Ask the Doctors: Patient worried about anti-arrhythmic drug side affects
A: I can understand your concerns regarding amiodarone; the potential side effects do sound alarming. But keep in mind that the drug has been used for many years to help control the heart from going into abnormal rhythms and, unlike other medications used to maintain normal heart rhythm, amiodarone is less likely to cause abnormal heart rhythms, meaning that it is less likely to lead to sudden cardiac death. Because of this, amiodarone is the most commonly prescribed anti-arrhythmic medication.
That doesn't mean one should discount the possible side effects. First, amiodarone can be toxic to the lungs, causing an inflammatory reaction that leads to cough, shortness of breath, weight loss and chest pain. Lung toxicity occurs 5 to 15 percent of the time at doses higher than 400 milligrams per day, but only 1.9 percent of the time at doses of 150 to 330 milligrams per day. Because amiodarone is stored in fat cells, it may take months for the symptoms to begin to reverse, so afflicted patients will need to take prolonged courses of oral steroids to decrease inflammation.
Amiodarone can also affect the thyroid, causing low or high thyroid levels in the blood. Low thyroid levels are most likely, occurring in up to 20 percent of patients on high doses of the medication, but in only 3 to 4 percent of patients taking lower doses. High thyroid levels can result up to 3 percent of the time. Because of these effects, you should have your thyroid levels checked before starting amiodarone and every six months after starting the medication.
As you mentioned, the drug can also cause nerve dysfunction in the eye, leading to blindness, though this is rare. Amiodarone can also affect other nerves of the body, leading to tremors, loss of sensation and loss of bodily control. This happens much less frequently at lower doses, but still occurs about 4 percent of the time. Further, the drug can elevate blood tests for liver enzymes, with some people developing significant liver inflammation. As with the thyroid, you should monitor your liver function every six months while taking amiodarone.
A host of minor side effects include nausea, skin reactions and urinary difficulties.
You mentioned considering catheter ablation, which is sometimes performed for abnormal heart rhythms. In this procedure, an energy source is used to destroy the portion of the heart causing the abnormal rhythm. However, with some heart rhythm problems, such as atrial fibrillation, catheter ablation may initially convert the rhythm, but after one year the atrial fibrillation returns in up to 60 percent of patients. Using amiodarone before and after the catheter ablation can significantly increase the rate of success for the ablation. So, if you have atrial fibrillation, you may benefit from both amiodarone and catheter ablation.
I'm not certain what type of heart condition you have or why your doctor recommends amiodarone specifically. But it is, indeed, a good medication for preventing abnormal heart rhythms. Just be sure you're monitored closely for lung toxicity, thyroid abnormalities and liver inflammation.
Robert Ashley, M.D., is an internist and assistant professor of medicine at the University of California, Los Angeles. Send your questions to firstname.lastname@example.org, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.
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