Control of paroxysmal atrial fibrillation recurrence using combined administration of propafenone and quinidine

The frequent recurrence of paroxysmal atrial fibrillation (PAF) despite the use of standard antiarrhythmic agents prompted the use of new therapeutic approaches, There are few data on systematic assessment of PAF control with stepwise dose escalation and the use of a drug combination. Low-dose quini dine may promote the efficacy of propafenone by inhibiting its degradation through the cytochrome P450 pathway (CYP2D6), We prescribed propafenone 300 to 450 mg/day to 60 patients with PAF for 8 weeks, and 62% were symptomati cally controlled. The 19 refractory patients were randomized in a double-bl inded fashion to receive either a higher dose of propafenone (450 to 675 mg /day) or the standard dose of propafenone with low-dose quinidine 150 mg/da y, each for an 8-week study period, and subsequently crossed over to the al ternative treatment, The resulting serum propafenone concentrations were 25 9 +/- 208 and 336 +/- 237 mg/day (p >0.5), respectively, Both treatment arm s prolonged the time to the first symptomatic atrial fibrillation (AF) recu rrence and the interval between attacks, and AF was controlled in 37% of pa tients. However, the higher dose of propafenone was associated with gastroi ntestinal side effects not present with the low-dose quinidine combination. Of the 10 refractory patients, 7 were further controlled with a standard d ose of propafenone plus quinidine (600 mg/day). Overall, control of PAF was achieved in 85% of patients at the end of 8 months; adverse effects necess itating withdrawal were observed in 6%, and uncontrolled AF in 5% of patien ts, There was no difference in the mean AF rate during recurrences in all p hases, and ventricular proarrhythmia was not seen. This study documents the role of stepwise antiarrhythmic treatment of PAF, The use of a standard do se of propafenone, followed by low-dose quinidine combination to reduce pro pafenone degradation, and the combined standard dose of propafenone and qui nidine may be used to maximize efficacy and tolerability, (C) 2000 by Excer pta Medica, Inc.