Antiarrhythmics

Question 1

Describe the mechanism of action of class IA antiarrhythmics (quinidine and procainamide)

Answer 1

block Na+ channels in normal and depolarized (“sick”) cells; prolong repolarization after the action potential and increasing the refractory period by blocking K+ channels

Question 2

What are the side effects of class IA antiarrhythmics (quinidine and procainamide)?

Answer 2

Frequent toxicity- fever, diarrhea, arrhythmias like Torsades de Pointes, long AT syndrome

Question 3

What are the clinical indications for class IA antiarrhythmics (quinidine, procainamide)?

Answer 3

Atrial and ventricular arrhythmias; quinidine suppresses A fib.

Question 4

When are class IA antiarrhythmics contraindicated?

Answer 4

Only use in EXTREME caution in patients w/ complete AV block

Question 5

Name the class IB antiarrhythmics.

Answer 5

lidocaine and mexiletine

Question 6

Describe the mechanism of action of class IB antiarrhythmics (lidocaine and mexiletine).

Answer 6

They block Na+ channels in depolarized (“sick”) cells and increase K+ permeability. Decrease automaticity of Purkinje fibers

Question 7

What are the side effects of class IB antiarrhythmics (lidocaine and mexiletine)?

Answer 7

Respiratory arrest, convulsion d/t blockage of inhibitory transmission in the brain

Question 8

What are the clinical indications for class IB antiarrhythmics (lidocaine and mexiletine)?

Answer 8

Ventricular arrhythmias

• mexiletine treats long QT syndrome
• lidocaine can only be given IV

Question 9

Name the class IC antiarrhythmics.

Answer 9

Flecainide

Question 10

Describe the mechanism of action of class IC antiarrhythmics (flecainide).

Answer 10

Blocks Na+ channels in normal and depolarized (“sick”) cells with no effect on repolarization.

*the action potential duration increases like class IA drgus but by a different mechanism so they are less likely to cause torsades de pointes

Question 11

What are the clinical indications for class IC antiarrhythmics (flecainide)?

Answer 11

Ventricular arrhythmias; can suppress PVCs but are shown to increase mortality when used after MI to tx asymptomatic PVCs

Question 12

Name the class II antiarrhythmics.

Answer 12

Metoprolol

Question 13

Describe the mechanism of action of class II antiarrhythmics (metoprolol).

Answer 13

Adrenergic beta-blocker; decreases SA nodal rate and AV conduction by blocking sympathetic input

Question 14

What are the clinical indications for class II antiarrhythmics (metoprolol)?

Answer 14

Atrial tachycardias; proven effective in reducing mortality s/p MI

**DO NOT use in WPW patients

Question 15

Name the class III antiarrhythmics.

Answer 15

Amiodarone, sotalol

Question 16

Describe the mechanism of action of class III antiarrhythmics (amiodarone, sotalol).

Answer 16

block K+ efflux during phase 3 and beta receptor blockade

*amiodarone also has a lesser blockade on Ca++ channels, increasing the refractory period

Question 17

What are the side effects of class III antiarrhythmics (amiodarone, sotalol)?

Answer 17

Prolonged QT that can lead to torsades de pointes.

*amiodarone- also causes pulm fibrosis in 1% of patients, thyroid dysfunction, liver toxicity, photosensitivity from corneal deposits

Question 18

What possible drug interactions should you watch out for with amiodarone?

Answer 18

Simvastatin (can increase risk of rhabdo b/c amiodarone inhibits the CYP enzyme that metabolizes simvastatin)

Question 19

What are the clinical indications for amiodarone (class III antiarrhythmic)?

Answer 19

at low doses suppresses A fib; high doses supress ventricular arrhythmias

*drug of choice in cardiac arrest

Question 20

What are the clinical indications for sotalol (class III antiarrhythmic)?

Answer 20

Supraventricular and ventricular arrhythmias; used for pts w/ ICD

Question 21

Name the class IV antiarrhythmics.

Answer 21

verapamil, diltiazem

Question 22

Describe the mechanism of action of class IV antiarrhythmics (verapamil, diltiazem).

Answer 22

Ca++ channel blockers (L-type). Slow the conduction at the SA and AV nodes in depolarized fibers

Question 23

What are the side effects of class IV antiarrhythmics (verapamil, diltiazem)?

Answer 23

Can cause edema not reflective of cardiac fxn in 33% of pts

Question 24

What are the clinical indications of class IV antiarrhythmics (verapamil, diltiazem)?

Answer 24

SVT, A fib, A flutter

Question 25

Name the class IA antiarrhythmics.

Answer 25

quinidine, procainamide