce tics in Tourette’s syndrome. Choice D reason: Selective serotonin agonists, such as SSRIs, primarily modulate serotonergic neurotransmission and are not the mechanism of guanfacine.