Pharmacological Actions of Alpha Adrenergic Receptors Antagonists

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Questions and Answers

What is the characteristic feature of alpha adrenergic receptor antagonists?

Lowering blood pressure through blocking of the α1-receptors (correct)

Increasing blood pressure through blocking of the α1-receptors

Relaxing smooth muscle in the bladder neck

Enhancing sympathetic control of the bladder

Why are selective α-receptor antagonists like Tamsulosin used?

To relax smooth muscle in the bladder neck and manage benign prostatic hyperplasia (correct)

To lower blood pressure

To decrease resistance to outflow of urine

To enhance sympathetic control of the bladder

Why is Prazocin no longer commonly used as an antihypertensive agent?

It has no effect on blood pressure

It has severe adverse effects

It causes excessive relaxation of smooth muscle in the bladder neck

It is less effective than many other antihypertensive agents (correct)

What is the distinctive pharmacological action of α1A-receptor antagonists like Tamsulosin?

Relaxing smooth muscle in the bladder neck and prostate capsule Signup and view all the answers

What is the main use of Tamsulosin?

Relaxing smooth muscle in the bladder neck and managing benign prostatic hyperplasia (BPH) Signup and view all the answers

Which type of drug is used to prevent the excessive stimulation of α-receptors by endogenous catecholamines released by pheochromocytoma?

Irreversible non-selective α-receptor antagonist Signup and view all the answers

Why are more selective agents on specific α-receptor subtypes more widely used?

Due to their distinctive pharmacological action on the bladder neck with less vascular effect Signup and view all the answers

What is the characteristic adverse reaction of α-receptor antagonists?

Postural (orthostatic) hypotension Signup and view all the answers

Which β-receptor antagonist is a non-selective agent and the prototype of this class of drugs?

Propranolol Signup and view all the answers

What is the therapeutic benefit of β1-receptor blockade in clinical situations such as hypertension and ischemic heart disease?

Reduced peripheral resistance Signup and view all the answers

Which characteristic distinguishes lipid-soluble β-blockers from water-soluble ones?

Hepatic first pass metabolism Signup and view all the answers

Which type of β-receptor antagonist has α-blocking activity?

Carvedilol Signup and view all the answers

What distinguishes short-acting β-blockers from long-acting ones?

Half-life and duration of action Signup and view all the answers

What is the expected adverse effect of non-selective agents blocking both β1 and β2 receptors?

Tachycardia Signup and view all the answers

Why should treatment with α-receptor antagonists be started with lower doses at bedtime and increased gradually to standard doses?

To minimize postural (orthostatic) hypotension Signup and view all the answers

What is the primary therapeutic benefit of non-selective agents with α-blocking activity?

Reduced peripheral resistance and decreased blood pressure Signup and view all the answers

Study Notes

Alpha Adrenergic Receptor Antagonists

Characteristic feature includes selective blockade of alpha adrenergic receptors, leading to vasodilation and reduced blood pressure.
Selective α-receptor antagonists like Tamsulosin are utilized primarily for their effectiveness in treating benign prostatic hyperplasia (BPH) with minimal side effects.

Prazocin Usage

Prazosin is less commonly used as an antihypertensive agent due to adverse effects like first-dose hypotension and the availability of more effective medications.

α1A-Receptor Antagonists

Distinctive pharmacological action of α1A-receptor antagonists, such as Tamsulosin, focuses on smooth muscle relaxation in the prostate and bladder neck, improving urinary flow.

Main Uses and Applications

Tamsulosin's main use is for the management of urinary symptoms associated with benign prostatic hyperplasia (BPH), enhancing quality of life.

Pheochromocytoma Treatment

Drugs that prevent excessive stimulation of α-receptors by catecholamines, such as phenoxybenzamine, are used in the management of pheochromocytoma.

Selectivity in Drug Use

More selective agents targeting specific α-receptor subtypes are preferred due to their improved efficacy and reduced risk of adverse effects.

Adverse Reactions of α-Receptor Antagonists

Characteristic adverse reaction includes orthostatic hypotension, leading to dizziness and fainting upon standing.

Non-Selective β-Receptor Antagonists

Propranolol is a non-selective β-receptor antagonist and serves as the prototype for this class of drugs.

Therapeutic Benefits of β1-Receptor Blockade

β1-receptor blockade is beneficial for controlling heart rate, reducing cardiac workload, and managing hypertension and ischemic heart disease.

Solubility of β-Blockers

Lipid-soluble β-blockers can cross the blood-brain barrier, potentially leading to central nervous system effects, while water-soluble ones are less likely to affect the brain.

β-Receptor Antagonists with α-Blocking Activity

Carvedilol and labetalol are examples of β-receptor antagonists that also possess α-blocking activity.

Duration of Action in β-Blockers

Short-acting β-blockers require more frequent dosing, whereas long-acting β-blockers provide sustained effects and are dosed less frequently.

Adverse Effects of Non-Selective β-Blockers

Blocking both β1 and β2 receptors can lead to respiratory issues such as bronchospasm, especially in susceptible individuals like those with asthma.

Starting Doses for α-Receptor Antagonists

Initiating treatment with lower doses at bedtime and increasing gradually helps mitigate risks of severe hypotension and allows for patient adjustment.

Primary Therapeutic Benefit of Non-Selective Agents

Non-selective agents with α-blocking activity provide comprehensive blood pressure reduction and help in conditions like hypertensive emergencies.

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Description

This quiz covers the pharmacological actions, uses, and adverse effects of alpha adrenergic receptors antagonists, with a focus on their effect on lowering blood pressure through blocking of the α1-receptors. It also discusses why they are less likely to be used for this purpose except in selected cases.