Pharmacology Cardiovascular System Drugs 3 — Questions and Answers
Question 1: Loop diuretics such as furosemide act on which segment of the nephron?
- Proximal convoluted tubule
- Thick ascending limb of the Loop of Henle (Correct answer)
- Early distal convoluted tubule
- Collecting duct principal cells
Correct answer: Thick ascending limb of the Loop of Henle
Furosemide inhibits the Na-K-2Cl cotransporter (NKCC2) in the thick ascending limb of the Loop of Henle, producing potent diuresis.
Question 2: Which statin is considered most potent and is also a substrate of OATP1B1, making it susceptible to drug interactions with cyclosporine?
- Pravastatin
- Fluvastatin
- Rosuvastatin (Correct answer)
- Lovastatin
Correct answer: Rosuvastatin
Rosuvastatin is among the most potent statins and is transported into hepatocytes by OATP1B1; cyclosporine inhibits this transporter, raising rosuvastatin plasma levels.
Question 3: Digoxin toxicity is potentiated by hypokalemia because:
- Low potassium increases renal clearance of digoxin
- Potassium and digoxin compete for the same binding site on Na/K-ATPase (Correct answer)
- Hypokalemia increases digoxin absorption from the gut
- Low potassium activates the vagal reflex, masking toxicity
Correct answer: Potassium and digoxin compete for the same binding site on Na/K-ATPase
Potassium and digoxin compete for the same binding site on the Na/K-ATPase; low potassium means less competition and enhanced digoxin binding and toxicity.
Question 4: Sacubitril/valsartan (Entresto) improves heart failure outcomes by combining an ARB with an inhibitor of which enzyme?
- Angiotensin-converting enzyme (ACE)
- Neprilysin (Correct answer)
- Aldosterone synthase
- Renin
Correct answer: Neprilysin
Sacubitril inhibits neprilysin, which normally breaks down natriuretic peptides; blocking it raises BNP/ANP levels, promoting vasodilation and natriuresis.
Question 5: Which antiarrhythmic is the first-line IV agent for terminating paroxysmal supraventricular tachycardia (PSVT) due to AV nodal re-entry?
- Amiodarone
- Lidocaine
- Adenosine (Correct answer)
- Procainamide
Correct answer: Adenosine
Adenosine transiently blocks AV nodal conduction by activating A1 receptors, interrupting re-entrant circuits that sustain PSVT.
Question 6: Thiazide diuretics are contraindicated in which electrolyte imbalance because they worsen it?
- Hypernatremia
- Hypercalcemia (Correct answer)
- Hypomagnesemia
- Hyperchloremia
Correct answer: Hypercalcemia
Thiazides reduce urinary calcium excretion by enhancing distal tubule calcium reabsorption, making hypercalcemia worse.
Question 7: Ivabradine reduces heart rate by blocking which ion channel in sinoatrial node pacemaker cells?
- L-type calcium channels
- Funny current (If) channels (HCN channels) (Correct answer)
- Delayed rectifier potassium channels
- Inward sodium channels (Nav1.5)
Correct answer: Funny current (If) channels (HCN channels)
Ivabradine selectively inhibits the hyperpolarization-activated funny current (If) in the SA node, slowing spontaneous depolarization and heart rate.
Pharmacology Cardiovascular System Drugs 3
Loop diuretics such as furosemide act on which segment of the nephron?