Antiarrhythmic drugs – classification, mechanism, uses MCQs With Answer

Antiarrhythmic drugs – classification, mechanism, uses MCQs With Answer

Antiarrhythmic drugs are a core topic in cardiovascular pharmacology for B.Pharm students. This introduction covers classification (Vaughan Williams classes I–IV and newer agents), mechanisms of action such as sodium channel blockade, beta‑adrenergic antagonism, potassium channel inhibition and calcium channel blockade, key drugs (lidocaine, flecainide, amiodarone, sotalol, verapamil, adenosine), therapeutic uses, adverse effects including proarrhythmia and organ toxicities, pharmacokinetics and drug interactions. Understanding ECG correlates, indications for atrial versus ventricular arrhythmias, and monitoring requirements is essential for safe patient care. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What is the most commonly used classification system for antiarrhythmic drugs?

• British Cardiovascular Society classification
• Vaughan Williams classification
• WHO antiarrhythmic scheme
• European Society of Cardiology grouping

Correct Answer: Vaughan Williams classification

Q2. What is the primary mechanism of action of Class I antiarrhythmic drugs?

• Block L-type calcium channels in the AV node
• Block beta-adrenergic receptors to reduce conduction
• Block fast sodium channels to reduce phase 0 depolarization
• Block potassium channels to prolong repolarization

Correct Answer: Block fast sodium channels to reduce phase 0 depolarization

Q3. How do Class Ia, Ib and Ic drugs differ in their effects on action potential duration?

• Ia shortens AP, Ib prolongs AP, Ic markedly prolongs AP
• Ia prolongs AP, Ib shortens AP, Ic has little effect on duration
• All three shorten action potential duration equally
• Ib prolongs AP, Ia has no effect, Ic shortens AP

Correct Answer: Ia prolongs AP, Ib shortens AP, Ic has little effect on duration

Q4. Which drug is a classical Class Ia antiarrhythmic used for atrial and ventricular arrhythmias?

• Lidocaine
• Procainamide
• Flecainide
• Amiodarone

Correct Answer: Procainamide

Q5. Which drug is a Class Ib antiarrhythmic preferred for acute ventricular arrhythmias, especially post‑MI?

• Quinidine
• Lidocaine
• Flecainide
• Verapamil

Correct Answer: Lidocaine

Q6. Which of the following is a Class Ic antiarrhythmic with strong sodium channel blockade?

• Procainamide
• Mexiletine
• Flecainide
• Sotalol

Correct Answer: Flecainide

Q7. What is the main mechanism of Class II antiarrhythmics?

• Potassium channel blockade to prolong repolarization
• Beta‑adrenergic receptor blockade reducing sympathetic tone
• Sodium channel blockade during phase 0
• Direct activation of muscarinic receptors at the AV node

Correct Answer: Beta‑adrenergic receptor blockade reducing sympathetic tone

Q8. Class III antiarrhythmics primarily act by which mechanism?

• Enhancing sodium‑potassium ATPase activity
• Blocking potassium channels to prolong repolarization and QT
• Blocking calcium channels in the SA node only
• Stimulating vagal tone to the AV node

Correct Answer: Blocking potassium channels to prolong repolarization and QT

Q9. Which drug is a Class III agent that also has significant beta‑blocking activity and can prolong the QT interval?

• Amiodarone
• Sotalol
• Verapamil
• Lidocaine

Correct Answer: Sotalol

Q10. What is the principal action of Class IV antiarrhythmics like verapamil and diltiazem?

• Block fast sodium channels in ventricles
• Inhibit L‑type calcium channels reducing AV nodal conduction
• Enhance potassium efflux to shorten the action potential
• Increase sympathetic stimulation of the heart

Correct Answer: Inhibit L‑type calcium channels reducing AV nodal conduction

Q11. Which drug is the recommended acute IV therapy for terminating paroxysmal supraventricular tachycardia (AVNRT)?

• Amiodarone
• Adenosine
• Oral propranolol
• Digoxin

Correct Answer: Adenosine

Q12. For acute ventricular rate control in atrial fibrillation, which IV drug is commonly used to slow AV nodal conduction?

• Diltiazem
• Lidocaine
• Flecainide
• Procainamide

Correct Answer: Diltiazem

Q13. Which antiarrhythmic is most strongly associated with pulmonary fibrosis and thyroid dysfunction?

• Quinidine
• Amiodarone
• Sotalol
• Lidocaine

Correct Answer: Amiodarone

Q14. Widening of the QRS complex on ECG is most characteristic of which class of antiarrhythmics?

