Digoxin toxicity associated with amiodarone therapy in children.

The addition of amiodarone to digoxin therapy in nine children caused a sharp increase in digoxin serum concentrations (68% to 800%) in the presence of preserved serum creatinine and BUN concentrations. Digoxin half-life was prolonged. Digoxin accumulation could be attributed in part to the decrease in the renal clearance of digoxin resulting from inhibited tubular secretion of the drug and to the reduction in the distribution volume of digoxin caused by amiodarone. Creatinine clearance was not affected by amiodarone. This interaction appears to be more acute in children than in adults, presumably because of the more important role of the renal tubular secretion of digoxin in children. Whenever digoxin and amiodarone therapy are combined, the digoxin serum concentration should be monitored carefully, with appropriate reduction of the digoxin dose.