Cardiovascular Drugs Practice Questions

Q: What is the mechanism of action of sildenafil?

Inhibition of phosphodiesterase-5. **Explanation:** **Mechanism of Action:** Sildenafil is a selective inhibitor of **Phosphodiesterase-5 (PDE-5)**. In the corpus cavernosum, sexual stimulation leads to the release of Nitric Oxide (NO), which activates the enzyme guanylyl cyclase [1, 5]. This increases levels of **cyclic Guanosine Monophosphate (cGMP)**, causing smooth muscle relaxation and increased blood flow (erection) [3, 5]. PDE-5 is the enzyme responsible for the degradation of cGMP. By inhibiting PDE-5, sildenafil prevents the breakdown of cGMP, thereby enhancing and prolonging the vasodilatory effect of NO [1, 3]. **Analysis of Incorrect Options:** * **Option A (Adenosine deaminase):** Inhibited by drugs like **Pentostatin**, used in hairy cell leukemia. * **Option C (Aminopeptidase):** Inhibited by **Bestatin** (Ubenimex), an immunomodulator. * **Option D (Guanylyl cyclase):** Sildenafil actually *potentiates* the downstream effects of this enzyme; it does not inhibit it. Drugs like nitrates stimulate guanylyl cyclase [3]. **NEET-PG High-Yield Pearls:** * **Clinical Uses:** Erectile dysfunction and **Pulmonary Arterial Hypertension (PAH)** [1, 3]. * **Contraindication:** Must never be co-administered with **Nitrates** (e.g., Nitroglycerin) as it can cause life-threatening hypotension due to synergistic increases in cGMP [3]. * **Side Effects:** Headache, flushing, and **Cyanopsia** (blue-tinted vision) due to weak cross-inhibition of PDE-6 in the retina. * **Tadalafil vs. Sildenafil:** Tadalafil has a much longer half-life (approx. 18 hours) compared to sildenafil (approx. 4 hours).

Q: Which of the following drugs inhibits the enzyme responsible for the initial step of cholesterol synthesis?

Lovastatin. **Correct Option: A. Lovastatin**The "initial" or rate-limiting step of cholesterol biosynthesis is the conversion of **HMG-CoA to Mevalonate** [2]. This reaction is catalyzed by the enzyme **HMG-CoA reductase** [2]. Lovastatin belongs to the 'Statin' class of drugs, which are competitive inhibitors of this enzyme [1, 2]. By inhibiting this early step, statins reduce intracellular cholesterol levels, leading to the compensatory up-regulation of LDL receptors on hepatocytes and a subsequent decrease in plasma LDL levels [1, 2].**Analysis of Incorrect Options:** * **B. Gemfibrozil:** This is a Fibrate. Its primary mechanism is the activation of **PPAR-α** (Peroxisome Proliferator-Activated Receptor-alpha), which increases the activity of lipoprotein lipase (LPL), primarily lowering triglycerides rather than inhibiting cholesterol synthesis.* **C. Probucol:** This drug acts by increasing the rate of LDL catabolism and has antioxidant properties (preventing the oxidation of LDL). It does not inhibit the HMG-CoA reductase enzyme.* **D. Cholestyramine:** This is a **Bile Acid Sequestrant**. It binds to bile acids in the intestine, preventing their enterohepatic circulation. This forces the liver to use more cholesterol to synthesize new bile acids, thereby lowering systemic cholesterol indirectly.**High-Yield NEET-PG Pearls:** * **Rate-limiting enzyme:** HMG-CoA Reductase.* **Pleiotropic effects of Statins:** Beyond lowering lipids, they improve endothelial function, stabilize atherosclerotic plaques, and have anti-inflammatory effects [1].* **Adverse Effects:** Myopathy (monitored via CPK levels) and hepatotoxicity (monitored via LFTs).* **Contraindication:** Statins are strictly contraindicated in **pregnancy** (Teratogenic).

Q: Which of the following drugs is used to control hypertension emergencies?

