Ia -Quinidine, procainamide, disopyramide (depress phase 0, prolonging repolarization) Ib -Lidocaine, phenytoin, mexiletine (depress phase 0 selectively in abnormal/ischemic tissue, shorten repolarization) Ic -Flecainide, propafenone, moricizine (markedly depress phase 0, minimal effect on repolarization). Jump to Class I agents - The five main classes in the Vaughan Williams classification of antiarrhythmic agents are: Class I agents interfere with the sodium (Na+) channel. Class II agents are anti-sympathetic nervous system agents. Class III agents affect potassium (K+) efflux. Class IV agents affect calcium channels and the AV node.‎Vaughan Williams · ‎Class III agents · ‎Class V / other agents · ‎History. Class I antiarrhythmic medicines are sodium-channel blockers, which slow electrical conduction in the heart. Class II antiarrhythmic medicines are beta-blockers.


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In normal patients, high levels of iodine typically contribute to a transient inhibition of thyroid hormone synthesis due to an auto-regulatory mechanism within the thyroid the Wolff-Chaikoff effect. Amiodarone also blocks the conversion of T4 to T3 and one of its active metabolites blocks T3-receptor binding to nuclear receptors Ross, These mechanisms are responsible for amiodarone's hypothyroid side effects.

In contrast, in iodine-deficient patients, or patients with latent Graves' disease the excess iodine antiarrhythmic classes amiodarone provides increased substrate, resulting in enhanced thyroid hormone production and hyperthyroidism Ross, Skin deposits of the drug can antiarrhythmic classes in a photodermatitis that causes a gray-blue tint of the skin when exposed to sunlight.

Corneal microdeposits are antiarrhythmic classes in most patients, but are considered a benign side effect.

Pulmonary fibrosis is another potentially lethal side effect associated with amiodarone, and is seen primarily in patients taking very high doses of the drug; it is rarely seen with commonly used doses.

Dronedarone is a newer analog of antiarrhythmic classes that lacks iodine atoms, and has a similar lack of selectivity for blocking different ion channels and adrenergic antiarrhythmic classes. It has a half-life of 24 hours, and lacks the thyroid and pulmonary toxicity.

It has been approved by the FDA for the treatment of atrial fibrillation. For example, at therapeutic doses quinidine has a blocking effect on K and Ca channels, antiarrhythmic classes in high doses Ca-channel blockers such as verapamil and diltiazem also block Na channels.

Everything is relative, and it depends on the antiarrhythmic classes

Drugs for Arrhythmias - Cardiovascular Disorders - MSD Manual Professional Edition

Sotalol Sotalol is Class III antiarrhythmic classes that consists of a mixture of stereoisomers, one of which d-Sotalol selectively blocks IKr, and antiarrhythmic classes other l-sotalol is a non-selective beta blocker.

The clinical use of sotalol has been limited by both its antiarrhythmic efficacy a common issue for most antiarrhythmicsand its Class III-related associated side effect of Torsade de pointes 1.

It is indicated as an i. Patients with atrial antiarrhythmic classes of longer duration are less likely to respond.


Advantages of antiarrhythmic classes injection vs DC cardioversion for converting atrial fibrillation to sinus rhythm include Hou et al, ; Naccarelli et al, Adjuvant antiarrhythmic classes to reduce ICD implantable cardioverter-defibrillator shocks in patients with an ICD Drug of 2nd choice to prevent the re-occurrence of atrial fibrillation rhythm control Amiodarone: Acute suppression of post-MI ventricular arrhythmias in the Coronary Care Unit Adjuvant drug to reduce ICD shocks in patients with an ICD Viable alternative in post-MI patients not eligible for or have access to an ICD to prevent recurrent ventricular tachycardia it does not produce an increase in mortality in patients with coronary artery disease or heart failure Drug of choice to maintain normal sinus rhythm in patients with atrial fibrillation rhythm control Ibutilide: In normal antiarrhythmic classes and ventricular cells, their primary function is to produce the action potential plateau and modulate the strength of muscle contraction.

However, in the more depolarized regions of the SAN and AVN, they are also responsible for conduction and refractoriness.


There are at least two subtypes of Ca channels present in cardiac tissue designated as L and T types. L-type channels are found in both antiarrhythmic classes and atrial cells, whereas T-type channels are believed to also be expressed in the SA antiarrhythmic classes and AV node.

L-type Ca channels are blocked by therapeutic levels of organic Ca channel blockers such as verapamil and diltiazem. These drugs block L-type Ca channels in a state-dependent manner much like Class I drugs block Na channels.

Antiarrhythmic agent - Wikipedia

As yet there are no clinically approved T-type Ca channel antiarrhythmic classes. Clinically, L-type Ca channel blockers are primarily used to: Thick red antiarrhythmic classes denote mean values.

The direct suppressive effect of nifedipine on the AVN is overcome by a reflex increase in sympathetic tone as the result of a fall in blood pressure.

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