Which of the following is a major long-term adverse effect associated with amiodarone?

• A. Hypotension
• B. Thyroid dysfunction
• C. Hyperglycemia
• D. Nausea

Answer: (B)

Long-term amiodarone toxicity is dominated by thyroid dysfunction because the drug carries a very large iodine load and remains in the body for a long time. Amiodarone’s iodine content means each dose delivers a substantial amount of iodine to the thyroid, which can overwhelm normal hormone production. This can lead to hypothyroidism in many patients, due to the Wolff-Chaikoff effect where the thyroid temporarily downregulates hormone synthesis in response to excess iodine and may fail to escape. It can also cause thyrotoxicosis in susceptible individuals, either by providing excess iodine to autonomous thyroid tissue (type I) or by a destructive thyroiditis releasing preformed hormone (type II). The combination of high iodine exposure and the drug’s very long tissue half-life means thyroid problems can develop slowly and persist long after stopping the medication. While hypotension, nausea, and other effects can occur, they do not represent the major chronic toxicity that thyroid dysfunction does.