Drugs that block both alpha- and beta-adrenergic receptors are primarily used to treat cardiac-related conditions. These drugs include amiodarone (Cordarone), carvedilol (Coreg), and labetalol (Trandate).
Adrenergic blocking agents competitively block the effects of norepinephrine at alpha-and beta-receptors throughout the SNS. Subsequently, this results in lower blood pressure, slower pulse rate, and increased renal perfusion with decreased renin levels. Most of these drugs are indicated to treat essential hypertension, alone or in combination with diuretics.
Labetalol is used IV and orally to treat hypertension. It also can be used with diuretics and has been used to treat hypertension associated with pheochromocytoma (tumor of the chromaffin cells of the adrenal medulla, which periodically releases large amounts of norepinephrine and epinephrine into the system) and clonidine withdrawal. Amiodarone, which is available in oral and IV forms, is saved for serious emergencies and only used as an antiarrhythmic. Carvedilol is only available orally and is used to treat hypertension, as well as heart failure (HF) and left ventricular dysfunction after myocardial infarction (MI).
The nonselective adrenergic blocking agents are contraindicated in patients with known hypersensitivity to any component of the drug to avoid potentially serious hypersensitivity reactions; with bradycardia or heart blocks, which could be worsened by the slowed heart rate and conduction; with asthma, which could be exacerbated by the loss of norepinephrine’s effect of bronchodilation; with shock or HF, which could become worse with the loss of the sympathetic reaction; and who are lactating because of the potential adverse effects on neonates.
These drugs should be used with caution in patients with diabetes because the disorder could be aggravated by the blocked sympathetic response and because the usual signs and symptoms of hypoglycemia and hyperglycemia are masked with the SNS blockade. Caution also should be used in patients with bronchospasm, which could progress to respiratory distress due to the loss of norepinephrine’s bronchodilating actions; and in pregnancy because there are no well-defined studies to evaluate the potential risk to the fetus. The drugs should only be used if the benefit to the mother clearly outweighs the potential risk to the fetus.
amiodarone – n. 胺碘酮 Cordarone – n. 可达龙
carvedilol – n. 卡维地洛 Coreg – n. 卡维地洛商品名
labetalol – n. 拉贝洛尔 Trandate – n. 盐酸拉贝洛尔
norepinephrine – n. 去甲肾上腺素
renin – n. 肾素
essential hypertension – 原发性高血压
chromaffin – a. 嗜铬的
bronchodilation – n. 支气管扩张
aggravate – v. 加重，恶化
mask – v. 掩盖，掩饰
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★Test ★
1. Alpha-adrenergic blockers promote vasodilation. The nurse anticipates what expected therapeutic response from the client taking alpha-adrenergic blockers?
A. Increased blood pressure
B. Decreased blood pressure
C. Decreased pulse rate
D. Rapid respiration
2. A nurse is infusing dopamine (Intropin) intravenously. The nurse is aware that infiltration of this medication may lead to tissue necrosis. What is an early sign of intravenous infiltration?
A. Red streak following the course of the vein
B. Swelling at the IV site
C. Warmth at the insertion site
D. Bleeding at the insertion site
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答案 Answer
1. B. Decreased blood pressure Rationale: Vasodilation leads to a decrease in blood pressure. 2. B. Swelling at the IV site Rationale: Swelling could indicate infiltration, along with coolness, tissue pallor, and local pain.
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