Amiodarone Rifampicin Drug–Drug Interaction Management With Therapeutic Drug Monitoring

The authors present a case of a 69-year-old man with arrhythmogenic right ventricular cardiomyopathy controlled with amiodarone and an infected orthopedic prosthesis requiring treatment with rifampicin. This combination involves a pharmacokinetic drug-drug interaction leading to subtherapeutic drug concentrations of amiodarone and its active metabolite. The long half-life of amiodarone and its active metabolite in combination with the late onset and offset of cytochrome P4503A (CYP3A4) induction by rifampicin makes this a challenging drug-drug interaction to cope with in clinical practice. Before, during, and after rifampicin treatment, the serum concentrations of amiodarone and its active metabolite were measured and the amiodarone dose was adjusted accordingly. The amiodarone dose required to maintain effective concentrations was 450% of the initial dose. The drug-drug interaction between amiodarone and rifampicin is relevant, both clinically and pharmacokinetically, and can be managed by dose adjustments of amiodarone based on serum concentrations.