Amiodarone is a medication prescribed to treat life-threatening ventricular arrhythmias (irregular heartbeats that originate in the ventricle or lower chamber of the heart). Amiodarone works by relaxing the muscles of the heart and suppressing the flow of potassium across membranes, which changes the electrical impulses, therefore, slowing down the rate of contraction. Although it has shown to be effective in treating all types of arrhythmias, because of its effects on other parts of the body, it is usually only prescribed when other medications fail to control the irregular heartbeat.
Lung Damage
Amiodarone has a long half-life (the amount of time it takes to completely break-down in the body); more than 30 days as reported by an article published in "Chest." This contributes to its toxic effects in the body because it makes it difficult to monitor the amount of drug at any given time. In addition, although amiodarone acts on the functions of the heart, the metabolites (compounds it breaks down into within the body) accumulate in the tissues of the lungs.
The excessive amount of drug in the lungs can cause a variety of changes within the lungs. Pulmonary fibrosis, which is the build-up of scar tissue in the lungs, is linked to long-term treatment with amiodarone. Amiodarone may also cause acute pulmonary toxicity, or lung damage, that results in inflammation of the lung tissue, which reduces the amount of oxygen the lungs can absorb.
Liver Damage
The liver is the organ in the body responsible for filtering the blood to break down nutrients. It also breaks down the drugs we take to clear them from the body. Because amiodarone has such a long half-life, it is continually presented to the liver, which can result in toxicity.
Treatment with even low doses of amiodarone is known to cause liver damage similar to the damage caused by excessive alcohol use. Approximately 25 percent of all patients on long-term amiodarone treatment experience an increase in liver enzymes according to information published in "Age and Aging." This increase in liver enzymes can indicate liver damage that can lead to cirrhosis of the liver, which is the build-up of scar tissue that can block blood flow through the liver, interfering with normal liver functions.
Thyroid Dysfunction
The chemical structure of amiodarone is similar to that of the thyroid hormone T4, also known as thyroxine. In addition amiodarone consists of 37 percent iodine by weight according to an article published in "Critical Care Nurse." This contributes to why amiodarone increases the production of T4, but inhibits its ability to transform into T3, triiodothyronine resulting in hypothyroidism or a low level of thyroid hormones. Patients suffering from hypothyroidism may feel tired, sluggish, constipated, depressed and experience weight gain.
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