Considerable evidence suggests that hyperactivity of the sympathetic nervous system is implicated not only in the pathogenesis of essential hypertension but also in several blood pressure-independent complications of essential hypertension. Even with the advent of newer antihypertensive agents, including angiotensin-converting enzyme inhibitors and calcium antagonists, the centrally acting sympatholytics (α2-adrenoceptor agonists) remain a valuable group of medications for the management of hypertension of all grades of severity. Their advantages include efficacy; rarity of contraindication; absence of most metabolic and serious side effects; favorable effects on systemic hemodynamics; lack of true tolerance and infrequency of volume expansion-related pseudotolerance; suitability in the elderly, in isolated systolic hypertension, and in patients with various concomitant conditions, such as diabetes mellitus; ability to reverse left ventricular hypertrophy; and relative low cost. The long duration of action of guanfacine hydrochloride, the most recently marketed agent, and of the transdermal formulation of clonidine is an especially commendable feature. The principal disadvantages of this class of medications are an overlap between the therapeutic dosage and that producing sedation and dry mouth and the potential to cause the discontinuation syndrome and sexual dysfunction.
(Arch Intern Med. 1991;151:1638-1644)