Cardiac glycosides – Digitalis MCQs With Answer

Cardiac glycosides – Digitalis MCQs With Answer

Cardiac glycosides, especially digoxin and digitoxin, are cornerstone drugs in B. Pharm pharmacology covering mechanism of action, pharmacokinetics, therapeutic uses, toxicity and drug interactions. These agents inhibit the Na+/K+-ATPase, increase intracellular Ca2+, produce positive inotropy and negative chronotropy, and are used in heart failure and rate control of atrial fibrillation. Important keywords include digoxin, digitoxin, Na+/K+-ATPase inhibition, narrow therapeutic index, serum digoxin monitoring, drug interactions (quinidine, verapamil, amiodarone), electrolyte effects, and digoxin immune Fab. This focused review helps students master clinical pharmacology and safe use of digitalis. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which is the primary molecular mechanism of action of digoxin in cardiac myocytes?

• Activation of beta-1 adrenergic receptors
• Inhibition of Na+/K+-ATPase
• Blockade of L-type calcium channels
• Stimulation of phosphodiesterase

Correct Answer: Inhibition of Na+/K+-ATPase

Q2. Which clinical indication is a primary therapeutic use of digoxin?

• First-line therapy for hypertension
• Treatment of bacterial endocarditis
• Rate control in atrial fibrillation and symptomatic heart failure
• Acute management of myocardial infarction

Correct Answer: Rate control in atrial fibrillation and symptomatic heart failure

Q3. How does inhibition of Na+/K+-ATPase by digoxin increase cardiac contractility?

• Direct activation of sarcoplasmic reticulum Ca2+ channels
• Increased intracellular Na+ reduces Na+/Ca2+ exchanger activity, raising intracellular Ca2+
• Enhanced beta-adrenergic receptor sensitivity
• Inhibition of intracellular phospholamban

Correct Answer: Increased intracellular Na+ reduces Na+/Ca2+ exchanger activity, raising intracellular Ca2+

Q4. Which electrocardiographic change is classically seen with therapeutic digoxin effect?

• Prolonged PR interval
• Prolonged QT interval
• Delta wave
• Peaked T waves

Correct Answer: Prolonged PR interval

Q5. Which visual disturbance is a recognized sign of digitalis toxicity?

• Central scotoma only
• Night blindness
• Yellow-green visual halos and blurred vision
• Loss of peripheral vision

Correct Answer: Yellow-green visual halos and blurred vision

Q6. What is the specific antidote for severe digoxin poisoning?

• Activated charcoal
• Calcium gluconate
• Digoxin immune Fab (antidigoxin Fab fragments)
• Sodium bicarbonate

Correct Answer: Digoxin immune Fab (antidigoxin Fab fragments)

Q7. Which electrolyte abnormality most increases the risk of digoxin toxicity?

• Hyperkalemia
• Hypokalemia
• Hypernatremia
• Hypermagnesemia

Correct Answer: Hypokalemia

Q8. Which drug commonly raises serum digoxin concentrations by reducing its clearance or displacing it from tissue binding?

• Rifampin
• Quinidine
• Phenobarbital
• Carbamazepine

Correct Answer: Quinidine

Q9. What is the primary route of elimination for digoxin that necessitates dose adjustment in renal impairment?

• Hepatic metabolism by CYP3A4
• Renal excretion unchanged
• Biliary excretion as conjugates
• Pulmonary elimination

Correct Answer: Renal excretion unchanged

Q10. How does digitoxin differ pharmacokinetically from digoxin?

• Digitoxin is renally excreted and has a shorter half-life
• Digitoxin undergoes extensive hepatic metabolism and has a longer half-life
• Digitoxin has no tissue binding and is rapidly cleared
• Digitoxin is only given intravenously due to poor oral absorption

Correct Answer: Digitoxin undergoes extensive hepatic metabolism and has a longer half-life

Q11. Which effect of digoxin contributes to its ability to control ventricular rate in atrial fibrillation?

• Direct stimulation of AV nodal conduction
• Enhanced vagal tone and slowed AV nodal conduction
• Increased sinoatrial node automaticity
• Blockade of potassium channels in the AV node

Correct Answer: Enhanced vagal tone and slowed AV nodal conduction

Q12. What is the traditional therapeutic serum concentration range for digoxin used in many clinical settings?

• 0.05–0.2 ng/mL
• 0.5–2.0 ng/mL
• 5–10 ng/mL
• 10–20 ng/mL

Correct Answer: 0.5–2.0 ng/mL

Q13. Which arrhythmia pattern is particularly suggestive of digoxin toxicity?

• Torsades de pointes
• Bidirectional ventricular tachycardia
• Atrial flutter with 2:1 block
• Sinus tachycardia without ectopy

Correct Answer: Bidirectional ventricular tachycardia

Q14. Which combination of ECG changes is characteristic of digoxin effect?

• Shortened PR, prolonged QT
• Prolonged PR, shortened QT
• Peaked T waves and wide QRS
• ST elevation in anterior leads

Correct Answer: Prolonged PR, shortened QT

Q15. Which antiarrhythmic increases digoxin plasma concentration and often requires dose reduction of digoxin?

