propafenone

Propafenone is a class Ic antiarrhythmic agent used to treat certain cardiac rhythm disorders. It is indicated for the conversion to and maintenance of sinus rhythm in selected patients with paroxysmal atrial fibrillation or flutter, and for suppression of certain ventricular arrhythmias, typically in individuals without significant structural heart disease.

Propafenone acts primarily by blocking fast sodium channels in the heart, which slows conduction and depolarization in atrial, ventricular, and His-Purkinje tissue. It also possesses mild nonselective beta-adrenergic blocking properties, which can reduce heart rate and AV nodal conduction. These combined effects help stabilize abnormal rhythms but can also depress cardiac function in some patients.

Pharmacokinetics: after oral administration, propafenone is extensively metabolized in the liver, mainly by CYP2D6 to an active metabolite (5-hydroxypropafenone). Both the parent drug and the metabolite contribute to antiarrhythmic activity. The elimination half-life varies among individuals, influenced by CYP2D6 metabolism, and the drug is excreted in urine.

Contraindications and precautions: significant conduction abnormalities (second- or third-degree AV block), sick sinus syndrome without a pacemaker, cardiogenic shock, severe left ventricular dysfunction, or other conditions causing hypotension or heart failure. Caution is advised in patients with ischemic heart disease, electrolyte disturbances, or asthma/CAD due to beta-blocking effects. The drug can prolong the QT interval and provoke proarrhythmia, especially with electrolyte imbalance or concomitant QT-prolonging drugs. It should be avoided in patients with Wolff-Parkinson-White syndrome presenting with atrial fibrillation.

Adverse effects and interactions: common effects include taste disturbance (dysgeusia), dizziness, constipation, nausea, and fatigue; bradycardia or hypotension may occur. Drug interactions include inhibitors or inducers of CYP2D6, as well as other antiarrhythmics, digoxin, and anticoagulants. Pregnancy and lactation require careful consideration of risks and benefits.