Chapter 7 Antihypertensive Agents

Publisher Summary A particularly good correlation has been found between blood pressure and a combination of plasma NE levels and reactivity to exogenous NE. An improved prognosis for hypertensive patients may depend on the type of drug used for treatment in addition to good blood pressure control. Thus, the incidence of fatal and non-fatal coronary heart disease is reported to be significantly lower in patients treated with a β-blocker than in a control group. All the β-blockers, now in common clinical use worldwide, seem to be effective in lowering the blood pressure, but the mechanism of their antihypertensive action is still uncertain. A vasodilating action of the α-blockers alprenolol, propranalol, and oxprenolol has been demonstrated but is probably not significant at therapeutically useful doses. The use of α-blockers in the treatment of hypertension has long been in disrepute. However, the discovery of the unique α-blocking actions of prazosin has generated renewed interest in this form of treatment. Saralasin is only effective in lowering the blood pressure directly dependent on the pretreatment plasma renin activity (PRA). This drug may increase pressure in some patients or cause severe hypotension in patients strongly dependent on angiotensin II for blood pressure maintenance. Rebound hypertension occurs in small percentage of patients after sudden cessation of clonidine therapy. A common characteristic of hypertensive patients, regardless of the etiology of their disease, is abnormally high peripheral vascular resistance. Drugs that act directly on peripheral vasculature to decrease resistance are, therefore, logical agents for the treatment of hypertension.