Class I: Sodium channel blockers

Definition

Class I: Sodium channel blockers are a group of medications used to treat arrhythmias by inhibiting sodium influx in cardiac cells, thus stabilizing the heart's electrical activity. They are subdivided into Class IA, IB, and IC based on their specific effects on the action potential.

5 Must Know Facts For Your Next Test

1. Class I: Sodium channel blockers slow down the conduction velocity of electrical impulses in the heart.
2. They are divided into three subclasses: IA (moderate), IB (weak), and IC (strong) based on their potency and effects on the action potential duration.
3. Common drugs include Quinidine (IA), Lidocaine (IB), and Flecainide (IC).
4. These drugs can be proarrhythmic, meaning they have the potential to cause new or worsening arrhythmias.
5. Class I agents are primarily used for ventricular arrhythmias but can also be used for supraventricular arrhythmias depending on the subclass.

Review Questions

• What is the primary mechanism of action of Class I sodium channel blockers?
• Name one drug from each subclass of Class I sodium channel blockers.
• Explain why some Class I sodium channel blockers can be proarrhythmic.

Related terms

Action Potential: The change in electrical potential that occurs when a cell membrane is stimulated, leading to muscle contraction.

Arrhythmia: An irregular heartbeat caused by abnormalities in the heart's electrical activity.

Antiarrhythmic Drugs: Medications used to treat abnormal heart rhythms by affecting ion channels or other mechanisms within cardiac cells.