Cardiovascular Drugs Practice Questions

Q: What is the mechanism of action of sodium nitroprusside?

Increased guanylate cyclase. **Mechanism of Action: Sodium Nitroprusside** **Explanation of the Correct Answer:** Sodium nitroprusside (SNP) is a potent, rapid-acting parenteral vasodilator. Unlike organic nitrates (like nitroglycerin) which require enzymatic bioactivation, SNP is a non-enzymatic nitric oxide (NO) donor. Once in the bloodstream, it spontaneously releases NO, which activates the enzyme **soluble guanylate cyclase**. This leads to an increase in intracellular **cyclic GMP (cGMP)**. Elevated cGMP levels activate protein kinase G, resulting in dephosphorylation of myosin light chains and sequestration of calcium, which causes profound relaxation of both **arteriolar and venous** smooth muscle. **Analysis of Incorrect Options:** * **A. Increased cAMP:** This is the mechanism for drugs like Beta-2 agonists (Salbutamol) or PDE-3 inhibitors (Milrinone), which cause vasodilation via the cAMP pathway, not NO. * **C. Calcium channel blockage:** This describes the mechanism of CCBs (e.g., Amlodipine, Verapamil), which inhibit the entry of calcium into the cell. * **D. K+ channel opener:** Drugs like Minoxidil, Diazoxide, and Nicorandil work by opening ATP-sensitive potassium channels, leading to hyperpolarization and vasodilation. **NEET-PG High-Yield Pearls:** * **Balanced Vasodilator:** SNP acts equally on veins (reducing preload) and arteries (reducing afterload). * **Clinical Use:** Drug of choice for **Hypertensive Emergencies** and controlled hypotension during surgery. * **Toxicity:** Metabolism of SNP releases **cyanide**. Chronic infusion or high doses can lead to cyanide and thiocyanate toxicity. * **Antidote:** Sodium thiosulfate or Hydroxocobalamin (Vitamin B12a) are used to treat SNP-induced cyanide poisoning. * **Light Sensitivity:** SNP is photosensitive; the infusion bottle must be covered with opaque foil.

Q: Which of the following is NOT an arteriolar dilator?

Nitrates. ### Explanation The classification of vasodilators is based on their site of action: pure arteriolar dilators, pure venodilators, or mixed (balanced) vasodilators. **Why Nitrates are the correct answer:** Nitrates (e.g., Nitroglycerin, Isosorbide dinitrate) are primarily **venodilators**. At therapeutic doses, they increase venous capacitance, which decreases venous return to the heart (preload). This reduces myocardial oxygen demand, making them the mainstay for angina. While they can cause arteriolar dilation at very high doses, their predominant clinical effect is on the venous side. **Analysis of Incorrect Options:** * **Hydralazine:** A direct-acting **pure arteriolar dilator**. It acts by increasing cGMP levels and interfering with calcium release. It is commonly used in pregnancy-induced hypertension. * **Minoxidil:** A potent **pure arteriolar dilator**. It works by opening ATP-sensitive $K^+$ channels, leading to hyperpolarization of smooth muscle. It is reserved for refractory hypertension and is known for causing hypertrichosis. * **Nifedipine:** A Dihydropyridine Calcium Channel Blocker (CCB). These agents act specifically on L-type calcium channels in the vascular smooth muscle of **arterioles**, causing significant peripheral vasodilation. **High-Yield Clinical Pearls for NEET-PG:** * **Mixed Vasodilator:** **Sodium Nitroprusside** is the classic example of a balanced vasodilator (acts on both arteries and veins). * **The Reflex Phenomenon:** Pure arteriolar dilators (Hydralazine, Minoxidil) often cause **reflex tachycardia** and **sodium/water retention**. Therefore, they are usually prescribed alongside a $\beta$-blocker and a diuretic. * **Drug of Choice:** Hydralazine is a preferred agent for **Hypertension in Pregnancy**. * **Side Effect:** Minoxidil can cause pericardial effusion; Hydralazine is associated with **Drug-Induced Lupus Erythematosus** (especially in slow acetylators).

