Cardiovascular Drugs Practice Questions

Q: Mephenteramine can be used in hypovolemic shock, although intravenous fluid supplementation is primary treatment. It acts by:

All of the above. **Explanation:** Mephentermine is a **mixed-acting sympathomimetic** amine. It acts both directly by stimulating adrenergic receptors and indirectly by releasing endogenous norepinephrine from nerve endings. Its pharmacological profile makes it a potent cardiovascular stimulant. **Why "All of the above" is correct:** Mephentermine acts on both **$\alpha$ and $\beta$ receptors**, leading to a multi-faceted hemodynamic response: 1. **Increasing Cardiac Output (Option A):** Through its $\beta_1$-agonist action, it exerts positive inotropic (increased force) and chronotropic (increased rate) effects, thereby increasing the total cardiac output. 2. **Increasing Systolic Blood Pressure (Option B):** The increase in cardiac output directly elevates the systolic blood pressure (SBP). 3. **Increasing Diastolic Blood Pressure (Option C):** Through its $\alpha$-agonist action, it causes peripheral vasoconstriction, which increases systemic vascular resistance (SVR), leading to a rise in diastolic blood pressure (DBP). **Why individual options are insufficient:** While options A, B, and C are individually correct, they only describe a partial effect of the drug. Since Mephentermine simultaneously improves contractility and vascular tone, it raises all three parameters, making "All of the above" the most accurate clinical description of its action. **High-Yield Clinical Pearls for NEET-PG:** * **Primary Use:** It is most commonly used to prevent or treat **hypotension following spinal anesthesia**. * **Hypovolemic Shock:** While it can support BP, it is **never** the first-line treatment; aggressive IV fluid resuscitation remains the priority. * **CNS Effect:** It has mild CNS stimulant properties (similar to amphetamines) but is much less potent. * **Metabolism:** It is not metabolized by MAO; hence, it has a longer duration of action compared to catecholamines.

Q: Long-acting calcium channel blockers act during which phase of the action potential?

Phase 2. **Explanation:** The correct answer is **Phase 2 (Plateau Phase)**. In the cardiac action potential of non-pacemaker cells (ventricular myocytes), **Phase 2** is characterized by a "plateau." This phase occurs due to a delicate balance between the inward movement of **Calcium ions (Ca²⁺)** through **L-type calcium channels** and the outward movement of Potassium ions (K⁺). Calcium channel blockers (CCBs), such as Verapamil, Diltiazem, and Amlodipine, specifically inhibit these L-type channels. By reducing the inward calcium current during this phase, CCBs shorten the plateau duration and decrease cardiac contractility (negative inotropy). **Analysis of Incorrect Options:** * **Phase 0 (Depolarization):** In ventricular cells, this is driven by the rapid influx of **Sodium (Na⁺)** via fast voltage-gated Na⁺ channels. (Note: CCBs do act on Phase 0 in *pacemaker* cells, but standard CCB pharmacology questions refer to the ventricular plateau). * **Phase 1 (Early Repolarization):** This brief phase is caused by the inactivation of Na⁺ channels and the transient outward flow of **K⁺ ions**. * **Phase 3 (Rapid Repolarization):** This phase is dominated by the massive efflux of **K⁺ ions** through delayed rectifier channels, bringing the membrane potential back to resting levels. **Clinical Pearls for NEET-PG:** * **Class IV Antiarrhythmics:** CCBs (Verapamil/Diltiazem) are classified here; they primarily slow conduction through the AV node by affecting the calcium-dependent upstroke in nodal tissue. * **Dihydropyridines (e.g., Amlodipine):** These are "long-acting" and more selective for vascular smooth muscle, used primarily for hypertension. * **Contractility:** Because Phase 2 provides the calcium necessary for **Calcium-Induced Calcium Release (CICR)** from the sarcoplasmic reticulum, CCBs significantly impact the force of contraction.

Q: Which one of the following drugs is most likely to block K+ channels in the heart responsible for the delayed rectifier current?

