Pharmacology Module I: Sympathetic Depressants

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Questions and Answers

Which class of sympathetic depressants does not selectively block alpha receptors?

Non-Selective Alpha Blockers (correct)

Ganglion Blockers

Selective Alpha1 Blockers

Selective Alpha2 Blockers

Which of the following is a characteristic of Selective Alpha1 Blockers?

Partially agonistic effect

Includes Phentolamine

Used primarily for hypertension (correct)

Block both alpha1 and alpha2 receptors

What is an example of a Non-Selective Alpha Blocker?

Prazosin

Phentolamine (correct)

Tamsulosin

Yohimbine

Which of the following statements about Selective Alpha2 Blockers is correct?

Yohimbine is a well-known example Signup and view all the answers

Which of the following is a primary use of alpha blockers?

Treatment of hypertension Signup and view all the answers

What is a common side effect of Non-Selective Alpha Blockers?

Orthostatic hypotension Signup and view all the answers

Which of the following substances is not classified as a sympathetic depressant?

Acetylcholine Signup and view all the answers

Which of these alpha blockers is used in the treatment of benign prostatic hyperplasia?

Tamsulosin Signup and view all the answers

What is the primary indication for the use of phenoxybenzamine?

Prevention or control of hypertensive episodes of pheochromocytoma Signup and view all the answers

Which mechanism explains the action of prazosin as an antihypertensive agent?

Blockade of phosphodiesterase enzyme Signup and view all the answers

What is a common side effect associated with α1 blocking agents like phenoxybenzamine?

Postural hypotension Signup and view all the answers

Which of the following best describes the action of phenoxybenzamine?

Irreversible non-competitive blocking agent Signup and view all the answers

What adverse effect is commonly associated with the Muscarinic blocking action of drugs like phenoxybenzamine?

Dry mouth Signup and view all the answers

Why is there no reflex tachycardia observed with prazosin treatment?

It blocks phosphodiesterase, increasing cAMP levels Signup and view all the answers

Which condition is a contraindication for the use of α-blockers like phenoxybenzamine?

Conditions where a fall in blood pressure is undesirable Signup and view all the answers

Which of the following is NOT a function of prazosin?

Management of pheochromocytoma Signup and view all the answers

Study Notes

Module I: Sympathetic Depressants I

The module covers sympathetic depressants, specifically focusing on alpha-blockers.
The course material was presented by staff members of the Pharmacology department, Faculty of Medicine, NUB.
The intended learning outcomes include understanding the classification of sympathetic depressants, alpha-blockers, pharmacodynamics, uses, and side effects of alpha-blockers.

Code of Conduct

Students should switch off their mobile phones during the lecture.
Aim to be on time and participate effectively in interactions.
Show mutual respect, appreciate differing viewpoints, and remain focused on the topic.
Follow the established code of conduct.

Content: Classification of Sympathetic Depressants

The content covers different classifications of sympathetic depressants, specifically focusing on alpha-blockers.
Includes selective and non-selective alpha-blockers, including subtypes like Alpha1, Alpha2.
Specific examples of alpha-blockers are mentioned (e.g., Phentolamine, Phenoxybenzamine, Prazosin, Tamsulosin, Doxazosin, Yohimbine).

Mechanism of Action, Indications, and Side Effects for Key Alpha Blockers

Phentolamine (Regitine):*
It's a non-selective alpha (α1 and α2) receptor antagonist.
Administered intravenously (I.V) or intramuscularly (I.M).
It has muscarinic actions (increases gastrointestinal motility and secretions) and anti-histaminic and anti-serotonin activity.
Indications include preventing/controlling hypertensive episodes from pheochromocytoma, diagnosing pheochromocytoma, and treating peripheral vascular disease.
Side effects include hypotension (causing reflex tachycardia, cardiac arrhythmias, and myocardial infarction), gastrointestinal stimulation (leading to abdominal pain, nausea, and peptic ulcer exacerbation), and rarely bronchospasm due to histamine release.
Phenoxybenzamine:*
It is a partially selective alpha (α₁ > α₂ ) antagonist that acts as an irreversible, non-competitive blocking agent.
It has long-acting effects with cumulative effects lasting nearly a week.
Used in the treatment of pheochromocytoma, shock, peripheral vascular disease, and carcinoid tumor.
Side effects include postural hypotension, tachycardia, inhibition of ejaculation, nasal congestion, drowsiness, and sedation (due to H₁ blocking). Also, dry mouth (due to muscarinic blocking) .
Contraindicated in conditions where a fall in blood pressure is undesirable.
Prazosin:*
It's a selective alpha-1 receptor antagonist.
It does not typically cause a reflex tachycardia
It inhibits phosphodiesterase enzyme (PDE) and increases cAMP and cGMP, leading to a stable heart rate (HR).
Used in hypertension, congestive heart failure, and Benign Prostatic Hyperplasia (BPH).
Common side effects include first-dose phenomenon, marked postural hypotension, syncope, dizziness, orthostatic hypotension, failure of ejaculation, and salt & water retention.
Tamsulosin/Doxazosin*
Treatment of benign prostatic hyperplasia.
Tamsulosin is often preferred over Doxazosin for BPH, as it has a more favorable side effect profile.
Yohimbine (Yocon):*
This drug is a selective alpha-2 receptor blocker.
Has a role as aphrodisiac and impotence treatment.
A potential side effect is increasing anxiety.

Revision Questions

Reflex tachycardia may occur with Prazosin (True or False).
Phenoxybenzamine is a competitive antagonist of alpha receptors (True or False).
Beta-blockers can be used alone in the treatment of pheochromocytoma (True or False).

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Description

This quiz focuses on Module I of Pharmacology, covering sympathetic depressants with an emphasis on alpha-blockers. Students will explore the classification, pharmacodynamics, uses, and side effects associated with selective and non-selective alpha-blockers. Understanding these concepts is crucial for effective application in medical practice.