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Questions and Answers
Which type of β-blockers are specifically indicated for hypertensive patients with impaired pulmonary function?
What is a common side effect associated with the use of β-blockers?
Which drug is specifically used for pregnancy-induced hypertension?
What is the effect of non-selective β-blockers on lipid levels?
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What is the mechanism of action for phenoxybenzamine?
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What pharmacological activity do Acebutolol and Pindolol exhibit?
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Which β-blocker primarily affects patients with bradycardia?
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Which of the following drugs can be used to treat benign prostatic hyperplasia?
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Which of the following is a consequence of using β-blockers in diabetic patients?
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What condition is phenoxybenzamine primarily used to treat?
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Reserpine impacts the adrenergic system by blocking what key process?
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Which β-blocker has the shortest half-life?
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What is a common adverse effect of α-adrenergic blockers?
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Which β-blocker has been associated with sedation and depression as side effects?
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Which drug is primarily used in treating stable chronic heart failure?
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What condition should be monitored closely when using β-blockers?
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Which of the following drugs selectively blocks β1 receptors?
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What is the clinical effect of α1 receptor antagonists?
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Which drug is indicated for the treatment of acute glaucoma?
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Which effect is NOT associated with β-blockade?
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Study Notes
α-Adrenergic Receptor Antagonists
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Phenoxybenzamine is a noncompetitive blocker of α1 and α2 receptors.
- Used to treat sweating, hypertension of pheochromocytoma, Raynaud disease, and frostbite.
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Phentolamine is a competitive blocker of α1 and α2 receptors.
- Used to treat hypertension.
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Prazosin, Terazosin, and Doxazosin are selective, competitive blockers of the α1 receptor.
- Decrease peripheral vascular resistance and lower blood pressure by relaxing arterial and venous smooth muscle.
- Used to treat hypertension and benign prostatic hyperplasia.
- Tamsulosin, Alfuzosin, and Silodosin are selective α1 antagonists used to treat benign prostatic hyperplasia.
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Yohimbine is a competitive α2 blocker.
- Historically used as a sexual stimulant and to treat erectile dysfunction.
Clinical Uses
- Pheochromocytoma: Phenoxybenzamine is administered preoperatively to control hypertension.
- Hypertensive emergencies: α-adrenergic receptor antagonists can be used in management.
- Benign prostatic hyperplasia: Prazosin, Terazosin, Doxazosin, Tamsulosin, Alfuzosin, and Silodosin are used.
- Raynaud disease and frostbite: α-adrenergic receptor antagonists are used for treatment.
β-Adrenergic Receptor Antagonists
- Propranolol blocks both β1 and β2 receptors.
- Esmolol has the shortest half-life (10 minutes).
- Nadolol and Nebivolol have the longest half-lives (10-30 hours).
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Main effects:
- Decrease heart rate and contractility
- Decrease renin release
- Bronchoconstriction (β2 blockade)
- Reduce blood pressure
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Other effects:
- Decreased glycogenolysis and glucagon secretion.
- Attenuate the normal physiologic response to hypoglycemia, leading to pronounced hypoglycemia after insulin injection in β-blocker users.
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Clinical uses:
- Systemic and portal hypertension
- Angina
- Cardiac arrhythmias
- Myocardial infarction
- Heart failure
- Hyperthyroidism
- Glaucoma
- Prophylaxis of migraine
- Performance anxiety
- Nadolol and Timolol: block both β1 and β2 adrenoceptors.
- Timolol: reduces aqueous humor production in the eye and is used topically to treat chronic open-angle glaucoma.
- Pilocarpine (a muscarinic agonist) is used for acute glaucoma.
Selective β1 antagonists
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Acebutolol, Atenolol, Betaxolol, Bisoprolol, Esmolol, Metoprolol, and Nebivolol are selective β1 antagonists.
- Used in hypertensive patients with impaired pulmonary function.
- First-line therapy for chronic stable angina.
- Should be avoided in asthmatic patients.
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Acebutolol and Pindolol have partial agonist activity on β1 and β2 receptors (intrinsic sympathomimetic activity).
- Used to treat hypertension with bradycardia.
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Labetalol and Carvedilol are non-selective antagonists of both α and β adrenoceptors.
- Labetalol is used to treat pregnancy-induced hypertension.
- Carvedilol is used to treat stable chronic heart failure.
Side effects
- Bradycardia
- Sedation and depression (nadolol, atenolol)
- Hypoglycemia in diabetic patients
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Other:
- Bronchospasm (β2 blockade)
- Fatigue
- Dry mouth
- Cold extremities
- Erectile dysfunction
- Gastrointestinal disturbances
- Sleep disturbances
Additional information
- Nonselective β-blockers increase triglycerides and reduce high-density lipoprotein ("good" cholesterol).
- These effects are less pronounced with β1-antagonists such as metoprolol.
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Reserpine is a plant alkaloid that blocks the transport of biogenic amines (norepinephrine, dopamine, and serotonin) from the cytoplasm into storage vesicles in the adrenergic nerve terminals, causing depletion of these amines.
- Used to manage hypertension and agitated psychotic states, such as schizophrenia.
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Description
Explore the uses and classifications of α-adrenergic receptor antagonists, including Phenoxybenzamine, Phentolamine, and others. Understand their clinical applications in treating conditions such as hypertension and benign prostatic hyperplasia. This quiz will test your knowledge of these important pharmacological agents.