Amiodarone. **Explanation:** The question tests the classification of antiarrhythmic drugs based on the **Vaughan-Williams classification**. **Why Amiodarone is Correct:** Amiodarone is a **Class III antiarrhythmic agent**. The primary mechanism of Class III drugs is the blockade of **potassium (K+) channels**, specifically the **delayed rectifier current ($I_{Kr}$)** [2]. By blocking these channels during Phase 3 of the cardiac action potential, Amiodarone prolongs the action potential duration (APD) and the effective refractory period (ERP) [2]. While Amiodarone has Class I, II, and IV activities, its K+ channel-blocking effect is its defining Class III characteristic. **Why the Other Options are Incorrect:** * **Encainide (Option B):** This is a **Class IC** agent. Its primary action is the potent blockade of fast sodium (Na+) channels (Phase 0), significantly slowing conduction velocity with minimal effect on the action potential duration [1]. * **Lidocaine (Option C):** This is a **Class IB** agent. It blocks Na+ channels in the inactivated state and actually tends to *shorten* the action potential duration, rather than blocking K+ channels. * **Phenytoin (Option D):** Also classified as a **Class IB** antiarrhythmic, it is primarily used for digitalis-induced arrhythmias. Like lidocaine, it blocks Na+ channels and does not target the delayed rectifier K+ current. **High-Yield NEET-PG Pearls:** * **Amiodarone Side Effects:** Pulmonary fibrosis, hypothyroidism/hyperthyroidism (due to high iodine content), corneal microdeposits, and "blue-gray" skin discoloration. * **ECG Changes:** Class III agents typically cause **QT interval prolongation**, which carries a risk of *Torsades de Pointes* [2] (though this risk is lower with Amiodarone compared to Sotalol). * **Pure Class III:** While Amiodarone is mixed, **Dofetilide and Ibutilide** are considered "pure" K+ channel blockers.

Q: What is the drug of choice for torsades de pointes?

Magnesium sulphate. **Explanation:** **Torsades de Pointes (TdP)** is a specific form of polymorphic ventricular tachycardia characterized by a "twisting of points" around the isoelectric line, typically occurring in the setting of a prolonged QT interval. **Why Magnesium Sulphate (MgSO₄) is the Correct Answer:** Magnesium sulphate is the **drug of choice** for both the treatment and prevention of recurrences of TdP, regardless of the patient's baseline magnesium levels. It works by blocking **L-type calcium channels**, which suppresses the early after-depolarizations (EADs) that trigger the arrhythmia. It also stabilizes the cardiac membrane without significantly shortening the QT interval itself. **Analysis of Incorrect Options:** * **A. Terfenadine:** This is a non-sedating antihistamine that was withdrawn from the market because it actually **causes** TdP by blocking hERG potassium channels (leading to QT prolongation), especially when taken with CYP3A4 inhibitors. * **B. Quinidine:** A Class IA antiarrhythmic known for causing "Quinidine Syncope." It blocks potassium channels, prolongs the QT interval, and is a notorious **precipitant** of TdP. * **C. Isoprenaline:** While it can be used to increase heart rate (overdrive pacing) to shorten the QT interval in bradycardia-dependent TdP, it is a second-line agent and not the initial drug of choice. **NEET-PG High-Yield Pearls:** * **Dose:** 2 grams IV bolus over 1–2 minutes. * **Congenital Long QT Syndromes:** For Jervell and Lange-Nielsen or Romano-Ward syndromes, **Beta-blockers** (like Propranolol) are the mainstay of chronic management, but MgSO₄ remains the acute treatment for TdP episodes. * **Avoid:** Class IA (Quinidine, Procainamide) and Class III (Sotalol, Amiodarone) antiarrhythmics, as they worsen QT prolongation.

Q: Why is glyceryl trinitrate (GTN) administered sublingually?

