Adrenergic Antagonists — MCQs
Effects of beta blockers on the heart are all of the following except:
Which of the following beta blockers is not considered cardioselective?
A mixed α1 blocker and 5-HT1A receptor agonist, used as an antihypertensive agent, is which of the following?
Which of the following is a second-generation beta blocker?
Which of the following is false about pheochromocytoma?
Which class of antihypertensive drugs is known to cause erectile dysfunction?
Which of the following is not an alpha-blocker?
Mechanism of action of curare-like drugs?
Which sympathomimetic drug is primarily known to increase heart rate?
The drug that causes fall in elderly patients with postural hypotension is:-
Adrenergic Antagonists Indian Medical PG Practice Questions and MCQs
Question 1: Effects of beta blockers on the heart are all of the following except:
- A. Decreases duration of systole (Correct Answer)
- B. Decrease in heart rate
- C. May decrease cardiac output initially.
- D. May precipitate heart failure in acute settings.
Explanation: ***Decreases duration of systole*** - Beta-blockers primarily prolong the **duration of systole** by extending the **ejection time** and slowing ventricular relaxation. - They also increase the **diastolic filling time** by reducing heart rate, impacting overall cardiac cycle duration. *Decrease in heart rate* - Beta-blockers block **beta-1 adrenergic receptors** in the heart, leading to a decrease in **sympathetic stimulation** and thus a reduced heart rate. - This effect is beneficial in conditions like **tachycardia** and **angina**, as it reduces myocardial oxygen demand. *May decrease cardiac output initially.* - By reducing heart rate and contractility, beta-blockers can initially decrease **cardiac output**, especially in patients with pre-existing **ventricular dysfunction**. - This effect is often transient, as chronic use can lead to beneficial remodeling and improved efficiency in some conditions. *May precipitate heart failure in acute settings.* - In patients with acutely decompensated heart failure or severe left ventricular dysfunction, beta-blockers can acutely worsen cardiac function due to their **negative inotropic effects**. - Therefore, beta-blockers are typically initiated cautiously at low doses in stable heart failure patients and are contraindicated in acute decompensation.
Question 2: Which of the following beta blockers is not considered cardioselective?
- A. Atenolol
- B. Esmolol
- C. Metoprolol
- D. Carvedilol (Correct Answer)
Explanation: ***Carvedilol*** - **Carvedilol** is a **non-selective beta-blocker** and also possesses **alpha-1 adrenergic blocking activity**, differentiating it from cardioselective agents. - Its mechanism of action involves blocking both **beta-1** and **beta-2 receptors**, as well as **alpha-1 receptors**, which contributes to its broader therapeutic uses, such as in heart failure. *Metoprolol* - **Metoprolol** is considered a **cardioselective (beta-1 selective) beta-blocker** at lower doses, primarily affecting the heart. - It has a lower propensity to cause **bronchoconstriction** or affect peripheral circulation compared to non-selective agents. *Atenolol* - **Atenolol** is a **cardioselective beta-blocker** that preferentially blocks **beta-1 adrenergic receptors** in the heart. - It is frequently used for conditions where specific **cardiac effects** are desired while minimizing impact on other systems. *Esmolol* - **Esmolol** is an **ultra-short-acting**, **cardioselective beta-blocker** that primarily blocks **beta-1 receptors**. - Its rapid onset and short duration of action make it particularly useful in **acute care settings**, such as perioperative hypertension or supraventricular tachyarrhythmias.
Question 3: A mixed α1 blocker and 5-HT1A receptor agonist, used as an antihypertensive agent, is which of the following?
- A. Trimazosin
- B. Tamsulosin
- C. Doxazosin
- D. Urapidil (Correct Answer)
Explanation: ***Urapidil*** - **Urapidil** acts as a **mixed α1-blocker** and has an additional effect as a **5-HT1A receptor agonist**, which contributes to its antihypertensive properties beyond direct vasodilation. - Its unique dual mechanism sets it apart from other alpha-blockers by also modulating serotonin pathways to reduce blood pressure. *Trimazosin* - **Trimazosin** is a **direct-acting peripheral vasodilator** primarily described as an **alpha-adrenergic blocker**, but it does not possess significant 5-HT1A receptor agonist activity. - It is an older antihypertensive medication not commonly used today, with a primary mechanism focused solely on alpha-blocking. *Tamsulosin* - **Tamsulosin** is a **selective α1A-adrenergic receptor antagonist**, specifically used to treat **benign prostatic hyperplasia (BPH)** symptoms by relaxing smooth muscle in the prostate and bladder neck. - It does not have significant 5-HT1A receptor agonist activity, and its primary use is not for general hypertension management. *Doxazosin* - **Doxazosin** is a **selective α1-adrenergic receptor antagonist** used to treat both **hypertension** and **benign prostatic hyperplasia (BPH)**. - While it effectively blocks alpha-1 receptors to lower blood pressure, it does not exert significant agonistic effects on 5-HT1A receptors.
Question 4: Which of the following is a second-generation beta blocker?