Sodium nitroprusside. **Explanation:** **Sodium Nitroprusside** is the drug of choice for hypertensive emergencies because of its rapid onset (seconds) and short duration of action (1-2 minutes). It is a balanced vasodilator that acts by releasing Nitric Oxide (NO), which stimulates guanylyl cyclase to increase cGMP. This results in the relaxation of both **arterioles and venules**, leading to an immediate reduction in both preload and afterload. Its effects are easily titratable via continuous IV infusion, allowing for precise control of blood pressure. **Analysis of Incorrect Options:** * **Diazoxide (A):** Once used for emergencies, it is now largely obsolete. It is a K+ channel opener that causes profound arteriolar dilation but can lead to reflex tachycardia and hyperglycemia (by inhibiting insulin release). * **Hydralazine (B):** Primarily an arteriolar vasodilator. While used in hypertension, its onset is slower and its effects are less predictable than nitroprusside. It is, however, a preferred drug for **hypertension in pregnancy (Preeclampsia/Eclampsia)**. * **Nitroglycerine (C):** Acts predominantly as a **venodilator**. While used in hypertensive crises associated with acute coronary syndrome or acute heart failure, it is not the universal first-line agent for general hypertensive emergencies compared to nitroprusside or labetalol. **High-Yield Clinical Pearls for NEET-PG:** * **Cyanide Toxicity:** Sodium nitroprusside contains cyanide groups. Prolonged infusion can lead to cyanide/thiocyanate toxicity. The antidote is **Sodium Thiosulfate** or **Hydroxocobalamin**. * **Light Sensitivity:** Nitroprusside solution is unstable in light and must be wrapped in opaque foil. * **DOC for Aortic Dissection:** Esmolol or Labetalol (to reduce heart rate and shear stress). * **DOC for Hypertensive Emergency with Pheochromocytoma:** Phentolamine.

Q: Which of the following statements is not true regarding dobutamine?

Agonist of D1 and D2 receptors. ### Explanation **Dobutamine** is a synthetic catecholamine used primarily in the management of acute heart failure and cardiogenic shock. **1. Why Option A is the Correct Answer (The "Not True" Statement):** Unlike its parent compound dopamine, **dobutamine does not act on dopaminergic (D1 and D2) receptors.** It does not cause renal vasodilation or modulate prolactin release via dopaminergic pathways. This is a high-yield distinction often tested in exams to differentiate it from dopamine. **2. Analysis of Incorrect Options:** * **Option B (Derivative of dopamine):** This is **true**. Dobutamine is chemically synthesized by substituting the side chain of dopamine. * **Option C (Selective beta-agonistic action):** This is **true**. While it has some $\alpha_1$ activity, its predominant clinical effect is mediated through **$\beta_1$ receptors** (increasing contractility) and some $\beta_2$ activity (mild vasodilation). It is often referred to as an "inodilator." * **Option D (Reduced chances of arrhythmia than adrenaline):** This is **true**. Dobutamine is relatively less arrhythmogenic compared to adrenaline or isoproterenol because it increases myocardial contractility (inotropy) more significantly than it increases the heart rate (chronotropy). ### NEET-PG High-Yield Pearls * **Drug of Choice:** Dobutamine is the drug of choice for **cardiogenic shock** (when BP is stable) and **stress echocardiography** to detect viable myocardium. * **Receptor Profile:** Predominantly $\beta_1 > \beta_2 > \alpha_1$. * **Hemodynamic Effect:** It increases Cardiac Output (CO) while decreasing Systemic Vascular Resistance (SVR) and Pulmonary Capillary Wedge Pressure (PCWP). * **Half-life:** Very short (~2 minutes), requiring continuous IV infusion.

Q: Which of the following is NOT an extracardiac manifestation of Quinidine?

