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Encainide.
M J Antonaccio1, A W Gomoll, J E Byrne
1Bristol-Myers Pharmaceutical Research and Development Division, Wallingford, CT.
Cardiovascular Drugs and Therapy
|October 1, 1989
Summary
Encainide, a class IC antiarrhythmic, effectively treats supraventricular arrhythmias and premature ventricular complexes by altering cardiac electrical properties. While generally well-tolerated, it carries a risk of proarrhythmia, particularly in patients with underlying heart disease.
Area of Science:
- Pharmacology
- Cardiology
- Electrophysiology
Background:
- Encainide is a Class IC antiarrhythmic medication.
- It impacts cardiac action potential and refractory periods without significantly affecting heart rate or contractility.
Purpose of the Study:
- To detail the electrophysiological effects of encainide.
- To evaluate its efficacy and safety in treating various cardiac arrhythmias.
- To discuss its metabolic pathways and clinical role.
Main Methods:
- Review of encainide's pharmacological and electrophysiological properties.
- Analysis of its effects on cardiac intervals (AH, PR, QRS, H-V, QT).
- Assessment of its efficacy in premature ventricular complexes (PVCs) and ventricular tachycardia (VT), and supraventricular arrhythmias.
Main Results:
- Encainide decreases the maximum rate of phase 0 depolarization and increases effective refractory periods.
- It increases AH, PR, QRS, and H-V intervals, with QT prolongation secondary to QRS widening.
- Metabolites O-demethyl encainide (ODE) and 3-methoxy-ODE (MODE) share similar pharmacology.
- The drug exhibits minimal negative inotropic effects and is well-tolerated, with side effects like blurred vision and dizziness.
- Effective for PVCs and supraventricular arrhythmias (atrial fibrillation, PSVT, ectopic atrial tachycardia); less effective for sustained VT.
- Proarrhythmia occurs in about 10% of patients, higher in those with VT or underlying heart disease.
Conclusions:
- Encainide is a valuable antiarrhythmic agent for specific supraventricular and ventricular arrhythmias.
- Its predictable electrophysiological effects and generally favorable safety profile support its use.
- Careful patient selection and monitoring are essential due to the risk of proarrhythmia.