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Amiodarone is a class III anti-arrhythmic for tachyarrhythmias
Although most patients remain euthyroid on amiodarone, 4-18% develop thyroid disease months to years after exposure.
Amiodarone-induced thyroid disease occurs because amiodarone is structurally similar to triiodothyronine and thyroxine and each 200mg tablet contains 75 mg of iodine.
Two types of amiodarone-induced thyroid disease:
- Amiodarone-induced hypothyroidism (AIH)
- Amiodarone-induced thyrotoxicosis (AIT)
Amiodarone-induced hypothyroidism (AIH)
- Presents with subtle to overt hypothyroidism
- Treat by discontinuing amiodarone; thyroid recovers within 3 months
- If amiodarone cannot be discontinued, start levothyroxine
Amiodarone-induced thyrotoxicosis (AIT)
- Sudden symptom onset months to years following exposure; mean 2-47 months post-exposure
- Can be a life-threatening presentation (similar to thyroid storm) with severe cardiac manifestations and hemodynamic instability
- Treatment (treat like thyroid storm, if severe)
- Discontinue drug, if possible
- Thionamides (inhibit enzyme producing thyroid hormones)
- Methimazole or propylthiouracil
- Beta-blockers
- Steroids
- Airway and hemodynamic support
References
Padmanabhan H. Amiodarone and Thyroid Dysfunction. South Med J. 2010 Sep; 103 (9): 922-30
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