clonidine
n. a drug used for the treatment of hypertension. It functions by direct stimulation of alpha-adrenergic receptors in the brainstem to restrict the flow of impulses in peripheral sympathetic nerves supplying the arteries, thus causing them to relax (widen); most of the other commonly prescribed antihypertensive drugs act as beta blockers or as diuretics. Clonidine has been used as an adjunctive agent in the management of alcohol and opioid withdrawal, as a nonstimulant treatment for attention-deficit/hyperactivity disorder, and in the management of clozapine-induced sialorrhea (i.e., drooling). It has also been tested in patients with bipolar disorder who are resistant to other drug treatments, but with limited effectiveness. U.S. trade name (among others): Catapres.