• Lidocaine
• Flecainide
• Amiodarone
• Procainamide

Correct Answer: Amiodarone

Q16. Use of which diuretic most commonly predisposes patients to digoxin toxicity by causing hypokalemia?

• Spironolactone
• Furosemide
• Acetazolamide
• Amiloride

Correct Answer: Furosemide

Q17. Which monitoring parameters are essential when a patient is receiving digoxin?

• Only blood pressure and heart rate
• Serum digoxin level, renal function and electrolytes
• Chest X-ray weekly
• Liver enzymes daily

Correct Answer: Serum digoxin level, renal function and electrolytes

Q18. Which laboratory abnormality is more typical in acute life-threatening digoxin overdose?

• Hypokalemia due to renal wasting
• Hyperkalemia from inhibited cellular K+ uptake
• Marked hypernatremia
• Decreased serum magnesium only

Correct Answer: Hyperkalemia from inhibited cellular K+ uptake

Q19. Why does hypomagnesemia increase the risk of digoxin-induced arrhythmias?

• Magnesium directly displaces digoxin from plasma proteins
• Low Mg2+ potentiates automaticity and enhances digoxin-induced arrhythmogenesis
• Hypomagnesemia increases renal clearance of digoxin
• Magnesium deficiency reduces digoxin absorption

Correct Answer: Low Mg2+ potentiates automaticity and enhances digoxin-induced arrhythmogenesis

Q20. What is the best immediate therapy for a patient with ventricular arrhythmia and confirmed severe digoxin toxicity?

• Intravenous magnesium sulfate only
• Digoxin immune Fab fragments
• High-dose beta blockers
• Intravenous calcium chloride

Correct Answer: Digoxin immune Fab fragments

Q21. Which thyroid condition affects digoxin sensitivity or pharmacokinetics?

• Hyperthyroidism causes decreased sensitivity and increased clearance
• Hypothyroidism may increase sensitivity and decrease clearance
• Both conditions have no effect on digoxin
• Only euthyroid states affect digoxin handling

Correct Answer: Hypothyroidism may increase sensitivity and decrease clearance

Q22. How does digoxin affect AV nodal properties?

• Increases AV nodal conduction velocity and shortens refractory period
• Decreases AV nodal conduction velocity and prolongs refractory period
• No effect on AV node but increases ventricular automaticity
• Blocks His-Purkinje conduction selectively

Correct Answer: Decreases AV nodal conduction velocity and prolongs refractory period

Q23. Is digoxin considered safe for use in pregnancy when indicated for maternal arrhythmia or heart failure?

• No, it is absolutely contraindicated in pregnancy
• Yes, it is relatively safe and commonly used when indicated
• Only topical digoxin is safe in pregnancy
• It causes fetal structural defects and must be avoided

Correct Answer: Yes, it is relatively safe and commonly used when indicated

Q24. Why must digoxin dosing be individualized and frequently monitored clinically?

• Because it has a very wide therapeutic index
• Because plasma levels are unaffected by renal function
• Because digoxin has a narrow therapeutic index and variable pharmacokinetics
• Because it is poorly absorbed orally in all patients

Correct Answer: Because digoxin has a narrow therapeutic index and variable pharmacokinetics

Q25. Which pharmacokinetic property explains why digoxin concentrations accumulate in tissues?

• Low protein binding and minimal tissue uptake
• Large volume of distribution due to tissue binding, especially in muscle
• Rapid hepatic metabolism preventing tissue accumulation
• Exclusive confinement to plasma volume

Correct Answer: Large volume of distribution due to tissue binding, especially in muscle

Q26. What is the rationale for using a loading (digitalizing) dose when initiating digoxin therapy in acute situations?

• To immediately correct hypokalemia
• To rapidly achieve therapeutic tissue and plasma concentrations
• To prevent interaction with other drugs
• To induce rapid diuresis

Correct Answer: To rapidly achieve therapeutic tissue and plasma concentrations

Q27. Which electrolyte abnormality should be corrected to reduce risk of digoxin-induced arrhythmias?

• Hypomagnesemia
• Hyperphosphatemia
• Hypercalcemia only
• Hyponatremia only

Correct Answer: Hypomagnesemia

Q28. Which autonomic effect contributes to digoxin’s slowing of the ventricular rate in atrial fibrillation?

• Increased sympathetic outflow to the AV node
• Increased vagal tone reducing sinus and AV nodal firing
• Direct increase in SA node pacemaker current
• Selective blockade of beta-2 receptors

Correct Answer: Increased vagal tone reducing sinus and AV nodal firing

Q29. Which conduction disturbance is a severe manifestation of digoxin toxicity?

• Wolff-Parkinson-White pattern without block
• Complete heart block
• Sinus bradycardia only
• Isolated first-degree AV block without symptoms

Correct Answer: Complete heart block

Q30. When is the optimal time to draw a serum sample for accurate digoxin level measurement?

• Immediately after an oral dose
• At random regardless of dosing time
• Trough level just before the next dose or at least 6–8 hours post-dose
• Within 30 minutes of IV administration

Correct Answer: Trough level just before the next dose or at least 6–8 hours post-dose

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

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