Indecainide, a new antiarrhythmic agent classified as type Ic was evaluated in 11 patients with
heart disease who had greater than or equal to 30
ventricular premature complexes/hour, moderate-to-marked
left ventricular dysfunction, and mean ejection fraction 34% +/- 8%. Patients received
indecainide, 50 mg by mouth, every 6 hours and the dose was increased until greater than or equal to 80% suppression was noted, adverse effects occurred, or a maximum dose of 100 mg
indecainide was given every 6 hours.
Ventricular premature complexes were suppressed greater than or equal to 80% in nine patients (p less than 0.05) and
ventricular tachycardia episodes were completely suppressed in five of eight patients. The effective or maximal mean daily
indecainide dose was 191 +/- 32 mg; half of the responders achieved achieved efficacy at serum
drug concentration greater than or equal to 600 ng/ml. Serum
drug concentration was directly related to gender (r = 0.78, p less than 0.04) and inversely related to
creatinine clearance (r = 0.74, p less than 0.05) and ejection fraction (r = 0.71, p less than 0.02).
Indecainide prolonged mean PR and QRS intervals (p less than 0.05) but not QT or QTc. There was a linear relation between percent change in PR (r = 0.80, p less than 0.001) and QRS (r = 0.66, p less than 0.001) intervals and serum
drug concentration. After starting or increasing the dose, careful observation of patients with decreased renal function or reduced ejection fraction should be exercised because they attain higher
drug concentration than normal subjects.