Antidysrhythmic Drugs Pharmacology Cheat Sheet

Antidysrhythmic drugs are used to treat dysrthythmias, which is any deviation from the normal rhythm of the heart.

Mechanism of Action

Antidysrhythmic drugs work by correcting abnormal cardiac function. There are four classes of antidysrhytmics which each have a different mechanism of action.

• Class I drugs work on sodium channels, and are subdivided in a, b, and c classes.
• Class II drugs are beta-adrenergic blockers also called beta-blockers. These work by reducing or blocking sympathetic nervous system stimulation to the heart and thus reducing or blocking the transmission of impulses within the heart’s impulse conduction system.
• Class III drugs increase the APD by prlonging repolarization.
• Class IV drugs are calcium channel blockers which inhibit the calcium channels reducing the movement of calcium ions in the cells during action potentials.

Indications

They are used to treat dysrhythmias, and some classes are also used in the treatment of angina and hypertension.

Contraindictions

Include known drug allergies, as well as second or third-degree AV block, a bundle branch block, cardiogenic shock, sick sinus syndrome, and other major ECG changes.

Adverse Effects

Common adverse effects include hypersensitivity reactions, nausea, vomiting, diarrhea, dizziness, headache and blurred vision. Some antidysrhythmics are able to cause to dysrhythmias.

Toxicity

Another adverse effect is drug toxicity. The main toxic effect of antidysrhythmic drugs involve the heart, circulation and CNS.

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