CLINICAL ELECTROPHYSIOLOGIC EFFECTS OF A SINGLE HIGH ORAL DOSE OF AMIODARONE

Several recent reports have described the antiarrhythmic effects of a single high oral dose of amiodarone but clinical electrophysiologic ef fects have not been reported. The present study was performed to asses s electrophysiologic effects in 12 patients. After baseline electrophy siologic studies (EPS) patients were administered a single oral dose o f 30 mg/kg of amiodarone. EPS was repeated 7.5 +/- 0.5 hours later. Pl asma levels of amiodarone and its metabolite desethylamiodarone were d etermined at the time of the second EPS. Holter monitoring was perform ed for 24 hours after amiodarone administration. Amiodarone significan tly increased the following parameters: corrected QT interval (+4.5%), functional refractory period of the right atrium (+7%); AH interval ( +12.3%), effective refractory period of the atrioventricular node (+18 .5%), and cycle length of Wenckebach block (+8.4%). These effects were not correlated with plasma levels of amiodarone and desethylamiodaron e. Holter monitoring detected no significant bradycardia or arrhythmia . These findings indicate that the effects of a single high oral dose of amiodarone are the same as those known to be induced by acute intra venous administration.