Impact of rifampin on serum amiodarone concentrations in a patient with congenital heart disease

A 33-year-old woman with congenital heart disease and atrial and ventricula r arrhythmias, managed over the long term with an implantable cardioverter defibrillator, epicardial pacing system, and amiodarone, experienced an inc rease in palpitations and a shock from her defibrillator. Evaluation reveal ed decreases in amiodarone and desethylamiodarone serum concentrations from previous levels. Rifampin had been added to her therapy 5 weeks earlier. I ncreases in amiodarone and desethylamiodarone concentrations were observed after an increase in the amiodarone dosage and discontinuation of rifampin. The time course suggested that the addition of rifampin led to reductions in serum concentrations of both the drug and metabolite.