Amiodarone is not the favorite drug in my formulary in spite of the fact that I have been on it three times for durations of 3-6 months. It is an interesting and extremely dangerous drug. When initially developed and undergoing human testing, mainly at the VA, the testing was stopped because it was so effective in controlling ventricular arrhythmias. It was then approved by the FDA for use. It took several years to discover it bad side effects. The most serious is pulmonary fibrosis, which is almost completely fatal. It can cause both hypothyroidism and hyperthyroidism, both of which are difficult to treat medically once they occur. A very disconcerting side effect is bluish discoloration of the skin, mainly of the nose.
Amiodarone today carries a ?Black Box? warning from the FDA. It is approved ONLY for life threatening ventricular arrhythmias not controlled by any other means. However, it is used extensively by cardiologists for atrial arrhythmias as an ?off label drug?. Why is such a dangerous drug used? Because it is so effective!! It gets the complaining patient and difficult medical problem off of the doctor?s back.
Ordinary PFTs (pulmonary function tests) do not detect the onset of pulmonary fibrosis. The only test that does is a carbon monoxide diffusion test, which is not a routine part of PFTs. An abnormality of change in the baseline is an indicator of fibrosis, but the disease may be irreversible by then.
Taking amiodarone significantly complicates the process of being placed on another anti-arrhythmic drug. It also affects the INR for long periods of time.
Why all of these problems? While we know the mechanism of its action, we have very little idea as to its distribution and metabolism in the body. Its half-life (the time it takes for half of the drug to be gone) is unknown. It is estimated to be between several months and a year. Thus when you stop the drug its effects persist, often fluctuating, for a long time. Thus when first getting on the drug it is difficult to predict the time it takes to raise the INR, and when getting off the drug it may take a long period of time to achieve a stable warfarin dosage. In my own case, I can be 3.0 one day, 4.6 the next day, and 2.2 the third day, all on the same dosage of warfarin.
My advice is that if choosing between amiodarone or flecanide with complications, I would elect for atrial ablation.