Class IC antiarrhythmic agents

Glass IG Antiarrhythmic Agents. Class IC antiarrhythmic agents have marked local anesthetic effects. They slow the rapid inward sodium current producing marked phase 0 depression and slow conduction. Action potential duration of ventricular muscle is increased, ie, prolonged repolarization, but decreased in the His-Purkinie system by these agents. The effects on the ECG are increased PR interval, marked prolongation of the... 

Proarrhythmic effects of antiarrhythmic drugs In the Cardiac Arrhythmia Suppression Trial (CAST) treatment with encainide and flecainide, two class IC antiarrhythmic agents, successfully prevented ventricular ectopic beats in patients who had myocardial infarction. However, continued therapy with either drug was associated with a two- to three-fold increase in death due to cardiac arrhythmias. Similar results were reported for moricizine. Increased death was probably due to drug-induced fatal arrhythmias triggered by recurrent myocardial ischemia. 

Class Ic antiarrhythmic agents are powerful inhibitors of the fast sodium channel. They cause... 

Fig. 15.21) is an orally active class Ic antiarrhythmic agent that underwent clinical trials and for which a number of soft analogs... 

Flecainide acetate is a class Ic antiarrhythmic agent which was developed in the Riker Laboratories as part of a broad-based project investigating the effect of fluorine substitution on local anaesthetic or antiarrhythmic activity. The details concerning the development of this drug have been reported. ... 

The Class I antiarrhythmic agents inactivate the fast sodium channel, thereby slowing the movement of Na" across the cell membrane (1,2). This is reflected as a decrease in the rate of development of phase 0 (upstroke) depolarization of the action potential (1,2). The Class I agents have potent local anesthetic effects. These compounds have been further subdivided into Classes lA, IB, and IC based on recovery time from blockade of sodium channels (11). Class IB agents have the shortest recovery times (t1 ) Class lA compounds have moderate recovery times (t 2 usually <9 s) and Class IC have the longest recovery times (t 2 usually >9 s). 

PVC s alone with Class IC drugs was not sufficient to reduce mortality in the specific post-infarction population chosen for the CAST study. The failure of Class IC agents in the CAST study and their low efficacy in preventing induction of SVT during electrophysiological testing has increased the interest in alternative approaches to antiarrhythmic therapy, particularly towards Class III agents, a number of which are in Phase II clinical evaluation. 

This Class IC drug shows actions similar to those of flecainide. Propafenone [proe POF en one], like flecainide, slows conduction in all cardiac tissues and is considered a broad spectrum antiarrhythmic agent. 

Many patients undergoing ICD implantations are also on antiarrhythmic drug (AAD) therapy, and the effects of AADs on DFTs should be taken into consideration. Class IC and IB agents, such as encainide, flecainide, lidocaine, and... 

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