Iopanoic acid is an iodine-containing radiocontrast medium used in cholecystography. Both iopanoic acid and ipodate sodium are potent inhibitors of thyroid hormone release from thyroid gland, as well as of peripheral conversion of thyroxine (T₄) to triiodothyronine (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, particularly when they are used as an adjunctive therapy with thioamides (propylthiouracil, carbimazole). They can be used in the treatment of patients with severe thyrotoxicosis (thyroid storm) and significant morbidity (e.g., myocardial infarction, or stroke) for rapid control of elevated plasma triiodothyronine concentrations. The use of iopanoic acid for treatment of thyrotoxicosis has been discontinued in the United States.

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Iopanoic acid

Clinical data
AHFS/Drugs.com	Micromedex Detailed Consumer Information
ATC code	V08AC06 (WHO)
Identifiers
IUPAC name (RS)-2-[(3-Amino-2,4,6-triiodophenyl)methyl]butanoic acid
CAS Number	96-83-3
PubChem CID	3735
DrugBank	DB08946 N
ChemSpider	3604
UNII	FE9794P71J
KEGG	D01014
ChEMBL	ChEMBL867 Y
CompTox Dashboard (EPA)	DTXSID6023159
ECHA InfoCard	100.002.310
Chemical and physical data
Formula	C11H12I3NO2
Molar mass	570.935 g·mol−1
3D model (JSmol)	Interactive image
Melting point	162–163 °C (324–325 °F)
SMILES CCC(CC1=C(C(=C(C=C1I)I)N)I)C(=O)O
InChI InChI=1S/C11H12I3NO2/c1-2-5(11(16)17)3-6-7(12)4-8(13)10(15)9(6)14/h4-5H,2-3,15H2,1H3,(H,16,17) Key:OIRFJRBSRORBCM-UHFFFAOYSA-N

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In addition to inhibiting deiodinase enzymes, iopanoic acid is also a substrate of type 1 deiodinase. Iopanoic acid underwent monodeiodination in the presence of type 1 deiodinase in a microsomal mouse liver preparation.^[1]