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19 Cards in this Set
- Front
- Back
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What is the primary effect of an anpha-adrenergic blocking agent?
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Greatly reducing blood pressure. Normal sympa control of the vasculature occurs largely through agonist actions of a-adrenergic receptors, and blockade of these receptors reduces the sympa tone of the blood vessels, resulting in decreased peripheral vascular resistance. **This induces a REFLEX TACHYCARDIA**
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Name the two non-selective ALPHA-RECEPTOR ANTAGONISTS
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Phenoxybenzamine & Phentolamine
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Name the primary alpha-1-selective antagonist
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Prazosin
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Name the primary alpha-2-selective antagonist
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Yohimbine
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Which sympatholytic drugs could be prescribed for hypertension?
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Prazosin (peripheral alpha-1-block, causes vasodilation, lowers TPR), Methyldopa (reduction of sympathetic outflow from CNS through synthesis of false agonist methylnorepinephrine), or Beta-blockers
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what sympatholytic drug would you prescribe for exertional angina?
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beta-blockers
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How about congestive heart failure? WHADDARYA GONNA GO?
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alpha-antagonists (phenoxybenzamine, phentolamine, prazosin) and beta-blockers. huh??
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arrhythmia? (que haces?)
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beta-blockers
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what do you prescribe for pheochromocytoma? (tumor involving chromaffin cells of adrenal medulla? lots of norepi production)
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phenoxybenzamine (peripheral alpha-1 block), and **metyrosine** (inhibition of catecholamine synthesis)
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glaucoma? (puedes hacer una receta por favor?)
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timolol (reduces prod. of aqueous humor by ciliary epithelium, these epithelial cells contain beta-2 receptors, adrenergic input icnrease production and timolol beta-blocks )
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Say you prescribe phenoxybenzamine to someone. what happens if you then administer epinephrine? Why?
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Administration of epi after phenoxybenzamine produces only DEPRESSOR RESPONSES (vasodilation) since alpha-receptors are blocked; this is due to IRREVERSIBLE INHIBITION of phenoxybenzamine. MAximum response to an alpha-agonist is reduced no matter how high the concentration of agonist.
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What is the effect of phenoxybenzamine on the heart?
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stimulatory, like a sympathomimetic. b/c alpha-antagonist causes bp to drop, baroreceptor reflex kicks in and causes tachycardia.
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Name the major difference between phenoxybenzamine and phentolamine
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Phenoxy: irreversible inhibitor. Phentolamine: competitive blocker; also is a prasympa GI tract stimulator and released histamine.
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What are the physiological effects of prazosin?
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Lowers blood pressure. Doesn't increase hr as do other vasodilators. Effective for hypertension.
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Yohimbine has the opposite effects of __________
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clonidine.
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How do you overcome a phentolamine blockade?
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Increase concentration of epi or norepi.
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How do you overcome a phentolamine blockade?
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Increase concentration of epi or norepi.
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Is prazosin free in the blood? Does this affect its effects?
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No, it is bound to plasma proteins, which affects its half-life
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Why is prazosin used more than phenoxybenzamine or phentolamine as an antihypertensive?
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prazosin doesn't increase the heart rate (baroreceptor reflex) as do other vasodilators/alpha-1 antagonists.
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