A 69-year-old man with heart failure and paroxysmal atrial fibrillation is prescribed amiodarone for maintenance of sinus rhythm. Which of the following is a known characteristic of amiodarone?

With prolonged treatment, the active N-desethyl derivative of amiodarone accumulates in plasma, and its concentration may exceed that of the parent compound. Amiodarone is poorly (approximately 30%) absorbed and there is marked interindividual variability. The half-life is long, 25-60 days, presumably because it is extensively bound to tissues, resulting in a large volume of distribution and a reservoir of drug. Complicating the use of amiodarone is multiple drug interactions and toxicities including liver, thyroid, and lung.