Amiodarone also causes an anti-thyroid action, via Wolff–Chaikoff effect, due its large amount of iodine in its molecule, which causes a particular cardiac hypothyroidism with bradycardia and arrhythmia. What this means is that amiodarone may stimulate the thyroid gland to release excessively large quantities of thyroid hormone. This could lead to a serious arrhythmia, among other problems. Amiodarone is a potent antiarrhythmic drug that is used to treat ventricular and supraventricular tachyarrhythmias. It is a benzofuran-derived, iodine-rich compound with some structural similarity to thyroxine (T4). Amiodarone hydrochloride tablets can cause you to have either decreased thyroid function (hypothyroidism), which can sometimes be severe, or an overactive thyroid (hyperthyroidism), which can be severe. What is amiodarone, and how does it work (mechanism of action)? Amiodarone is an oral and injectable drug that is used to correct abnormal rhythms of the heart. (It is an antiarrhythmic medication.) Abstract. Although amiodarone is regarded as a highly effective anti-arrhythmic agent, its use may lead to alterations in thyroid gland function and/or thyroid hormone metabolism, partly because of its rich iodine content. The effect of amiodarone on thyroid metabolism remains unclear but probably involves an intracellular rather than a central or peripheral action. Ellenhorn, M.J., S. Schonwald, G. Ordog, J. Wasserberger. Amiodarone is an antiarrhythmic drug with structural similarities to thyroxine. It exhibits all four of the classic Vaughan Williams mechanisms of action, namely sodium and potassium channel blockade, a mild antisympathetic action and some calcium channel blockade, but it is usually classified as a Class III antiarrhythmic drug (see Table 1). Amiodarone (Cordarone) is a commonly prescribed medication for the management of both atrial and ventricular arrhythmias. Unfortunately, when amiodarone is given to a euthyroid (normal thyroid function) patient , the normal physiologic process for the formation of the thyroid hormones, thyroxine (T4) and 3,5,3'-triiodothyronine (T3), can be. Hermida JS, Jarry G, Tcheng E, et al. Radioiodine ablation of the thyroid to allow the reintroduction of amiodarone treatment in patients with a prior history of amiodarone-induced thyrotoxicosis. Am J Med 2004; 116:345.