To avoid first-pass metabolism. Explanation:1. Why Option A is Correct:Glyceryl Trinitrate (GTN) undergoes extensive high first-pass metabolism in the liver (nearly 90-100% extraction ratio) [1, 2]. If taken orally, the drug is absorbed from the GI tract into the portal circulation and metabolized by hepatic enzymes before reaching the systemic circulation, rendering it ineffective [1, 2]. The sublingual route allows the drug to be absorbed directly through the oral mucosa into the systemic venous circulation (via the superior vena cava), bypassing the liver and ensuring high bioavailability [1].2. Why Other Options are Incorrect:Option B: While sublingual administration does provide a rapid onset of action (1–3 minutes) [2], the primary pharmacological reason for choosing this route over the oral route is the avoidance of metabolic degradation [1]. Rapid onset is a clinical benefit, but avoiding first-pass metabolism is the pharmacokinetic necessity.Option C: GTN is not inherently a gastric irritant; the route is chosen for pharmacokinetic stability, not to protect the stomach lining.Option D: Sublingual administration actually increases the risk of systemic side effects (like throbbing headache and hypotension) because it achieves higher plasma concentrations more quickly than oral administration.3. NEET-PG High-Yield Pearls:Drug of Choice: Sublingual GTN is the drug of choice for acute anginal attacks.Storage: GTN is volatile and light-sensitive; it must be stored in tightly closed, dark glass containers.Mechanism: It acts by releasing Nitric Oxide (NO), which increases cGMP, leading to dephosphorylation of myosin light chains and resulting in venodilation (reducing preload).Other drugs with high first-pass metabolism: Propranolol, Lidocaine, Salbutamol, and Morphine.

Q: Cardiac glycosides are obtained from which plant source?

Strophanthus gratus.. **Explanation:** **Cardiac glycosides** (like Digoxin and Ouabain) are naturally occurring compounds used to increase myocardial contractility. They are primarily derived from two plant genera: **Digitalis** (Foxglove) and **Strophanthus** [1], [2]. * **Why Option B is correct:** **Strophanthus gratus** is the primary source of **G-strophanthin**, also known as **Ouabain** [4]. Another species, *Strophanthus kombe*, provides K-strophanthin. These glycosides inhibit the Na+/K+-ATPase pump, leading to an increase in intracellular calcium and improved cardiac output in heart failure [2], [3]. **Analysis of Incorrect Options:** * **A. Rauwolfia serpentina:** Known as Indian Snakeroot, it is the source of **Reserpine**. It was historically used as an antihypertensive and antipsychotic by depleting catecholamines, not as a cardiac glycoside. * **C. Ricinus communis:** This is the source of **Castor oil** (a stimulant laxative) and the potent toxin **Ricin**. It has no therapeutic role in cardiac contractility. * **D. Atropa belladonna:** Known as Deadly Nightshade, it is a source of **Atropine**. While it affects the heart (increasing heart rate by blocking M2 receptors), it is an anticholinergic, not a cardiac glycoside. **High-Yield Clinical Pearls for NEET-PG:** * **Digoxin** is derived from *Digitalis lanata* (Grecian foxglove). * **Digitoxin** is derived from *Digitalis purpurea* (Purple foxglove) [2]. * **Mechanism:** Inhibition of Na+/K+-ATPase → Increased intracellular Na+ → Decreased Na+/Ca2+ exchange → Increased intracellular Ca2+ (**Positive Inotropy**) [3]. * **ECG Changes:** Characterized by the "reverse tick" or "sagging" ST-segment depression (Salvador Dali sign).

Q: Which of the following possesses the highest efficacy to increase HDL cholesterol?

Nicotinic acid. **Explanation:** **Nicotinic Acid (Niacin)** is the correct answer because it is the most potent agent currently available for increasing HDL cholesterol levels. It typically raises HDL by **15% to 35%**. It achieves this by inhibiting the hepatic breakdown of Apolipoprotein A-I (the primary protein component of HDL), thereby increasing its half-life and circulating levels. Additionally, Niacin inhibits the peripheral mobilization of free fatty acids, reducing VLDL and LDL synthesis. **Analysis of Incorrect Options:** * **Gemfibrozil (Fibrates):** While Fibrates are the drugs of choice for reducing **Triglycerides**, their effect on HDL is modest (usually a 10–15% increase), making them less efficacious than Niacin for this specific purpose. * **Atorvastatin (Statins):** Statins are the gold standard for lowering **LDL cholesterol**. Although they do increase HDL, the effect is minimal (5–10%). * **Enoic acid:** This is likely a distractor referring to fatty acids (like Eicosapentaenoic acid/Omega-3). These are primarily used to lower triglycerides and have negligible effects on raising HDL. **NEET-PG High-Yield Pearls:** * **Side Effects of Niacin:** The most common side effect is **cutaneous flushing** (mediated by Prostaglandin D2/E2), which can be minimized by taking **Aspirin** 30 minutes prior. It can also cause hyperuricemia (precipitating gout) and hyperglycemia. * **Mechanism of Fibrates:** They act as **PPAR-α agonists**, increasing the activity of Lipoprotein Lipase (LPL). * **Drug of Choice Summary:** * To lower LDL: Statins. * To lower Triglycerides: Fibrates. * To raise HDL: Niacin.

