From the FDA Drug Label
Amiodarone hydrochloride can cause either hypothyroidism (reported in up to 10% of patients) or hyperthyroidism (occurring in about 2% of patients). Monitor thyroid function prior to treatment and periodically thereafter, particularly in elderly patients, and in any patient with a history of thyroid nodules, goiter, or other thyroid disfunction. Hyperthyroidism mayinduce arrhythmia breakthrough If any new signs of arrhythmia appear, the possibility of hyperthyroidism should be considered. Antithyroid drugs, β-adrenergic blockers, temporary corticosteroid therapy may be necessary to treat the symptoms of hyperthyroidism.
To manage a thyroid storm in a patient on Amiodarone, consider the following steps:
- Monitor thyroid function closely
- Use antithyroid drugs, β-adrenergic blockers, and temporary corticosteroid therapy as needed to treat symptoms of hyperthyroidism
- Be aware that radioactive iodine therapy is contraindicated due to low radioiodine uptake associated with Amiodarone-induced hyperthyroidism 1
From the Research
Managing a thyroid storm in a patient on amiodarone requires prompt, aggressive treatment while addressing the unique challenges posed by amiodarone-induced thyrotoxicosis. First, stabilize the patient with supportive care including IV fluids, cooling measures, and oxygen as needed. Administer propylthiouracil (PTU) 600-1000 mg loading dose followed by 200-300 mg every 6 hours to block new thyroid hormone synthesis, as suggested by 2. Since amiodarone contains iodine and has a long half-life, higher doses of antithyroid medications may be needed. Add propranolol 60-80 mg orally every 4-6 hours or IV esmolol/labetalol for severe cases to control adrenergic symptoms. Administer hydrocortisone 100 mg IV every 8 hours to block peripheral conversion of T4 to T3 and support potential adrenal insufficiency. Consider cholestyramine 4 g orally 4 times daily to enhance thyroid hormone elimination. Potassium iodide should be avoided as it's ineffective in amiodarone-induced thyrotoxicosis, as noted in 3. Discontinue amiodarone if possible, though its effects may persist for months due to its long half-life. Monitor cardiac rhythm closely as both the thyroid storm and medication changes can affect arrhythmia control. In severe cases refractory to medical management, plasmapheresis, therapeutic plasma exchange, or emergency thyroidectomy may be necessary, as reported in 2. Endocrinology and cardiology consultation is essential to balance thyroid management with cardiac rhythm control.
Some key points to consider:
- Amiodarone-induced thyroid dysfunction occurs in 15-20% of amiodarone-treated patients, as stated in 3.
- Amiodarone-induced hypothyroidism is easily controlled by L-thyroxine replacement, whereas amiodarone-induced thyrotoxicosis requires more complex management, including thionamides, beta blockers, and corticosteroids, as discussed in 4.
- The high iodine content and prolonged biological half-life of amiodarone can result in thyroid dysfunction, even after cessation of the drug, as mentioned in 5.
- Regular monitoring of thyroid function is crucial in patients taking amiodarone, as recommended in 6.
In terms of treatment, the most recent and highest quality study 2 suggests that plasmapheresis can be an effective treatment option for amiodarone-induced thyroid storm. Therefore, plasmapheresis should be considered in severe cases refractory to medical management. Additionally, endocrinology and cardiology consultation is essential to balance thyroid management with cardiac rhythm control, as both the thyroid storm and medication changes can affect arrhythmia control.