Congestive cardiac failure. **Explanation:** The question asks for the **extracardiac** manifestation that is *not* associated with Quinidine. **1. Why Congestive Cardiac Failure (CCF) is the correct answer:** Quinidine is a Class IA antiarrhythmic agent. While it can cause cardiac side effects such as QT prolongation, Torsades de Pointes (Quinidine syncope), and negative inotropic effects, **Congestive Cardiac Failure is classified as a cardiac manifestation**, not an extracardiac one. Therefore, it does not fit the criteria of the question. **2. Analysis of Extracardiac Manifestations (Incorrect Options):** * **Diarrhea:** This is the most common extracardiac side effect of Quinidine, occurring in approximately 30-50% of patients due to its local irritant effect on the GI tract. * **Cinchonism:** A classic triad of symptoms (tinnitus, headache, and visual disturbances/dizziness) resulting from toxicity. Since Quinidine is a cinchona alkaloid, this is a pathognomonic extracardiac side effect. * **Thrombocytopenia:** Quinidine can induce an immune-mediated destruction of platelets (Type II hypersensitivity), leading to petechiae and bleeding. **Clinical Pearls for NEET-PG:** * **Mechanism:** Blocks fast sodium channels (Phase 0) and potassium channels (Phase 3), leading to increased Action Potential Duration (APD) and Effective Refractory Period (ERP). * **Vagolytic Effect:** Quinidine has anticholinergic properties that can increase AV conduction; hence, it should be preceded by a beta-blocker or CCB when treating atrial flutter/fibrillation. * **Drug Interaction:** It significantly increases **Digoxin levels** by displacing it from tissue binding sites and reducing its renal clearance.

Q: What are the effects of beta-blockers on the heart, except for which of the following?

Decreases duration of systole. ### Explanation **Core Concept: Beta-Blockers and Cardiac Hemodynamics** Beta-blockers (e.g., Propranolol, Metoprolol) act by antagonizing $\beta_1$-adrenergic receptors in the heart. This leads to negative inotropic (force), chronotropic (rate), dromotropic (conduction), and lusitropic (relaxation) effects. **Why Option B is Correct:** Beta-blockers **increase**, rather than decrease, the duration of the cardiac cycle, primarily by **prolonging diastole**. By slowing the heart rate (negative chronotropy), the time available for ventricular filling (diastole) is significantly lengthened. The duration of systole remains relatively constant or may slightly increase due to the negative inotropic effect, but it is never "decreased" as a primary pharmacological action. **Analysis of Incorrect Options:** * **A. Decrease in heart rate:** This is the hallmark effect of beta-blockers due to the blockade of $\beta_1$ receptors in the SA node. * **C. Decreases cardiac output:** Since Cardiac Output = Stroke Volume × Heart Rate, the reduction in both contractility and heart rate leads to a decrease in overall cardiac output. * **D. Precipitates heart failure:** In patients with compensated heart failure or borderline cardiac reserve, the negative inotropic effect can acutely worsen the condition and precipitate acute decompensated heart failure. **High-Yield Clinical Pearls for NEET-PG:** * **Diastolic Filling:** The prolongation of diastole is beneficial in **Mitral Stenosis** (allows more time for blood to flow into the LV) and **Angina** (improves coronary perfusion, which occurs during diastole). * **Reverse Remodeling:** While they can precipitate acute failure, long-term use of specific beta-blockers (**Metoprolol, Bisoprolol, Carvedilol**) reduces mortality in chronic heart failure. * **Contraindication:** Avoid in Prinzmetal angina (may cause unopposed alpha-mediated vasoconstriction).

Q: Ouabain acts by inhibiting which of the following?

