Antiarrhythmic Drug

Question 1

Name a class 1A drug

Answer 1

Procainamide (Na+ channel blocker)

Question 2

Mechanism of class 1A

Answer 2

• reduces rate of phase 0 rise (slows phase 0 depolarisation)
• reduces conductivity and automaticity
• increases effective refractory period and action potential duration

Question 3

Name class 1B drug

Answer 3

Lidocaine (Na+ channel blocker)

Question 4

Mechanism of class 1B

Answer 4

• reduces rate of phase 0 rise
• shortens shortens phase 3 repolarisation
• reduces automaticity
• reduce APD
  -NO CHANGE IN ERP AND CONDUCTIVITY

Question 5

Name class 1C drug

Answer 5

Flecainide (Na+ channel blocker)

Question 6

Mechanism of class 1C

Answer 6

• reduces rate of phase 0 rise
• shortens phase 3 repolarisation
• reduces conductivity and automaticity
• no effect on ERP and APD

For use in refractory ventricular tachycardia that tend to progress to VF

Question 7

Name class 2 drugs

Answer 7

Beta blockers like metoprolol and propranolol

Question 8

Mechanism of class 2

Answer 8

Reduces Phase 4 depolarization
Reduces automaticity
Prolonged AV conduction
Reduces heart rate and contractility
No change to APD, ERP

Question 9

Clinical use of class 2

Answer 9

Tachycardia caused by sympathetic activation
• Atrial fibrillation
• AV nodal reentrant tachycardia
• Reduces sudden arrhythmic death post-MI

Question 10

Name class 3

Answer 10

Amiodarone (potassium channel blockers)

Question 11

Mechanism of class 3

Answer 11

-Prolongs Phase 3 repolarization (no Phase 0 effect)
-Increases ERP and APD

Question 12

PK of amiodarone

Answer 12

Bioavailability: 35-65%.
Hepatic metabolism: desethylamiodarone (bioactive).
Elimination h1/2: 3-10 days (first 50%); several weeks (second 50%).
After discontinuation: effects are maintained for 1-3 months

Question 13

Clinical use of amiodarone

Answer 13

1. Be effective in maintaining normal sinus rhythm in patients with atrial fibrillation.
2. Be effective in the prevention of reentrant ventricular tachycardia.

Question 14

Side effects of amiodarone

Answer 14

Symptomatic bradycardia and heart block

Question 15

Name class 4

Answer 15

Non-DHP calcium channel blockers (Verapamil, Diltiazem)

Question 16

Mechanism of class 4

Answer 16

• Prolongs Phase 4 depolarization
  • Reduces conductivity on AV node
  • Increases ERP and APD

Question 17

Class 4 uses

Answer 17

Supraventricular tachycardia
hypertension
angina

Question 18

Class 4 side effect

Answer 18

Contraindication: patients with preexisting depressed cardiac function. hypotension

Question 19

Action of adenosine (emergency drug)

Answer 19

Suppression of atrioventricular nodal conduction and increases the AV nodal refractory period
stimulates cardiac K+ channel (KAch)
inhibits calcium current.

Question 20

Adenosine side effects

Answer 20

•flushing
•shortness of breath or chest burning
•Induction of AV block or AF
•headache , hypotension