Dosing recommendations for encainide.
The onset of antiarrhythmic action of encainide in patients with ventricular arrhythmias occurred within 3 hours after a single dose of 25 or 50 mg. No significant antiarrhythmic activity was noted after only 10 mg. After 14 days of daily dosing, both the 25- and 50-mg dose levels of encainide administered 3 times/day abolished or decreased ventricular arrhythmias in patients tested over a 24-hour period, whereas the 10-mg dose was ineffective. In 5 well-controlled studies involving 331 patients, encainide produced a dose-related decrease in the absolute number of ventricular arrhythmias as well as an increase in the percentage of responders (greater than 75% decrease in ventricular arrhythmias). Doses of 75 mg/day were required to obtain at least a 50% reduction in ventricular arrhythmias or 50% of patients responding or both. Three-times-a-day dosing was as effective as 4-times-a-day dosing. Further, doses greater than 200 mg/day gave little or no increase in incidence of efficacy. Important side effects were very low using doses of less than or equal to 150 mg/day and increased significantly at greater than or equal to 150 mg/day. It is recommended that encainide be initiated at 25 mg 3 times/day for 4 to 7 days, then carefully titrated upward, as needed, to 35 and 50 mg 3 times/day, respectively, every 4 to 7 days. If needed, 50 mg 4 times/day is an appropriate next dosage. Rapid dose escalation or doses greater than 200 mg are discouraged. Patients with severe life-threatening arrhythmias should receive encainide in a setting with cardiac monitoring and advanced life support systems.
D000813:Anilides / Q000008:administration & dosage* / Q000009:adverse effects / Q000097:blood / Q000627:therapeutic use; D001145:Arrhythmias, Cardiac / Q000188:drug therapy; D002986:Clinical Trials as Topic; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D004334:Drug Administration Schedule; D016700:Encainide / Q000031:analogs & derivatives; D006352:Heart Ventricles; D006801:Humans; D007700:Kinetics; D011897:Random Allocation
D000813:Anilides; C033635:O-demethylencainide; C033636:3-methoxy-O-demethylencainide; D016700:Encainide