Katzung - Chapter 10

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Questions and Answers

What condition can β-receptor antagonists potentially treat in musicians?

Performance anxiety (correct)

Sleep apnea

Depression

Chronic fatigue syndrome

What is a major adverse effect of β-receptor antagonist drugs?

Dizziness

Worsening of preexisting asthma (correct)

Increased energy levels

Improved respiratory function

In patients with cirrhosis, what benefit do propranolol and nadolol provide?

Reduction in esophageal variceal bleeding (correct)

Increase in mortality rate

Worsening of liver function

Increase in portal vein pressure

What combination appears more effective in preventing rebleeding from esophageal varices?

Nadolol and isosorbide mononitrate Signup and view all the answers

How should β1-selective drugs be used in patients with reactive airway disease?

Very cautiously Signup and view all the answers

Which compound is closely related to nitrogen mustards?

Phenoxybenzamine Signup and view all the answers

Which of the following drugs is NOT an α-receptor–blocking drug?

Sildenafil Signup and view all the answers

What is a potential risk of β blockade in asthma patients?

Severe exacerbation of asthma Signup and view all the answers

Which structural feature is shared by Tamsulosin and Prazosin?

Presence of a methoxy group Signup and view all the answers

Which compound is used specifically as an intermediate in phenoxybenzamine's activity?

Active (ethyleneimonium) intermediate Signup and view all the answers

Which of the following compounds is directly classified as a selective α1-adrenoceptor blocker?

Prazosin Signup and view all the answers

Phentolamine is primarily used for which of the following purposes?

Managing hypertensive crises Signup and view all the answers

Tamsulosin is primarily indicated for the treatment of which condition?

Benign prostatic hyperplasia Signup and view all the answers

Which of the following characteristics differentiates phenoxybenzamine from other α-blockers?

It has an irreversible binding mechanism. Signup and view all the answers

Which α-receptor antagonist has a shorter duration of action?

Phentolamine Signup and view all the answers

What is the primary action of prazosin in the body?

Selective blockade of α1 receptors Signup and view all the answers

Which receptor type is prazosin least effective at antagonizing?

α2 Signup and view all the answers

What distinguishes phenoxybenzamine from prazosin?

Phenoxybenzamine irreversibly binds to α receptors Signup and view all the answers

What is the typical half-life of terazosin?

9–12 hours Signup and view all the answers

Which medication is primarily used for managing urinary symptoms due to benign prostatic hyperplasia (BPH)?

Terazosin Signup and view all the answers

What major effect does phenoxybenzamine have on catecholamine-induced processes?

Attenuation of vasoconstriction Signup and view all the answers

What is the availability of phenoxybenzamine after oral administration?

50% Signup and view all the answers

How does phenoxybenzamine impact blood pressure in normal supine individuals?

Has relatively little effect Signup and view all the answers

What is the mechanism of action for doxazosin in the management of hypertension?

Reversible α1 antagonism Signup and view all the answers

Which of the following drugs is less selective for α1 receptors compared to prazosin?

Phenoxybenzamine Signup and view all the answers

Which drug among the following is classified as a β-receptor antagonist?

Atenolol Signup and view all the answers

What is the primary function of β-receptor antagonists like Propranolol?

Block beta-adrenergic receptors Signup and view all the answers

Which of the following β-receptor antagonists is known for its selective action?

Nebivolol Signup and view all the answers

Identify the drug that has the structure containing isopropyl and hydroxyl groups.

Propranolol Signup and view all the answers

Which β-receptor antagonist is often used in the treatment of glaucoma?

Timolol Signup and view all the answers

Among the following drugs, which one is a non-selective β-receptor antagonist?

Propranolol Signup and view all the answers

Which of the following is a distinguishing feature of Labetalol compared to other β-receptor antagonists?

Has α-blocking activity Signup and view all the answers

What structural component differentiates Metoprolol from Atenolol?

Presence of a methoxy group Signup and view all the answers

Which β-receptor antagonist is considered to have the least lipid solubility?

