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Amiodarone has numerous side effects. Most individuals administered amiodarone on a chronic basis will experience at least one side effect.
Thyroid
Due to the iodine content of the agent (37.3% by weight), abnormalities in thyroid function are common. Amiodarone is structurally similar to thyroxine (a thyroid hormone), which contributes to the effects of amiodarone on thyroid function. The incidence of hypothyroidism is about 6%, while the incidence of hyperthyroidism is about 2%. They are called Wolff-Chaikoff effect and Jodbasedow effect separately.
Measurement of free thyroxine (FT4) alone may be unreliable and thyroid-stimulating hormone (TSH) should therefore also be checked every 6 months.
Thyroid uptake measurements (I-123 or I-131), which are used to differentiate causes of hyperthyroidism, are generally unreliable in patients who have been taking amiodarone. Because of the high iodine content of amiodarone, the thyroid gland is effectively saturated, thus preventing further uptake of isotopes of iodine. However, the radioactive iodine uptake (nuclear thyroid uptake test) may still be helpful in the diagnosis and management of amiodarone-induced hyperthyroidism.
Eye
Corneal micro-deposits (Corneal verticillata, also called vortex keratopathy) are almost universally present (over 90%) in individuals taking amiodarone for at least 6 months. These deposits typically do not cause any symptoms. About 1 in 10 individuals may complain of a blueish halo. Optic neuropathy occurs in 1-2% of people and is not dosage dependent. Bilateral optic disk swelling and mild and reversible visual field defects can also occur.
Gastrointestinal system
Liver toxicity due to amiodarone is quite rare. A drug-induced hepatitis (inflammation of the liver) may occur and is sometimes reversible by lowering the dose.
Skin
Long-term administration of amiodarone is associated with a blue-grey discoloration of the skin, "smurf syndrome." This is more commonly seen in individuals with lighter skin tones. The discoloration may revert upon cessation of the drug. However, the skin color may not return completely to normal.
Individuals taking amiodarone may become more sensitive to the harmful effects of UV-A light. Taking sunblock that also blocks UV-A rays appears to prevent this side effect.
Lung
The most serious reaction that is due to amiodarone is interstitial lung disease. The incidence of pulmonary fibrosis is not dose related. Some individuals were noted to develop pulmonary fibrosis after a week of treatment, while others did not develop it after years of continuous use. There are no known factors that increase the incidence of amiodarone-induced pulmonary fibrosis in a particular individual. Common practice is to avoid the agent if possible in individuals with decreased lung function.
The most specific test of pulmonary toxicity due to amiodarone is a dramatically decreased DLCO noted on pulmonary function testing.
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Important notice:
The content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other
qualified health provider with any questions you may have regarding a medical condition.
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