Use of oral verapamil in long-term treatment of neonatal, paroxysmal supraventricular tachycardia. A pharmacokinetic study.

Efficacy and pharmacokinetics of verapamil were studied in two neonates affected by supraventricular paroxysmal tachycardia, under maintenance treatment with the drug. Verapamil proved to be fully effective in suppressing arrhythmic episodes at the daily doses of 1.5 mg/kg four times a day in case 1 and of 2 mg/kg in case 2. The results of plasma half-life of the drug, calculated in a dose interval, were 3.14 hr and 2.10 hr, respectively. In patient 2, doses less than 0.95 mg/kg four times a day did not produce detectable drug plasma levels, while a further stepwise increase of dose up to 2 mg/kg four times a day produced a steep rise in trough concentration. So, in view of this dose-concentration relationship, caution is recommended in adjusting verapamil oral dosage.