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).
TCPR’s Take: While we don’t suggest ditching a potential treatment based ona single study, the onus is now on the research community to provide solid evidence that alpha-2 agonists are helpful for PTSD. On the bright side, prazosin, an antihypertensive with a slightly different mechanism of action (alpha-1 blockade) has been shown effective for symptoms of PTSD in controlled trials (Raskind MA, Biol Psychiatry 2006;Oct 25, epub, available online).
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