Q: Nitroglycerine can be administered by all of the following routes except?

Intramuscular. **Explanation:** Nitroglycerine (Glyceryl Trinitrate - GTN) is a potent vasodilator used primarily for angina pectoris. The correct answer is **Intramuscular (C)** because this route is not used clinically for GTN. Intramuscular injections are avoided due to unpredictable absorption rates and the risk of local tissue irritation, especially when more efficient and titratable routes are available. **Analysis of Options:** * **Oral (A):** GTN can be given orally (sustained-release tablets), but it undergoes **extensive first-pass metabolism** in the liver (bioavailability <1%). Therefore, oral doses must be significantly higher than sublingual doses to be effective. * **Sublingual (B):** This is the **route of choice for acute anginal attacks**. It bypasses the liver (avoiding first-pass metabolism), ensuring rapid onset of action (1–3 minutes). * **Intravenous (D):** Used in **emergency settings** such as unstable angina, acute heart failure, or hypertensive emergencies. It allows for precise titration and immediate effect. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** GTN is a prodrug that releases **Nitric Oxide (NO)**, increasing cGMP and causing smooth muscle relaxation (primarily venodilation, reducing preload). * **Storage:** GTN is volatile and light-sensitive; it must be stored in **dark glass containers** with tight metal caps. * **Tolerance:** Continuous use leads to "Nitrate Tolerance" (depletion of free sulfhydryl groups). A **nitrate-free interval** of 8–12 hours (usually at night) is required to restore sensitivity. * **Contraindication:** Never co-administer with **Sildenafil** (PDE-5 inhibitors) as it can cause life-threatening hypotension.

Question 1

Mephenteramine can be used in hypovolemic shock, although intravenous fluid supplementation is primary treatment. It acts by:

Accepted Answer

All of the above

Answer

Increasing cardiac output

Answer

Increasing systolic blood pressure

Answer

Increasing diastolic blood pressure

Question 2

Long-acting calcium channel blockers act during which phase of the action potential?

Accepted Answer

Phase 2

Answer

Phase 0

Answer

Phase 1

Answer

Phase 3

Question 3

Which one of the following drugs is most likely to block K+ channels in the heart responsible for the delayed rectifier current?

Accepted Answer

Amiodarone

Answer

Encainide

Answer

Lidocaine

Answer

Phenytoin

Question 4

A male patient presents with headache, profuse sweating, and palpitations with a blood pressure of 180/120 mm Hg. What is the drug of choice?

Accepted Answer

Labetalol

Answer

Nifedipine

Answer

Prazosin

Answer

Phenoxybenzamine

Question 5

What is the drug of choice for torsades de pointes?

Accepted Answer

Magnesium sulphate

Answer

Terfenadine

Answer

Quinidine

Answer

Isoprenaline

Question 6

Why is glyceryl trinitrate (GTN) administered sublingually?

Accepted Answer

To avoid first-pass metabolism

Answer

For rapid onset of action

Answer

To prevent gastric irritation

Answer

To minimize side effects

Question 7

Cardiac glycosides are obtained from which plant source?

Accepted Answer

Strophanthus gratus.

Answer

Rauwolfia serpentina.

Answer

Ricinus communis.

Answer

Atropa belladonna.

Question 8

Which of the following possesses the highest efficacy to increase HDL cholesterol?

Accepted Answer

Nicotinic acid

Answer

Gemfibrosil

Answer

Enoic acid

Answer

Atorvastatin

Question 9

Nitroglycerine can be administered by all of the following routes except?

Accepted Answer

Intramuscular

Answer

Oral

Answer

Sublingual

Answer

Intravenous

Question 10

Which drug is typically administered in cardiogenic shock?

Accepted Answer

Dopamine

Answer

Phenylephrine

Answer

Atropine

Answer

Digoxin

Cardiovascular Drugs — MCQs

Cardiovascular Drugs — MCQs

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