How Do Class IA Antidysrhythmics Work?

Reviewed on 5/18/2021

WHAT ARE CLASS IA ANTIDYSRHYTHMICS AND HOW DO THEY WORK?

Antidysrhythmics, also known as antiarrhythmics, are drugs used to prevent abnormal cardiac rhythms such as atrial fibrillation, atrial flutter, ventricular tachycardia, and ventricular fibrillation. These drugs work by blocking sodium, potassium, and calcium channels in the heart muscles. Some drugs show autonomic effects.

Antiarrhythmic drugs are grouped into four main classes:

  • Class I, sodium-channel blockers;
  • Class II, beta-blockers;
  • Class III, potassium-channel blockers;
  • Class IV, calcium-channel blockers; and
  • miscellaneous antiarrhythmics or unclassified antiarrhythmics.

Class I antidysrhythmics block sodium channels (bind more tightly to cardiac tissue that is depolarizing a lot) and limit the electrical conductance of sodium over the cell membrane and reduce the rate of phase 4 (resting phase) depolarization in automatic cells. They are divided into subclasses a, b, and c.

Class IA antidysrhythmics block sodium channels that are in an open state and moderately delay channel recovery time. This results in slow conduction of electrical impulse through cardiac tissue, increased duration of action potential, and decreased slop of phase 0 depolarization. This prolongation of action potential corrects any irregular heartbeat. They also increase the effective refractory period (resting state in a depolarized cell and sodium channels are inactive in this phase) in ventricular action potentials. This suppresses atrial premature depolarizations which may lead to ventricular tachycardia. They may prolong action potential by blocking potassium channels as well.

Antidysrhythmic drugs do not improve the survival rate among patients with nonlife-threatening arrhythmias and may increase mortality in patients with structural heart disease.

HOW ARE CLASS IA ANTIDYSRHYTHMICS USED?

Class IA antidysrhythmics are used to prevent and treat:

QUESTION

Atrial fibrillation is a(n) ... See Answer

WHAT ARE SIDE EFFECTS OF CLASS IA ANTIDYSRHYTHMICS?

Class IA antidysrhythmics are used to prevent and treat:

Life-threatening ventricular arrhythmias (abnormal heartbeats that originate in the lower heart chambers)

Other common side effects include:

The information contained herein is not intended to cover all possible side effects, precautions, warnings, drug interactions, allergic reactions, or adverse effects. Check with your doctor or pharmacist to make sure these drugs do not cause any harm when you take them along with other medicines. Never stop taking your medication and never change your dose or frequency without consulting your doctor.

WHAT ARE DRUG NAMES OF CLASS IA ANTIDYSRHYTHMICS?

Drug names include:

Quinidine gluconate

References
https://www.medscape.com/answers/151456-195407/which-medications-in-the-drug-class-antidysrhythmics-ia-are-used-in-the-treatment-of-atrial-tachycardia

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