Q: Which of the following conditions increases the risk of digoxin toxicity?

Administration of quinidine. **Explanation:** Digoxin has a narrow therapeutic index, making it prone to toxicity. The correct answer is **Administration of quinidine** due to two primary pharmacokinetic interactions: 1. **Displacement:** Quinidine displaces digoxin from tissue binding sites (skeletal muscle). 2. **Reduced Excretion:** It inhibits P-glycoprotein (P-gp) in the renal tubules, significantly reducing the renal clearance of digoxin. This can lead to a doubling of plasma digoxin levels. **Analysis of Incorrect Options:** * **B. Hyperkalemia:** Potassium and digoxin compete for the same binding site on the **Na+/K+ ATPase pump**. Therefore, *hypokalemia* (low potassium) increases digoxin binding and toxicity, whereas hyperkalemia actually antagonizes digoxin’s effects. * **C. Hypermagnesemia:** *Hypomagnesemia* is a known risk factor for digoxin toxicity. Magnesium acts as a cofactor for the Na+/K+ ATPase pump; its deficiency sensitizes the myocardium to arrhythmias. * **D. Hypocalcemia:** Digoxin works by increasing intracellular calcium. *Hypercalcemia* (high calcium) synergizes with digoxin, increasing the risk of "stone heart" and arrhythmias. Hypocalcemia generally reduces this risk. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Toxicity Factors:** "Hypo K, Hypo Mg, Hyper Ca" (Low K, Low Mg, High Ca). * **Drug Interactions:** Apart from quinidine, **Verapamil, Amiodarone, and Spironolactone** also increase digoxin levels by inhibiting P-gp. * **Early Sign of Toxicity:** Gastrointestinal symptoms (anorexia, nausea, vomiting). * **Characteristic Sign:** Xanthopsia (yellowish-green vision). * **ECG Finding:** "Reverse Tick" or "Sagging" ST-segment depression. * **Antidote:** Digoxin-specific antibody fragments (DigiFab).

Q: Which of the following conditions increases the risk of digoxin toxicity?

Administration of quinidine. **Explanation** Digoxin has a narrow therapeutic index, making the understanding of drug interactions and electrolyte imbalances crucial for NEET-PG. **Why Quinidine is Correct:** Quinidine increases digoxin levels through two primary mechanisms: 1. **Displacement:** It displaces digoxin from tissue binding sites (skeletal muscle). 2. **Reduced Excretion:** It inhibits **P-glycoprotein (P-gp)** in the renal tubules, significantly reducing the renal clearance of digoxin. When co-administered, the dose of digoxin should typically be halved to prevent toxicity. **Analysis of Incorrect Options:** * **Hyperkalemia (B):** Potassium and digoxin compete for the same binding site on the **Na+/K+ ATPase pump**. Therefore, *hypokalemia* (low K+) increases digoxin binding and toxicity, while hyperkalemia antagonizes digoxin's effects. * **Hypermagnesemia (C):** *Hypomagnesemia* is a known risk factor for toxicity. Magnesium acts as a cofactor for the Na+/K+ ATPase pump; its deficiency sensitizes the heart to digitalis-induced arrhythmias. * **Hypocalcemia (D):** Digoxin works by increasing intracellular calcium. Therefore, **Hypercalcemia** (high Ca2+) synergizes with digoxin, increasing the risk of arrhythmias ("Stone Heart"). Hypocalcemia actually reduces the risk. **High-Yield Clinical Pearls for NEET-PG:** * **Electrolytes predisposing to toxicity:** Hypokalemia, Hypomagnesemia, and Hypercalcemia. * **Other drugs increasing Digoxin levels:** Verapamil, Amiodarone, and Spironolactone (all inhibit P-gp). * **Most common arrhythmia:** Ventricular Bigeminy. * **Most specific arrhythmia:** Atrial Tachycardia with AV block. * **Antidote:** Digoxin Immune Fab (Digibind).

Q: A 25-year-old primigravida delivered an infant with clubfoot. During her pregnancy, she was diagnosed with oligohydramnios and did not receive proper care. She was also taking certain medications during pregnancy. Which of the following medications is most likely to have caused oligohydramnios in this patient?