Atenolol Signup and view all the answers

Which β-receptor antagonist is commonly associated with exerting vasodilatory effects?

Labetalol Signup and view all the answers

Which beta-receptor antagonist is β1-selective and used for treating glaucoma?

Betaxolol Signup and view all the answers

What effect can beta-receptor antagonists have on patients with obstructive cardiomyopathy?

Worsen pulmonary symptoms Signup and view all the answers

What is a potential disadvantage of beta-receptor antagonists in treating patients after a myocardial infarction?

Variable efficacy among different drugs Signup and view all the answers

Which of the following best describes the action of beta-antagonists in hyperthyroidism?

Blockade of adrenoceptors Signup and view all the answers

Which statement regarding β-receptor antagonists that are partial agonists is true based on current evidence?

They are probably less efficacious for secondary prevention post-myocardial infarction Signup and view all the answers

What potential advantage does Betaxolol have regarding systemic adverse effects?

It is potentially less likely to cause systemic issues due to β1-selectivity Signup and view all the answers

Which of the following effects of β-antagonists might vary between different drugs?

Inhibition of peripheral conversion of thyroxine Signup and view all the answers

What condition is mentioned as being potentially improved by beta-receptor antagonists?

Obstructive cardiomyopathy Signup and view all the answers

What patient symptom might worsen with the use of Betaxolol?

Pulmonary symptoms Signup and view all the answers

What is the primary reason for the benefit of β-antagonists in hyperthyroidism concerning heart function?

They block adrenoceptor-driven heart response Signup and view all the answers

Study Notes

Phenoxybenzamine is a nitrogen mustard analog used as an irreversible antagonist of α-receptors.
Causes irreversible blockade of α receptors with effects lasting from 14 to over 48 hours.
It exhibits some selectivity for α1 receptors but is less selective compared to prazosin.
Covalently binds to receptors and reduces the reuptake of norepinephrine in adrenergic nerve terminals.
Also blocks histamine (H1), acetylcholine, and serotonin receptors.
Prazosin is a selective α1 antagonist effective in managing hypertension, 1000-fold less potent at α2 receptors, leading to less tachycardia.
Prazosin relaxes both arterial and venous smooth muscle and improves urinary symptoms in benign prostatic hyperplasia (BPH).

Metabolism and Pharmacokinetics

Phenoxybenzamine has about 50% bioavailability after oral administration, with a half-life of approximately 3 hours.
Terazosin is another reversible α1-selective antagonist, approved for hypertension and BPH, with a half-life of 9-12 hours.
Doxazosin is effective in treating both hypertension and BPH.

β-Receptor Antagonists

β-receptor antagonists (e.g., propranolol, metoprolol) can increase stroke volume in obstructive cardiomyopathy patients.
The efficacy of β-antagonists post-myocardial infarction can vary among drugs within the class.

Hyperthyroidism and β-Antagonists

Excess catecholamines play a harmful role in hyperthyroidism; β-antagonists can alleviate symptoms.
They may block adrenoceptors and inhibit the conversion of thyroxine to triiodothyronine.

Clinical Toxicity of β-Receptor Antagonists

Adverse effects relate to the consequences of β blockade, particularly with nonselective agents.
β2-receptor blockade may exacerbate asthma and other airway issues in susceptible individuals.
Consideration should be given to using hydrophilic β blockers like nadolol or atenolol in patients with CNS side effects from other β blockers.

Miscellaneous Clinical Uses

β-receptor antagonists can decrease portal vein pressure in cirrhosis patients, reducing the risk of variceal bleeding.
Propranolol and nadolol have shown effectiveness in preventing the first episode of bleeding in esophageal varices.
β blockers, especially when combined with treatments like variceal band ligation, can improve outcomes in managing variceal bleeding.

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This quiz covers Phenoxybenzamine, an agent related to nitrogen mustards and its role among autonomic drugs. It highlights its chemical structure and pharmacological significance, providing essential insights for medical students and professionals. Engage with this specialized content to enhance your knowledge in pharmacology.