Encainide

Abstract

Encainide is a class IC antiarrhythmic agent having little or no effect on action-potential duration or maximum diastolic potential but decreasing the maximum rate of phase O depolarization as well as increasing atrial and ventricular effective refractory periods. In intact animals or humans, encainide increases the AH, PR, QRS, and H-V intervals while not affecting the sinus node cycle length or JT interval. QT interval increases only by the concomitant increase in the QRS interval. Encainide is metabolized to O-demethyl encainide (ODE) and 3-methoxy-ODE (MODE), both of which are also antiarrhythmics with similar pharmacology to encainide. Encainide and its metabolites have little negative inotropic activity and ancillary pharmacology. Consequently, encainide has little or no effect on hemodynamic variables in patients with either normal or compromised cardiac function. The drug is well tolerated, with side effects being mainly those associated with its local anesthetic activity such as blurred vision and dizziness. Encainide is particularly effective in patients with excessive premature ventricular complexes (PVCs) and less so in patients with sustained ventricular tachycardia (VT). Like all antiarrhythmics, encainide may aggravate or precipitate new arrhythmias (proarrhythmia). The overall incidence of proarrhythmia is about 10%, with less occurring in patients with PVCs and more in those with sustained VT; also, the incidence of proarrhythmia is higher in patients with underlying heart disease. Encainide is also effective for the treatment of supra-ventricular arrhythmias, including atrial fibrillation, PSVT (both PAF as well as reentry of the nodal or W-P-W type), and ectopic atrial tachycardia. Its dosage and role in antiarrhythmic therapy are discussed.

Encainide, a class Ic anti-arrhythmic agent, blocks voltage-dependent potassium channels in coronary artery smooth muscle cells

“…Class I anti-arrhythmic drugs target Na + channels and are divided into classes Ia–c according to their degree of inhibition on Na + channels [ 4 ]. Encainide is a class Ic anti-arrhythmic drug used since the 1980s [ 7 ]. It is a safe and well-tolerated anti-arrhythmic agent, with some minor side effects such as dizziness, headache, and nausea [ 8 , 9 ].…”

Controlling cardiac arrhythmias: To delay conduction or to prolong refractoriness

“…As emphasized by Antonaccio et al [4], this is particularly so in the case of the prophylactic control of paroxysmal supraventricular tachyarrhythmias and atrial fibrillation. As emphasized by Antonaccio et al [4], this is particularly so in the case of the prophylactic control of paroxysmal supraventricular tachyarrhythmias and atrial fibrillation.…”

“…Gomoll, and Byrne [4] provide a comprehensive review of the pharmacodynamic, electrophysiologic, and pharmacokinetic properties, and the developing clinical role, of encainide in cardiac arrhythmias. Gomoll, and Byrne [4] provide a comprehensive review of the pharmacodynamic, electrophysiologic, and pharmacokinetic properties, and the developing clinical role, of encainide in cardiac arrhythmias.…”

“…Gomoll, and Byrne [4] provide a comprehensive review of the pharmacodynamic, electrophysiologic, and pharmacokinetic properties, and the developing clinical role, of encainide in cardiac arrhythmias. Therefore, the issue that is of much importance, and one that is perhaps not emphasized enough by Antonaccio et al [4], is whether encainide and similar drugs exert their antiarrhythmic effects largely by interfering with conduction. Another feature that merits emphasis is the differential effect on repolarization between Purkinje fibers and ventricular muscle fibers.…”