Enalapril. **Explanation:** The correct answer is **Enalapril (Option B)**. Enalapril is an ACE (Angiotensin-Converting Enzyme) inhibitor, which is strictly contraindicated in the second and third trimesters of pregnancy (FDA Category D). **Mechanism of Action:** ACE inhibitors cross the placenta and interfere with the fetal renin-angiotensin system. This leads to **fetal hypotension** and **decreased renal perfusion**, resulting in fetal renal tubular dysgenesis and anuria/oliguria. Since fetal urine is the primary source of amniotic fluid in the second half of pregnancy, this causes **oligohydramnios**. Prolonged oligohydramnios leads to the **Potter sequence**, characterized by pulmonary hypoplasia, cranial deformities, and limb contractures like **clubfoot (talipes equinovarus)** due to uterine compression. **Analysis of Incorrect Options:** * **A. Insulin:** It is the drug of choice for managing diabetes in pregnancy. It does not cross the placenta and is not associated with oligohydramnios. In fact, uncontrolled maternal diabetes is more commonly associated with *polyhydramnios*. * **C. Ciprofloxacin:** This fluoroquinolone is generally avoided in pregnancy due to concerns regarding fetal cartilage damage (arthropathy), but it is not a known cause of oligohydramnios or renal failure. **High-Yield Clinical Pearls for NEET-PG:** * **ACE Inhibitor Fetopathy:** Includes oligohydramnios, hypocalvaria (hypoplasia of skull bones), renal failure, and IUGR. * **Drug of Choice for HTN in Pregnancy:** Labetalol (most common), Methyldopa, or Nifedipine. * **Oligohydramnios Definition:** Amniotic Fluid Index (AFI) < 5 cm or Single Deepest Pocket (SDP) < 2 cm. * **Other drugs causing Oligohydramnios:** NSAIDs (e.g., Indomethacin) due to constriction of the ductus arteriosus and reduced fetal renal blood flow.

Q: All of the following drugs are Class I anti-arrhythmic drugs EXCEPT?

Sotalol. **Explanation:** The classification of anti-arrhythmic drugs is based on the **Vaughan-Williams classification**, which categorizes drugs according to their primary mechanism of action on the cardiac action potential. **Why Sotalol is the correct answer:** Sotalol is a **Class III anti-arrhythmic drug**. While it possesses non-selective beta-blocking properties (Class II), its primary anti-arrhythmic effect is the **blockade of potassium (K+) channels**. This action prolongs the phase 3 repolarization, thereby increasing the action potential duration (APD) and the effective refractory period (ERP). **Why the other options are incorrect:** Class I drugs are primarily **Sodium (Na+) channel blockers**. They are further subdivided based on their effect on the action potential duration: * **A (Quinidine) & B (Procainamide):** These are **Class IA** drugs. they moderately block Na+ channels and also have some K+ channel blocking activity, leading to a prolonged APD. * **C (Flecainide):** This is a **Class IC** drug. It is a potent Na+ channel blocker with a slow rate of dissociation, significantly slowing conduction (decreased slope of phase 0) with minimal effect on APD. **High-Yield NEET-PG Pearls:** * **Class IB (e.g., Lidocaine):** Shortens the APD and is the drug of choice for post-MI ventricular arrhythmias. * **Sotalol Paradox:** Despite being a Class III drug, it carries a high risk of **Torsades de Pointes** due to QT interval prolongation. * **Mnemonic for Class I:** "**D**ouble **Q**uarter **P**ounder (IA: Disopyramide, Quinidine, Procainamide), **L**ettuce **M**ayo **T**omato (IB: Lidocaine, Mexiletine, Tocainide), **F**ries **P**lease (IC: Flecainide, Propafenone)."

Q: Which alpha-blocker is used as an antihypertensive agent?

