Side effects
At oral doses of 400 mg per day or higher, amiodarone can have serious, varied side effects, including toxicity to thyroid, liver, lung, and retinal functions, requiring clinical surveillance and regular laboratory testing. Allergic reactions to amiodarone may occur. Most individuals administered amiodarone on a chronic basis will experience at least one side effect. In some people, daily use of amiodarone at 100 mg oral doses can be effective for arrhythmia control with no or minimal side effects. Lung
Side effects of oral amiodarone at doses of 400 mg or higher include various pulmonary effects. The most serious reaction is interstitial lung disease. Risk factors include high cumulative dose, more than 400 milligrams per day, duration over two months, increased age, and preexisting pulmonary disease. Some individuals were noted to develop pulmonary fibrosis after a week of treatment, while others did not develop it after years of continuous use. 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. Thyroid
Induced abnormalities in thyroid function are common. Both under- and overactivity of the thyroid may occur. Amiodarone is structurally similar to thyroxine and  also contains iodine. Both of these contribute to the effects of amiodarone on thyroid function.
Congenital megaesophagus is usually identified when a foal begins to eat solid food from the ground; prior to this, as the foal nurses milk from its mother, the milk passes easily down into the stomach. The most common signs are difficulty swallowing (dysphagia) and inhalational pneumonia. References
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Canine megaesophagus