CV: Anti-arrhythmic Drugs

Question 1

What do antiarrhythmic drugs do?

Answer 1

Block voltage-activated (V/A) ion channels

Question 2

What are the classes of antiarrhythmic drugs?

Answer 2

Class IA: (V/A) Na+ channels; moderate rate of dissociation

Class IB: (V/A) Na+ channels; slow-dissociating

Class IC: (V/A) Na+ channels; slow-dissociating

Class II: beta-adrenoceptor agonists

Class III: (V/A) K+ channels; prolong AP duration

Class IV: (V/A) Ca2+ channels (reduce force of contraction)

Question 3

Class IA antiarrhythmic?

Answer 3

Disopyramide

Question 4

Mode of action of Disopyramide?

Answer 4

Blocks myocyte Na+ channels:

-slows down the depolarisation, Phase 0

Question 5

Side effects of Disopyramide?

Answer 5

Pulmonary fibrosis

Thyroid abnormalities

Question 6

Class IB drug?

Answer 6

Lignocaine

Question 7

Mode of action of Lignocaine?

Answer 7

Blocks myocyte Na+ channels:

-slows down the depolarisation, Phase 0

Question 8

Class IC antiarrhythmic?

Answer 8

Flecainide

Question 9

Mode of action of Flecainide?

Answer 9

Blocks myocyte Na+ channels:

-slows down the depolarisation, Phase 0

Question 10

Class II anthiarrhythmic?

Answer 10

Metoprolol

Question 11

Mode of action of Metoprolol?

Answer 11

Beta-adrenoceptor antagonist:

• blocks binding of adrenaline in the Nodal Cells
• slows down the nodal depolarisation (Phase 4), decreasing the rate of AP firing

Question 12

Class III antiarrhythmic?

Answer 12

Amiodarone

Question 13

Mode of action of Amiodarone?

Answer 13

Blocks K+ channels in myocytes:

-prolongs AP duration by prolonging the plateau phase

Question 14

Class IV antiarrhythmic?

Answer 14

Verapamil

Question 15

Mode of action of Verapamil?

Answer 15

Blocks Ca channels in cardiac nodal cells:

-Lowers the Phase 0 slope, reducing the rate of SA firing

Question 16

When is Digoxin used?

Answer 16

for AF and Heart failure

Question 17

Mode of action of Digoxin?

Answer 17

Blocks atrial-ventricular conduction

Question 18

When is Adrenaline used?

Answer 18

Anaphylactic shock (IM)
Cardiac arrest (IV)

Question 19

When is Atropine used?

Answer 19

First-line treatment of Severe bradycardia -