• Class IV calcium channel blockers
• Class Ib agents
• Class Ic sodium channel blockers
• Class III potassium channel blockers

Correct Answer: Class Ic sodium channel blockers

Q15. Which drug is well known to increase the risk of torsades de pointes due to QT prolongation?

• Verapamil
• Sotalol
• Lidocaine
• Propranolol

Correct Answer: Sotalol

Q16. How does digoxin exert rate‑controlling effects in atrial fibrillation?

• By blocking L‑type calcium channels at the AV node
• By direct potassium channel opening in atrial tissue
• By inhibiting Na+/K+ ATPase and increasing vagal tone to slow AV conduction
• By strong beta‑adrenergic blockade of the SA node

Correct Answer: By inhibiting Na+/K+ ATPase and increasing vagal tone to slow AV conduction

Q17. Which antiarrhythmic has multi‑channel blocking properties (Na+, K+, Ca2+) and beta blockade, used for many atrial and ventricular arrhythmias?

• Procainamide
• Flecainide
• Amiodarone
• Mexiletine

Correct Answer: Amiodarone

Q18. Which antiarrhythmic class or drug is contraindicated in patients with significant structural heart disease due to proarrhythmic risk?

• Class Ib agents like lidocaine
• Class Ic agents like flecainide
• Class III agents like amiodarone
• Class IV agents like verapamil

Correct Answer: Class Ic agents like flecainide

Q19. Which agent is typically chosen as first‑line IV therapy for life‑threatening ventricular arrhythmias after myocardial infarction?

• Verapamil
• Lidocaine
• Quinidine
• Diltiazem

Correct Answer: Lidocaine

Q20. Which antiarrhythmic is associated with cinchonism (tinnitus, headache, visual disturbances)?

• Quinidine
• Amiodarone
• Propranolol
• Sotalol

Correct Answer: Quinidine

Q21. Which antiarrhythmic is a potent inhibitor of multiple CYP enzymes and can increase warfarin levels leading to bleeding risk?

• Procainamide
• Amiodarone
• Lidocaine
• Mexiletine

Correct Answer: Amiodarone

Q22. Which class of antiarrhythmics tends to shorten action potential duration in ventricular myocardium?

• Class Ia
• Class Ib
• Class Ic
• Class III

Correct Answer: Class Ib

Q23. Which property of amiodarone necessitates a loading dose and long monitoring due to its pharmacokinetics?

• Very short half‑life requiring continuous infusion
• Extensive tissue accumulation and very long half‑life
• Rapid renal elimination with active metabolites
• Strict first‑pass metabolism only

Correct Answer: Extensive tissue accumulation and very long half‑life

Q24. What is the recommended acute treatment for torsades de pointes?

• IV magnesium sulfate
• Oral propranolol
• IV lidocaine bolus
• IV verapamil

Correct Answer: IV magnesium sulfate

Q25. Ivabradine reduces heart rate by inhibiting which current in the sinoatrial node?

• L‑type calcium current (ICa-L)
• Delayed rectifier potassium current (IKr)
• Funny current (If) mediated by HCN channels
• Sodium current (INa)

Correct Answer: Funny current (If) mediated by HCN channels

Q26. Which ECG change is most commonly produced by Class Ia antiarrhythmics?

• Shortened QT interval
• Prolonged QT interval
• Decreased PR interval
• Peaked T waves only

Correct Answer: Prolonged QT interval

Q27. What does the term “proarrhythmia” mean in clinical pharmacology?

• Reduced heart rate from drug therapy
• Development or worsening of arrhythmias caused by antiarrhythmic drugs
• Complete suppression of all arrhythmias
• Drug‑induced hypertension

Correct Answer: Development or worsening of arrhythmias caused by antiarrhythmic drugs

Q28. Which monitoring test is essential during long‑term amiodarone therapy?

• Serum creatinine only
• Thyroid function tests
• Fasting blood glucose only
• Serum magnesium only

Correct Answer: Thyroid function tests

Q29. Sotalol has dual actions; what are they?

• Calcium channel blockade and vagal stimulation
• Beta‑blockade and potassium channel blockade
• Sodium channel blockade and ACE inhibition
• Direct renin inhibition and potassium sparing

Correct Answer: Beta‑blockade and potassium channel blockade

Q30. Which drug is commonly used in a “pill‑in‑the‑pocket” approach for conversion of recent onset atrial fibrillation in patients without structural heart disease?

• Amiodarone
• Flecainide
• Digoxin
• Verapamil

Correct Answer: Flecainide

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.

Mail- Sachin@pharmacyfreak.com