• To examine the role of the noradrenergic system in anxiety disorders, 23 patients (nine with generalized anxiety disorders and 14 with panic disorders) were studied for four weeks with clonidine hydrochloride, a predominantly presynaptic noradrenergic agonist, and with placebo. A double-blind crossover design was used. The effect of clonidine was comparable in both anxiety disorders and superior to placebo in patients who tolerated the drug. The conditions of 17% of the patients became worse with the medication. The main effect of clonidine was a decrease of anxiety attacks and "psychic" symptoms. Somatic symptoms were least affected. The complexity of the results may be explained through the postsynaptic effects of clonidine, which in part neutralize its presynaptic noradrenergic effects. It may also indicate disturbances in other neurotransmitter systems that are not affected by clonidine.
Hoehn-Saric R, Merchant AF, Keyser ML, Smith NVK. Effects of Clonidine on Anxiety Disorders. Arch Gen Psychiatry. 1981;38(11):1278-1282. doi:10.1001/archpsyc.1981.01780360094011