15 Questions
Which drug is primarily metabolized in the liver through O-demethylation?
Doxazosin
Which alpha-blocker has a lower likelihood of causing reflex tachycardia compared to nonselective alpha-adrenergic antagonists?
Prazosin
Which drug is indicated for treating S&S of benign prostatic hyperplasia (BPH) and has potential side effects of orthostatic hypotension, vertigo, syncope, and ejaculatory dysfunction?
Tamsulosin
Which drug is primarily excreted in the feces and has a terminal elimination half-life of 22 hours?
Doxazosin
Which drug is a long-acting alpha1-adrenergic antagonist and is administered orally for the treatment of benign prostatic hyperplasia (BPH)?
Terazosin
What is the primary effect of α- and β-adrenergic receptor antagonists?
Block the effects of neurotransmitters on their respective adrenergic receptors
What is a common side effect of α-adrenergic blockade?
Orthostatic hypotension
What happens when α2 receptors are agonized presynaptically?
It reduces sympathetic outflow by decreasing neurotransmitter release to the postsynaptic nerve
What effect does drug-induced α-adrenergic blockade have on insulin secretion?
It prevents epinephrine from inhibiting insulin secretion
What is the primary impact of α-adrenergic receptor antagonists on the heart and peripheral blood vessels?
Inhibits the effects of compounds on the heart and peripheral blood vessels
Which type of alpha-adrenergic antagonist is generally not suitable for managing ambulatory essential hypertension due to their side effects?
Nonselective alpha-1 blockers
Which drug is primarily used to treat acute hypertensive emergencies resulting from pheochromocytoma or autonomic nervous system hyperreflexia?
Phentolamine
Which alpha-adrenergic antagonist is the drug of choice for hypertensive crisis from cocaine?
Phentolamine
Which alpha-adrenergic antagonist binds covalently to alpha-adrenergic receptors, resulting in irreversible and insurmountable alpha-receptor blockade?
Phenoxybenzamine
Which condition causes surges of epinephrine and norepinephrine release, leading to labile and unpredictable sympathetic nervous system surges and catecholamine release, resulting in hypertension?
Pheochromocytoma
Study Notes
Alpha-Adrenergic Blockers: Mechanism and Clinical Uses
- Nonselective α-adrenergic antagonists maximize NE's cardiac stimulatory effects, leading to tachycardia without concurrent β-adrenergic blockade.
- Nonselective α-adrenergic antagonists are generally not suitable for managing ambulatory essential hypertension due to their side effects.
- Selective alpha-1 blockers include tamsulosin, terazosin, doxazosin, and prazosin.
- Non-selective alpha blockers include phenoxybenzamine (allosteric inhibitor) and phentolamine (active site inhibitor).
- Alpha-1 blockers are used in conditions such as renal issues and pheochromocytoma, but careful consideration is needed for their systemic effects.
- Phenoxybenzamine and phentolamine are used in pheochromocytoma, with differences in duration of action and mechanism of action.
- Pheochromocytoma causes surges of E and NE release, leading to labile and unpredictable SNS surges and catecholamine release, resulting in hypertension.
- Phentolamine is the drug of choice for hypertensive crisis from cocaine, as beta-blockers are ineffective due to unopposed alpha action.
- Alpha-1 blocker side effects include vasodilation, decreased SVR, and hypotension, with contraindications for cataract surgery and urinary incontinence.
- Phentolamine, prazosin, and yohimbine are competitive and reversible α-adrenergic antagonists, while phenoxybenzamine binds covalently to α-adrenergic receptors, resulting in irreversible and insurmountable α-receptor blockade.
- Phentolamine is primarily used to treat acute hypertensive emergencies, such as those resulting from pheochromocytoma or autonomic nervous system hyperreflexia.
- Phenoxybenzamine is a non-selective alpha-adrenergic antagonist with slow onset, long elimination half-time, and orthostatic hypotension as a prominent side effect.
Test your knowledge of alpha-adrenergic blockers with this quiz. Explore the mechanisms and clinical uses of nonselective and selective alpha-1 blockers, along with their specific applications in conditions such as renal issues, pheochromocytoma, and hypertensive crises. Learn about the differences between phenoxybenzamine and phentolamine and their respective mechanisms of action.
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