antihypertensive /-hī·pərten″siv/ , 1. pertaining to a substance or procedure that reduces high blood pressure. 2. an antihypertensive agent. Various drugs achieve their antihypertensive effect by depleting tissue stores of catecholamines in peripheral sites, by stimulating pressor receptors in the carotid sinus and heart, by blocking autonomic nerve impulses that constrict blood vessels, by stimulating central inhibitory alpha2 receptors, or by causing vasodilation. Thiazides and other diuretic agents inhibit the reabsorption of sodium in the renal tubules, increasing urinary excretion of sodium and decreasing plasma and extracellular fluid volume, decreasing blood volume. Drugs that act on adrenergic control of blood pressure include beta-adrenergic blocking agents, which act at beta-adrenergic receptors in the heart and kidneys to reduce cardiac output and renin secretion; and others that act on alpha-adrenergic mechanisms in the central or sympathetic nervous system to reduce peripheral vascular resistance. Vasodilators act directly on the arterioles to produce the same effect. Other drugs used to treat hypertension are hydrochlorothiazide, angiotensin-converting enzyme inhibitors, nonnitrate vasodilators, calcium channel blockers, and angiotensin receptor blockers. Almost every case of hypertension can be controlled by one of these drugs or a combination of them. The proper combination is determined by the response of the individual. In some cases, several drugs must be tried before the right combination is found. Compare antihypotensive.
