Electrocardiographic and antiarrhythmic effects of intravenous amiodarone: results of a prospective, placebo-controlled study

Disorders of the normal, synchronous contraction of the heart (arrhythmias) are a relatively common postoperative occurrence among patients who have undergone cardiac surgery. One drug that has been used to treat cardiac arrhythmias is amiodarone, a compound thought to have several different mechanisms of action for arrythmia inhibition. Previous reports have demonstrated that long time intervals are necessary for achieving maximal effectiveness with oral administration of amiodarone; periods ranging from 7 to 20 days are not uncommon. This is thought to reflect the protracted time needed to attain sufficient blood levels of the drug with oral dosing. To investigate the utility of intravenous administration, 77 patients who had undergone coronary artery bypass grafting surgery (CABG; surgical grafting of healthy vessels to bypass occluded coronary arteries) were given either a placebo injection or intravenous amiodarone for four days following surgery. An initial loading dose (300 milligrams) of amiodarone was followed by maintenance doses (1,200 milligrams every 24 hours for two day, followed by 900 milligrams every 24 hours for two more days). Drug administration resulted in a significant reduction in the incidence of several types of arrythmia. Intravenous amiodarone treatment was stopped in two patients because of side effects. No detrimental hemodynamic (blood pressure-related) effects were observed; there was a mild slowing of the heart rate in the amiodarone-treated patients. (Consumer Summary produced by Reliance Medical Information, Inc.)