- A. Timolol
- B. Atenolol (Correct Answer)
- C. Nadolol
- D. Propranolol
Explanation: ***Atenolol*** - **Atenolol** is a **second-generation beta blocker** characterized by its **cardioselectivity**, meaning it primarily blocks beta-1 receptors in the heart. - This selectively reduces heart rate and contractility with fewer respiratory side effects compared to non-selective agents. *Propranolol* - **Propranolol** is a **first-generation non-selective beta blocker**, meaning it blocks both beta-1 and beta-2 adrenergic receptors. - Its non-selective action can cause significant bronchoconstriction, making it less suitable for patients with respiratory conditions. *Timolol* - **Timolol** is also a **first-generation non-selective beta blocker** commonly used in ophthalmic preparations for glaucoma. - It blocks both beta-1 and beta-2 receptors and does not possess the cardioselectivity of second-generation agents. *Nadolol* - **Nadolol** is another **first-generation non-selective beta blocker** with a long duration of action due to its extensive plasma half-life. - Like other first-generation agents, it lacks cardioselectivity and blocks both beta-1 and beta-2 receptors.
Question 5: Which of the following is false about pheochromocytoma?
- A. Surgery is the treatment of choice
- B. VMA (vanillylmandelic acid) is a diagnostic test
- C. Propranolol is the preferred drug for hypertension control (Correct Answer)
- D. Catecholamines are a diagnostic test
- E. Most pheochromocytomas are benign
Explanation: ***Propranolol is the preferred drug for hypertension control*** - Propranolol, a **beta-blocker**, is generally contraindicated as monotherapy in pheochromocytoma because blocking beta-receptors unopposed can lead to a **hypertensive crisis** due to unopposed alpha-adrenergic vasoconstriction. - **Alpha-blockers** (e.g., phenoxybenzamine) are the first-line agents for hypertension control, followed by beta-blockers once adequate alpha-blockade is established. *Surgery is the treatment of choice* - **Surgical resection** of the tumor is indeed the definitive treatment for pheochromocytoma once the patient has been appropriately prepared with alpha-blockade. - This approach aims to remove the source of excessive catecholamine production and resolve the associated symptoms. *VMA (vanillylmandelic acid) is a diagnostic test* - **VMA** is a metabolic breakdown product of catecholamines, and its measurement in a **24-hour urine collection** is a long-standing method for diagnosing pheochromocytoma. - Elevated VMA levels indicate overproduction of catecholamines, which is characteristic of the tumor. *Catecholamines are a diagnostic test* - Measuring **plasma free metanephrines** and **24-hour urinary fractionated metanephrines** (which are methylated metabolites of catecholamines) are highly sensitive and specific diagnostic tests for pheochromocytoma. - Elevated levels confirm the excessive secretion of these hormones by the tumor. *Most pheochromocytomas are benign* - Approximately **90% of pheochromocytomas are benign**, with only about 10% being malignant. - The **"rule of 10s"** is a helpful mnemonic: 10% bilateral, 10% extra-adrenal, 10% malignant, 10% familial, and 10% occur in children.
Question 6: Which class of antihypertensive drugs is known to cause erectile dysfunction?
- A. Calcium channel blocker
- B. ACE inhibitors
- C. AT1 receptor antagonists
- D. Beta-blockers (Correct Answer)
Explanation: ***Beta-blockers*** - **Beta-blockers** are the antihypertensive class most commonly associated with **erectile dysfunction** - Mechanism: Reduced cardiac output, decreased peripheral blood flow, central nervous system effects reducing libido, and blockade of β2-mediated vasodilation - **Non-selective beta-blockers** (propranolol, nadolol) have higher incidence of ED compared to selective β1-blockers (metoprolol, atenolol) - Newer vasodilating beta-blockers (nebivolol, carvedilol) have lower risk of sexual dysfunction *Calcium channel blockers* - Generally have **neutral or minimal effect** on erectile function - May even improve ED in some patients due to **vasodilatory properties** - Side effects include peripheral edema and headache, but not sexual dysfunction *ACE inhibitors* - Associated with **lower risk of erectile dysfunction** compared to other antihypertensives - May have neutral or even protective effects on sexual function - Preferred choice for hypertensive patients with existing sexual dysfunction concerns - Common side effects: dry cough and angioedema (not related to sexual function) *AT1 receptor antagonists* - **ARBs have neutral to potentially beneficial effects** on sexual function - Considered an excellent alternative for patients experiencing sexual side effects with other antihypertensive medications - Some studies suggest they may improve erectile function in hypertensive patients
Question 7: Which of the following is not an alpha-blocker?
