Iopanoic acid is an iodine

Iodine

Iodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor....

-containing radiocontrast medium

Radiocontrast

Radiocontrast agents are a type of medical contrast medium used to improve the visibility of internal bodily structures in an X-ray based imaging techniques such as computed tomography or radiography...

 used in cholecystography

Cholecystography

Oral cholecystography is a procedure used to visualize the gallbladder by administering, by mouth, a radiopaque contrast agent that is excreted by the liver. This excreted material will collect in the gallbladder, where reabsorption of water concentrates the excreted contrast...

. Both iopanoic acid and ipodate sodium

Ipodate sodium

Ipodate sodium is an iodine-containing radiopaque contrast media used for X-rays. The drug is given orally and the resulting contrast allows for easy resolution of the bile duct and gall bladder...

 are potent inhibitors of thyroid hormone

Thyroid hormone

The thyroid hormones, thyroxine and triiodothyronine , are tyrosine-based hormones produced by the thyroid gland primarily responsible for regulation of metabolism. An important component in the synthesis of thyroid hormones is iodine. The major form of thyroid hormone in the blood is thyroxine ,...

 release from thyroid gland, as well as of peripheral conversion of thyroxine

Thyroxine

Thyroxine, or 3,5,3',5'-tetraiodothyronine , a form of thyroid hormones, is the major hormone secreted by the follicular cells of the thyroid gland.-Synthesis and regulation:...

 (T₄) to triiodothyronine

Triiodothyronine

Triiodothyronine, C15H12I3NO4, also known as T3, is a thyroid hormone. It affects almost every physiological process in the body, including growth and development, metabolism, body temperature, and heart rate....

 (T₃). These compounds inhibit 5'deiodinase (5'DID-1 and 5'DID-2) enzymes, which catalyse T₄-T₃ conversion in the thyroid cell, liver, kidney, skeletal muscle, heart, brain, pituitary. This accounts for the dramatic improvement in both subjective and objective symptoms of hyperthyroidism

Hyperthyroidism

Hyperthyroidism is the term for overactive tissue within the thyroid gland causing an overproduction of thyroid hormones . Hyperthyroidism is thus a cause of thyrotoxicosis, the clinical condition of increased thyroid hormones in the blood. Hyperthyroidism and thyrotoxicosis are not synonymous...

, particularly when they are used as an adjunctive therapy with thioamide

Thioamide

Thioamide is a functional group with the general structure R-CS-NR'R, where R, R', and R are organic groups. They are analogous to amides but they exhibit greater multiple bond character along the C-N bond, resulting in a larger rotational barrier...

s (propylthiouracil

Propylthiouracil

Propylthiouracil or 6-n-Propylthiouracil is a thioamide drug used to treat hyperthyroidism by decreasing the amount of thyroid hormone produced by the thyroid gland...

, carbimazole

Carbimazole

Carbimazole is used to treat hyperthyroidism. Carbimazole is a pro-drug as after absorption it is converted to the active form, methimazole. Methimazole prevents the thyroid peroxidase enzyme from coupling and iodinating the tyrosine residues on thyroglobulin, hence reducing the production of the...

). These are less toxic, as iodine is covalently bound in these compounds. They can be used in the treatment of patients with severe thyrotoxicosis (thyroid storm) and significant morbidity (e.g., myocardial infarction

Myocardial infarction

Myocardial infarction or acute myocardial infarction , commonly known as a heart attack, results from the interruption of blood supply to a part of the heart, causing heart cells to die...

, or stroke) for rapid control of elevated plasma triiodothyronine concentrations.