Prazosin. **Explanation:** **Prazosin** is the correct answer because it is a **selective alpha-1 ($\alpha_1$) adrenergic receptor antagonist**. By blocking $\alpha_1$ receptors on vascular smooth muscle, it causes vasodilation of both arterioles and veins, leading to a decrease in peripheral vascular resistance and blood pressure. Unlike non-selective alpha-blockers (like Phenoxybenzamine), Prazosin does not block $\alpha_2$ receptors; therefore, it does not cause significant reflex tachycardia, making it suitable for hypertension management. **Analysis of Incorrect Options:** * **Alpha-methyl DOPA (Option A):** This is a **centrally acting alpha-2 ($\alpha_2$) agonist**. It is converted to alpha-methylnorepinephrine, which stimulates central $\alpha_2$ receptors to decrease sympathetic outflow. While used for hypertension (especially in pregnancy), it is not an alpha-blocker. * **Clonidine (Option C):** Similar to Methyldopa, Clonidine is a **central $\alpha_2$ agonist**. It reduces blood pressure by decreasing sympathetic tone but is categorized as an agonist, not a blocker. * **Propranolol (Option D):** This is a **non-selective beta-blocker** ($\beta_1$ and $\beta_2$). It reduces blood pressure primarily by decreasing cardiac output and renin release, not by blocking alpha receptors. **NEET-PG High-Yield Pearls:** * **First-Dose Phenomenon:** Prazosin can cause marked orthostatic hypotension and syncope with the initial dose. Patients should be advised to take the first dose at bedtime. * **BPH:** Selective $\alpha_1$ blockers (Prazosin, Terazosin, Doxazosin) are excellent choices for hypertensive patients with **Benign Prostatic Hyperplasia (BPH)** as they relax the bladder neck. * **Raynaud’s Phenomenon:** Prazosin is also used off-label to treat digital vasospasm in Raynaud’s.

Question 1

What is the mechanism of action of sodium nitroprusside?

Accepted Answer

Increased guanylate cyclase

Answer

Increased cAMP

Answer

Calcium channel blockage

Answer

IC channel opener

Question 2

A 35-year-old woman presents with palpitations, and diagnostic tests confirm supraventricular tachycardia. Vagal maneuvers fail to provide an adequate response. What is the best therapy that can be advocated?

Accepted Answer

Adenosine

Answer

Amiodarone

Answer

Verapamil

Answer

Digoxin

Question 3

All of the following arrhythmias can be treated with Adenosine, except?

Accepted Answer

Arrhythmia with aberrant pathways

Answer

Atrial flutter

Answer

Paroxysmal atrial tachycardia

Answer

Supraventricular tachycardia

Question 4

Which of the following is NOT an arteriolar dilator?

Accepted Answer

Nitrates

Answer

Hydralazine

Answer

Minoxidil

Answer

Nifedipine

Question 5

Which of the following conditions increases the risk of digoxin toxicity?

Accepted Answer

Administration of quinidine

Answer

Hyperkalemia

Answer

Hypermagnesemia

Answer

Hypocalcemia

Question 6

Which of the following conditions increases the risk of digoxin toxicity?

Accepted Answer

Administration of quinidine

Answer

Hyperkalemia

Answer

Hypermagnesemia

Answer

Hypocalcemia

Question 7

A 25-year-old primigravida delivered an infant with clubfoot. During her pregnancy, she was diagnosed with oligohydramnios and did not receive proper care. She was also taking certain medications during pregnancy. Which of the following medications is most likely to have caused oligohydramnios in this patient?

Accepted Answer

Enalapril

Answer

Insulin

Answer

Ciprofloxacin

Answer

None of the above

Question 8

All of the following drugs are Class I anti-arrhythmic drugs EXCEPT?

Accepted Answer

Sotalol

Answer

Quinidine

Answer

Procainamide

Answer

Flecainide

Question 9

Which diuretic can be given in mild to moderate hypertension?

Accepted Answer

Thiazide

Answer

Loop diuretic

Answer

Osmotic diuretic

Answer

Potassium sparing diuretic

Question 10

Which alpha-blocker is used as an antihypertensive agent?

Accepted Answer

Prazosin

Answer

Alpha methyl DOPA

Answer

Clonidine

Answer

Propranolol

Cardiovascular Drugs — MCQs

Cardiovascular Drugs — MCQs

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