Class Ic and Id agents

Question 1

describe class Ic agents general

Answer 1

Moricizine, flecainidine

• STRONGEST BINDING TO Na+ CHANNEL

–> slow on-off kinetics (strong effects on phase 0 depolarization)

–> lengthed QRS and APD

–> little effect on repolarization (QT unchanged)

Question 2

describe propafenone

Answer 2

• MOA: Strong inhibitor of Na+ channel

–> can inhibit Beta-adrenergic recetpors: marked structural similarity to propranolol

• TX: atrial arrhythmias, pSVT, and ventricular arrhythmias in patients with NO or MINIMAL HEART DISEASE and PRESEVERED VENTRICULAR FUNCTION

Question 3

Flecainide

Answer 3

• MOA:
• potent Na+ channel blockade = prolongs phase 0 and widens QRS
• Markedly slows intraventricular conduction
• Clinical applications:
• use only in tx of refractory life-threatening ectopic ventricular arrhythmia
• NOT CONSIDERED FIRST-LINE AGENT due to propensity for fetal proarrhythmic effects

Question 4

describe Class I agents

Answer 4

Beta-adrenergic antagonists

- DECREASE:

–> SA nodal automaticity (Phase 4)

–> AV nodal conduction

–> ventricular contractility

- Effective for supraventricular arrhythmias due to excessive sympathetic activity

• not very effective ins evere arrhythmias such as recurrent VT
• Are the ONLY ANTIARRHYTHMIC DRUGS FOUND TO BE CLEARLY EFFECTIVE IN PREVENTING SUDDEN CARDIAC DEATH IN PATEITNE WITH PRIOR MI