Antiarrhythmic Drugs Flashcards

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Questions and Answers

What is the general job of anti-arrhythmic drugs?

Increases potential to help reduce action potential and slow down beating of heart to stop arrhythmia.

What is excitability?

Changes in resting membrane potential.

What is conduction?

Slope of phase 0.

What is the refractory period?

Phases 1-3. Signup and view all the answers

What is automaticity?

Slope of phase 4; Na+ / Ca++ influx; K+ efflux; SNS / ischemia increases slope and automaticity; PNS decreases slope and automaticity. Signup and view all the answers

Calcium channel blockade drugs will extend what interval in an ECG?

P-R interval. Signup and view all the answers

Potassium channel blockade drugs will extend what interval in an ECG?

Q-T interval. Signup and view all the answers

Na+ channel blockers are in what class and what is their effect?

Class IA, IB, IC; decrease phase 0 upstroke rate & phase 4 slope, resulting in an increased threshold. Signup and view all the answers

Beta blockers are in what class and what is their effect?

Class II; decrease phase 4 slope. Signup and view all the answers

K+ channel blockers are in what class and what effect do they have?

Class III; increase action potential duration. Signup and view all the answers

Ca++ channel blockers are in what class and what effect do they have?

Class IV; decrease phase 4 slope. Signup and view all the answers

What general effect does adenosine have?

Increase diastolic potential; opens K+ channels. Signup and view all the answers

What are general characteristics of Na+ channels?

Resting (closed) - no ion movement; Open activated channel - Na in; Inactivated channel - no ion conduction; Use-dependent blockade. Signup and view all the answers

What are 3 Class 1a drugs?

Quinidine, procainamide, disopyramide. Signup and view all the answers

What is the general mechanism of Class 1a drugs?

Block Na+ channels (fast inward) phase 0; also block K+ channels (prolongs refractory period). Signup and view all the answers

What are the ADRs of Quinidine?

GI disturbances, cinchonism, Torsade de pointes, cardiac depression. Signup and view all the answers

What are the ADRs of Procainamide?

Formation of antinuclear antibody (ANA), lupus-like syndrome, rash, fever. Signup and view all the answers

Study Notes

General Function of Antiarrhythmic Drugs

Reduce action potential and slow heart rate to manage arrhythmias.

Key Concepts in Cardiac Electrophysiology

Excitability: Refers to changes in resting membrane potential.
Conduction: Defined by the slope of phase 0 of the action potential.
Refractory Period: Comprised of phases 1 through 3 where the heart is less responsive to stimulation.
Automaticity: Related to the slope of phase 4; involves Na+/Ca++ influx and K+ efflux, affected by SNS (increases slope) and PNS (decreases slope).

ECG Intervals Affected by Drug Classes

Calcium Channel Blockers: Extend the P-R interval on an ECG.
Beta Blockers: Also extend the P-R interval.
Potassium Channel Blockers: Prolong the Q-T interval.

Antiarrhythmic Drug Classes

Na+ Channel Blockers (Class I: IA, IB, IC): Decrease phase 0 upstroke rate and phase 4 slope; increase threshold for depolarization.
Beta Blockers (Class II): Decrease phase 4 slope.
K+ Channel Blockers (Class III): Increase action potential duration.
Ca++ Channel Blockers (Class IV): Decrease phase 4 slope.
Adenosine: Increases diastolic potential and opens K+ channels.

Characteristics of Sodium Channels

Resting state: Closed, no ion movement.
Activated state: Open, Na+ influx.
Inactivated state: No ion conduction.
Use-dependent blockade: Drug effect increases with faster activation rates.

Class IA Antiarrhythmic Drugs

Examples: Quinidine, Procainamide, Disopyramide.
Mechanism: Block Na+ channels in phase 0 and K+ channels, leading to prolonged refractory period.
Clinical Use: Effective for supraventricular and ventricular arrhythmias.

Quinidine

Class 1a antiarrhythmic and antimalarial derived from quinine.
Administered mainly in sustained-release tablets; less commonly used IV due to hypotension risk.
Commonly indicated for chronic control of both supraventricular and ventricular arrhythmias.

ADRs of Quinidine

GI disturbances, tinnitus, visual disturbances (Cinchonism), and proarrhythmias like Torsade de Pointes.
Possible drug interactions with digoxin, leading to increased toxicity.

Procainamide

Class 1a antiarrhythmic with fewer anticholinergic effects compared to Quinidine.
Indicated mainly for ventricular arrhythmias, with good oral bioavailability and short half-life.
Pharmacokinetics involve renal excretion and biotransformation to active metabolite (N-acetylprocainamide).

ADRs of Procainamide

High incidence of antinuclear antibodies (ANA) formation and lupus-like syndrome in some patients.
Risk of agranulocytosis, psychotic reactions, and overdose management with sodium lactate.

Disopyramide

Class 1a antiarrhythmic with unique clinical considerations (details not provided).

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Description

Explore essential concepts related to antiarrhythmic drugs, including their classes and functions. This quiz covers definitions and key terms that are critical for understanding how these medications affect heart rhythm. Test your knowledge and improve your grasp of antiarrhythmic pharmacology!