- A. Atenolol (Correct Answer)
- B. Indoramine
- C. Idazoxan
- D. Prazosin
Explanation: ***Atenolol*** - Atenolol is a **selective beta-1 adrenergic receptor blocker**, primarily used to treat hypertension, angina, and certain arrhythmias. - Its mechanism of action involves **blocking the effects of adrenaline** on the heart, leading to decreased heart rate and blood pressure, rather than affecting alpha receptors. *Indoramine* - Indoramine is an **alpha-1 adrenergic receptor blocker** used historically for hypertension. - It specifically **antagonizes alpha-1 receptors** in vascular smooth muscle, causing vasodilation. *Idazoxan* - Idazoxan is an **alpha-2 adrenergic receptor antagonist**, primarily used in research contexts. - It **blocks presynaptic alpha-2 receptors**, which can lead to an increase in norepinephrine release. *Prazosin* - Prazosin is a well-known **alpha-1 adrenergic receptor blocker** used to treat hypertension and benign prostatic hyperplasia (BPH). - It causes **vasodilation** by relaxing vascular smooth muscle, thus lowering blood pressure.
Question 8: Mechanism of action of curare-like drugs?
- A. Blocks ACh receptors (Correct Answer)
- B. Agonistic with ACh receptors
- C. Inhibits ACh synthesis
- D. Causes persistent depolarization
Explanation: ***Blocks ACh receptors*** - Curare-like drugs are **competitive antagonists** at the **nicotinic acetylcholine receptors (nAChRs)** found at the neuromuscular junction. - By binding to these receptors, they prevent acetylcholine (ACh) from binding and activating the receptors, thereby **inhibiting muscle contraction**. *Inhibits ACh synthesis* - Drugs that inhibit ACh synthesis typically target enzymes like **choline acetyltransferase**. - This mechanism would reduce the amount of ACh available, but curare acts directly at the *receptor level*. *Causes persistent depolarization* - This is the mechanism of action of **depolarizing neuromuscular blockers** like succinylcholine. - They initially activate the receptor, causing a brief depolarization, followed by a sustained depolarization that renders the muscle unresponsive. *Agonistic with ACh receptors* - An agonist binds to and activates a receptor, mimicking the effect of the natural ligand (acetylcholine in this case). - Curare-like drugs are **antagonists**; they bind to the receptor but do not activate it, instead blocking ACh binding.
Question 9: Which sympathomimetic drug is primarily known to increase heart rate?
- A. Isoprenaline (Correct Answer)
- B. Phenylephrine
- C. Noradrenaline
- D. Adrenaline
Explanation: ***Isoprenaline*** - **Isoprenaline** (isoproterenol) is a non-selective beta-adrenergic agonist, with a strong affinity for **β1 and β2 receptors** [1]. - Its activation of **β1 receptors** in the heart leads to a significant increase in **heart rate (positive chronotropy)** and contractility (positive inotropy) [1]. - It is the **most potent chronotropic agent** among sympathomimetics and is primarily known for increasing heart rate [2]. *Phenylephrine* - **Phenylephrine** is a selective **α1 adrenergic agonist** that causes vasoconstriction [4]. - It increases blood pressure but typically causes **reflex bradycardia** (decreased heart rate) due to baroreceptor activation. - Does NOT directly increase heart rate. *Noradrenaline* - **Noradrenaline** (norepinephrine) primarily acts on **α1 receptors** causing vasoconstriction, and to a lesser extent on **β1 receptors** [3]. - While it can stimulate β1 receptors, its predominant effect is to increase **mean arterial pressure** through vasoconstriction, often causing **reflex bradycardia** [3]. *Adrenaline* - **Adrenaline** (epinephrine) acts on **α1, β1, and β2 receptors** [4]. While it does increase heart rate via **β1 receptor** stimulation, it also causes significant **vasoconstriction** (via α1) and **vasodilation** (via β2). - Its cardiovascular effects are more complex and dose-dependent compared to isoprenaline's specific chronotropic action.
Question 10: The drug that causes fall in elderly patients with postural hypotension is:-
- A. Acarbose
- B. Prazosin (Correct Answer)
- C. Nor-adrenaline
- D. Metformin
Explanation: ***Prazosin*** - **Alpha-1 adrenergic blocker** used to treat hypertension and benign prostatic hyperplasia (BPH) - Commonly causes **orthostatic hypotension (postural hypotension)** as a side effect by blocking alpha-1 receptors on vascular smooth muscle, preventing compensatory vasoconstriction upon standing - Leads to **dizziness, lightheadedness, and falls**, especially in elderly patients who have reduced baroreceptor sensitivity - **First-dose phenomenon** is particularly notable, with marked hypotension after the initial dose *Acarbose* - Alpha-glucosidase inhibitor used to treat type 2 diabetes by reducing carbohydrate absorption in the intestine - Primary side effects are **gastrointestinal** (flatulence, diarrhea, abdominal discomfort) - Does not affect blood pressure or cause postural hypotension *Nor-adrenaline (Norepinephrine)* - **Vasopressor** and sympathomimetic agent that causes vasoconstriction through alpha-adrenergic receptor stimulation - **Increases blood pressure** and is used to treat severe hypotension in critical care settings - Would not cause falls due to postural hypotension; rather, it counteracts hypotension *Metformin* - **Biguanide** oral hypoglycemic agent for type 2 diabetes that primarily decreases hepatic glucose production and increases insulin sensitivity - Main side effects include gastrointestinal disturbances and rare lactic acidosis - Not associated with postural hypotension or increased risk of falls
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