Drug efficacy and pharmacokinetics were assessed in 63 patients, aged 5 days to 30 years (mean 8 years), who received flecainide acetate for control of resistant arrhythmias. Doses of flecainide ranged from 59 to 225 mg/m2 body surface area per day (mean 141) in divided doses every 8 to 12 h and serum trough levels ranged from 0.10 to 0.99 μg/ml (mean 0.36). Flecainide controlled or partially controlled arrhythmia in 53 (84%) of the 63 patients: 7 of 7 patients who had the permanent form of junctional reciprocating tachycardia, 12 of 13 who had an atrial ectopic tachycardia, 10 of 10 who had ventricular tachycardia and 18 of 25 patients who had reentrant supraventricular tachycardia. Five of seven patients who had the latter arrhythmia were unsuccessfully treated with flecainide. They had Wolfl-Parkinson-White syndrome and developed asymptomatic, incessant, slower orthodromic reciprocating tachycardia while receiving the drug. Transient blurred vision was reported in three patients and two patients had transient hyperactivity. No significant hemodynamic side effects were seen in any patient. Twenty-five patients underwent oral pharmacokinetic investigation. Young infants (<1 year of age) had a mean plasma elimination half-life (11/2) approximating that (11 to 12 h) found in older children and healthy adults; children aged I to 12 years had a shorter mean t 1/2 of 8 h. Dosing schedules based on milligrams per square meter body surface area correlated better with plasma flecainide levels than did dosing based on milligrams per kilogram body weight. In conclusion, 1) flecainide was effective pediatric therapy for permanent junctional reciprocating tachycardia, atrial ectopic and chaotic atrial tachycardia, ventricular tachycardia and, in most patients, reentrant supraventricular tachycardia; 2) some patients with WolffParkinson-White syndrome developed asymptomatic incessant slow supraventricular tachycardia while receiving flecainide; 3) flecainide resulted in rare side effects and no negative hemodynamic effects in any patient; 4) despite a shorter elimination half-life, every 12 h dosing schedule (with lower flecainide trough levels than usually seen in adults) provided adequate arrhythmia control in 80% of young patients aged 1 to 12 years; and 5) further study of oral flecainide pharmacokinetics is needed for patients < 1 year of age. © 1989.
Perry, J. C., McQuinn, R. L., Smith, R. T., Gothing, C., Fredell, P., & Garson, A. (1989). Flecainide acetate for resistant arrhythmias in the young: Efficacy and pharmacokinetics. Journal of the American College of Cardiology, 14(1), 185–191. https://doi.org/10.1016/0735-1097(89)90070-3