Sympatholytics peripherally acting

Antihypertensive drugs can be divided into eight classes based on the mechanism of action diuretics, )3-adrenoblockers, centrally acting sympatholytics, peripherally acting sympatholytics, calcium channel blockers, myotropic hypotensive drugs, angiotensin-con-verting enzyme inhibitors, and calcium channel activators. 

Central-acting sympatholytics (e.g., clonidine and methyldopa) Peripheral-acting sympatholytics (e.g., guanadrel) p-blockers Thiazides Anticholinergics Antidepressants... 

Adrenergic Neuron Blockers (peripherally acting sympatholytics) Guanethidine monosulfate (Ismelin), reserpine (Serpasil)... 

Drug Therapy of Hypertension Peripherally Acting Sympatholytics... 

There are two types of sympatholytics those with a direct and an indirect mechanism of action. The direct sympatholytics act via the inhibition of adrenoceptors by competing as antagonists with the transmitters for the binding site. The indirect acting drugs, the so-called antisympathotonics, interfere with the central regulation and/or the peripheral mechanisms of sympathetic transmitter release. 

Fig. 29.1. Calcium second messenger mechanism of vascular smooth muscle contraction and relaxation and sites of action of the peripheral and centrally acting sympatholytics and vasodilators. (From Yeh DC, Michel T. Pharmacology of Vascular Tone. In Golan DE, Tashjian A, Armstrong E, et al., eds. Principles of Pharmacology The Pathophysiologic Basis of Drug Therapy. Baltimore Lippincott Williams Wilkins, 2004 317-330 with permission.)...

Sympatholytic syndrome. Blood pressure and pulse rate are both decreased (peripheral alpha blockers may cause hypotension with reflex tachycardia). The pupils are small, often of pinpoint size. Peristalsis is often decreased. (Examples centrally acting alpha-2 agonists [clonidine and methyidopa], opiates, and phenothiazines.)... 

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