Class Ic anti-arrhythmic drugs: indications, contraindications and precautions
THE CONTEXT
Class Ic drugs include flecainide and propafenone and are used mainly for prevention of atrial fibrillation.
Class effects and clinical uses
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Class Ic drugs affect the slope of the action potential without changing its duration or the refractory period.
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They are used mainly for prophylaxis of atrial fibrillation, but are also effective for prophylaxis and treatment of supraventricular or ventricular arrhythmias.
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They are useful in WPW syndrome because they block conduction in accessory pathways.
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They should not be used after a previous myocardial infarction because they increase arrhythmia risk in this setting.
Flecainide
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Flecainide prevents atrial fibrillation. An intravenous infusion may be used for pharmacological cardioversion when atrial fibrillation has lasted less than 24 hours.
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Flecainide can cause slow atrial flutter with a paradoxically rapid ventricular rate. It should be combined with an AV node-blocking drug, such as a β-blocker, to control the ventricular rate.
Propafenone
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Propafenone also has some β-blocker, or class II, properties.
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Important interactions with digoxin, warfarin and cimetidine have been described.