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INTRODUCTION

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Hypertension is recognized as a major risk factor for several potentially lethal cardiac conditions, including myocardial infarction and heart failure. Antihypertensive drugs are organized around a clinical indication—the need to treat a disease—rather than a single receptor type. The drugs covered in this unit have a variety of mechanisms of action including diuresis, sympathoplegia, vasodilation, and antagonism of the renin-angiotensin-aldosterone system, and many agents are available in most categories.

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High-Yield Terms to Learn
Baroreceptor reflex Primary autonomic mechanism for blood pressure homeostasis; involves sensory input from carotid sinus and aorta to the vasomotor center and output via the parasympathetic and sympathetic motor nerves
Catecholamine reuptake pump (norepinephrine transporter [NET]) Nerve terminal transporter responsible for recycling norepinephrine after release into the synapse
Catecholamine vesicle pump Storage vesicle transporter that pumps catecholamine from neural cytoplasm into the storage vesicle; also called vesicle monoamine transporter (VMAT)
End-organ damage Vascular damage in heart, kidney, retina, or brain
Essential hypertension Hypertension of unknown etiology; also called primary hypertension
False transmitter Substance, for example, octopamine, stored in vesicles and released into synaptic cleft but lacking the effect of the true transmitter, norepinephrine
Hypertensive emergency (“malignant hypertension”) An accelerated form of severe hypertension associated with rising blood pressure and rapidly progressing damage to vessels and end organs. Often signaled by renal damage, encephalopathy, and retinal hemorrhages or by angina, stroke, or myocardial infarction
Orthostatic hypotension Hypotension on assuming upright posture; postural hypotension
Postganglionic neuron blocker Drug that blocks transmission by an action in the terminals of the postganglionic nerves
Rebound hypertension Elevated blood pressure (usually above pretreatment levels) resulting from loss of antihypertensive drug effect
Reflex tachycardia Tachycardia resulting from lowering of blood pressure; mediated by the baroreceptor reflex
Secondary hypertension Hypertension caused by a diagnosable abnormality, eg, aortic coarctation, renal artery stenosis, adrenal tumor, etc. Compare essential hypertension.
Stepped care Progressive addition of drugs to an antihypertensive regimen, starting with one (usually a diuretic) and adding in stepwise fashion an angiotensin inhibitor, a sympatholytic, and a vasodilator
Sympatholytic, sympathoplegic Drug that reduces effects of the sympathetic nervous system

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Less than 20% of cases of hypertension are due to (“secondary” to) factors that can be clearly defined and corrected. This type of hypertension is associated with pheochromocytoma, coarctation of the aorta, renal vascular disease, adrenal cortical tumors, and a few other rare conditions. Most cases of hypertension are idiopathic, also called “primary” or “essential” hypertension. The strategies for treating idiopathic hypertension are based on the determinants of arterial pressure (see Figure 6–4). These strategies include reductions of blood volume, sympathetic effects, vascular smooth muscle tension, and angiotensin effects. Unfortunately, the baroreceptor reflex and the renin response in primary hypertension are reset to maintain the higher blood pressure. As a result, they respond to a therapeutically lowered blood pressure with compensatory homeostatic responses, which may be significant (Table 11–1). As ...

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