Guanfacine is an alpha-2 agonists approved for the treatment of hyperten- sion, but commonly prescribed for post- traumatic stress disorder. Like clonidine, another alpha-2 agonist, guanfacine is believed to decrease norepinephrine release from noradrenergic neurons during states of heightened arousal. In the first randomized, controlled trial of an alpha-2 agonist for PTSD, guanfacine (average dose 2.4 mg QD) was no more effective at reducing symptoms of PTSD than placebo. In addition, the drug was associated with significantly higher reports of adverse effects, including somnolence, lightheadedness, and dry mouth (Neylan et al., Am J Psychiatry 2006;163:2186-2188).