Oral Flecainide, Sotalol, and Verapamil for the Termination of Paroxysmal Supraventricular Tachycardia

The ability to terminate supraventricular tachycardia (SVT) acutely with an oral dose of flecainide (2.5–3.3 mg/kg). sotalol (2.0–2.9 mg/kg), and verapamil (3.3–3.7 mg/kg) was investigated in an observational study of six patients u'ith SVT normally controlled by an antitachycardia pacemaker. The pacemaker was programmed to induce SVT and the stahility of SVT was observed for 90 minutes as a baseline. Subsequent studies involved testing of the three antiarrhythmic drugs on separate occasions, given in random order as crushed tablets in orange juice during pacemaker induced SVT, with plasma drug levels collected every 15 minutes for 90 minutes post drug ingestion. Sotalol produced drug induced slowing of SVT in all six patients, with termination of SVT in three patients by 60–65 minutes, with maximum plasma levels of 0.76–2.09 μg/mL achieved by 90 minutes. Flecainide produced maximum plasma levels of 83–745 ng/mL, 60–90 minutes post ingestion, and slowed SVT in three patients, SVT was terminated in three patients after 45–85 minutes, but no effect on SVT was seen in two patients who had inodequate plasma levels (≤ 166 ng/mL) from doses < 3 mg/kg. Verapamil produced maximum plasma levels of 0 (undetectable) to 388 ng/mL, 45–90 minutes post ingestion, and slowed SVT in three patients, but only one of these patients reverted to sinus rhythm (at 40 min). No effect on SVT was seen in three patients due to undetecfable plasma levels. We concluded that sotalol (≤ 2 mg/kg) and flecainide (≤ 3 mg/kg) appeared to be suitable oral drugs for termination of SVT. Verapamil appeared unsuitable due to its unpredictable bioavailability, despite the use of high doses (> 3 mg/kg).