Na+/K+ ATPase. **Explanation:** **Mechanism of Action (Why D is correct):** Ouabain is a rapidly acting **cardiac glycoside**, similar to Digoxin. It works by reversibly inhibiting the **Na+/K+ ATPase pump** (specifically the alpha subunit) located on the myocardial sarcolemma. 1. Inhibition of this pump leads to an increase in intracellular **Sodium (Na+)**. 2. This high intracellular Na+ reduces the concentration gradient required for the **Na+/Ca2+ exchanger (NCX)** to function. 3. Consequently, calcium extrusion from the cell is decreased, leading to increased intracellular **Calcium (Ca2+)** levels. 4. This excess calcium is taken up by the Sarcoplasmic Reticulum, resulting in increased calcium release during subsequent depolarizations, leading to a **positive inotropic effect** (increased force of contraction). **Analysis of Incorrect Options:** * **A. Adenyl cyclase:** This enzyme converts ATP to cAMP. Drugs like Beta-agonists (Dobutamine) act via this pathway, not cardiac glycosides. * **B. Calcium channels:** Calcium channel blockers (e.g., Verapamil) inhibit these channels. Ouabain actually increases intracellular calcium indirectly. * **C. H+/K+ ATPase:** This is the "proton pump" found in gastric parietal cells. It is inhibited by Proton Pump Inhibitors (PPIs) like Omeprazole. **NEET-PG High-Yield Pearls:** * **Source:** Ouabain is derived from the seeds of *Strophanthus gratus*. * **Pharmacokinetics:** Unlike Digoxin, Ouabain is highly polar, poorly absorbed orally, and must be given **intravenously**. It has the fastest onset of action among glycosides. * **Vagal Effect:** Like Digoxin, it increases vagal tone, making it useful for rate control in atrial fibrillation (negative dromotropic effect). * **Toxicity:** Hypokalemia predisposes to toxicity because K+ and cardiac glycosides compete for the same binding site on the Na+/K+ ATPase pump.

Question 1

Which of the following statements about prasugrel is true when compared to clopidogrel?

Accepted Answer

Due to a higher risk of bleeding, prasugrel is contraindicated in patients with a history of stroke.

Answer

Prasugrel is slower acting than clopidogrel.

Answer

Prasugrel is a reversible antagonist of ADP receptors.

Answer

Prasugrel is effective orally, unlike clopidogrel.

Question 2

What is the mechanism of action of sildenafil?

Accepted Answer

Inhibition of phosphodiesterase-5

Answer

Inhibition of adenosine deaminase

Answer

Inhibition of Aminopeptidase

Answer

Inhibition of Guanylyl cyclase

Question 3

Which of the following drugs inhibits the enzyme responsible for the initial step of cholesterol synthesis?

Accepted Answer

Lovastatin

Answer

Gemfibrozil

Answer

Probucol

Answer

Cholestyramine

Question 4

Which of the following drugs is used to control hypertension emergencies?

Accepted Answer

Sodium nitroprusside

Answer

Diazoxide

Answer

Hydralazine

Answer

Nitroglycerine

Question 5

Which of the following statements is not true regarding dobutamine?

Accepted Answer

Agonist of D1 and D2 receptors

Answer

Derivative of dopamine

Answer

Selective beta-agonistic action

Answer

Reduced chances of arrhythmia than adrenaline

Question 6

Which of the following is NOT an extracardiac manifestation of Quinidine?

Accepted Answer

Congestive cardiac failure

Answer

Diarrhea

Answer

Cinchonism

Answer

Thrombocytopenia

Question 7

What are the effects of beta-blockers on the heart, except for which of the following?

Accepted Answer

Decreases duration of systole

Answer

Decrease in heart rate

Answer

Decreases cardiac output

Answer

Precipitates heart failure

Question 8

Which one of the following best represents the mechanism of action and electrocardiographic effect of diltiazem?

Accepted Answer

Calcium channel blockade; increased PR interval

Answer

Calcium channel blockade; increased QT interval

Answer

Adrenergic receptor blockade; decreased QT interval

Answer

Potassium channel blockade; increased QRS duration

Question 9

Which potent antiarrhythmic drug has little negative inotropic effect, making it valuable in patients with poor left ventricular function?

Accepted Answer

Digoxin

Answer

Amlodipine

Answer

Bidoprolo

Answer

Amiodarone

Question 10

Ouabain acts by inhibiting which of the following?

Accepted Answer

Na+/K+ ATPase

Answer

Adenyl cyclase

Answer

Calcium channels

Answer

H+/K+ ATPase

Cardiovascular Drugs — MCQs

Cardiovascular Drugs — MCQs

On this page

Practice by Chapter

Want unlimited practice?