Systematic (IUPAC) name
Clinical data
AHFS/ monograph
MedlinePlus a682464
Pregnancy cat. D (US)
Legal status -only (US)
Routes Oral
Pharmacokinetic data
Bioavailability 93%
Protein binding None
Metabolism Hepatic
Half-life 5-6 hours
Excretion Renal
CAS number 60-56-0 YesY
ATC code H03BB02
PubChem CID 1349907
DrugBank APRD00002
ChemSpider 1131173 YesY
UNII 554Z48XN5E YesY
KEGG D00401 YesY
ChEBI CHEBI:50673 YesY
Chemical data
Formula C4H6N2S 
Mol. mass 114.17 g/mol
SMILES eMolecules & PubChem
Physical data
Melt. point 146 °C (295 °F)
Solubility in water 2.75 mg/mL (20 °C)
 N(what is this?)  (verify)

Methimazole (also known as Tapazole or Thiamazole or MMI) is an antithyroid drug[1], and part of the thioamide group.



Methimazole is a drug used to treat hyperthyroidism, a condition that usually occurs when the thyroid gland is producing too much thyroid hormone. It may also be taken before thyroid surgery to lower thyroid hormone levels and minimize the effects of thyroid manipulation.

Mechanism of action

Methimazole inhibits the addition of iodine to thyroglobulin by the enzyme thyroperoxidase, a necessary step in the synthesis of triiodothyronine (T3) and thyroxine (T4).

It does not inhibit the action of the sodium-dependent iodide transporter located on follicular cells' basolateral membranes. Inhibition of this step requires competitive inhibitors such as perchlorate and thiocyanate.

It acts at CXCL10.[2]

Adverse effects

It is important to monitor any symptoms of fever or sore throat while taking methimazole; this could indicate the development of agranulocytosis, an uncommon but severe side effect resulting from a drop in the white blood cell count (to be specific, neutropenia, a deficiency of neutrophils). A complete blood count (CBC) with differential is performed to confirm the suspicion, in which case the drug is discontinued. Administration of recombinant human granulocyte colony-stimulating factor (rhG-CSF) may increase recovery.

Other side effects include

  • skin rash
  • itching
  • abnormal hair loss
  • upset stomach
  • vomiting
  • loss of taste
  • abnormal sensations (tingling, prickling, burning, tightness, and pulling)
  • swelling
  • joint and muscle pain
  • drowsiness
  • dizziness
  • decreased white blood cells
  • decreased platelet
  • Aplasia cutis congenita (prenatal exposure)

Drug interactions

Adverse effects may occur for individuals who:

  • Take anticoagulants ('blood thinners') such as warfarin (Coumadin), diabetes medications, digoxin (Lanoxin), theophylline (Theobid, Theo-Dur), and vitamins
  • Have ever had any blood disease, such as decreased white blood cells (leukopenia), decreased platelets (thrombocytopenia), or aplastic anemia, or liver disease (hepatitis, jaundice)
  • Are pregnant, or going to become pregnant, or are breast-feeding. An alternative anti-thyroid drug, propylthiouracil, is often substituted during pregnancy or breast-feeding. If pregnancy occurs while taking methimazole, switching to propylthiouracil may be an alternative. Early studies suggested that methimazole may harm the fetus; however, more recent studies suggest this may not be the case.[citation needed]
  • Are going to have surgery, including dental surgery.

See also


  1. ^ Nakamura H, Noh JY, Itoh K, Fukata S, Miyauchi A, Hamada N (June 2007). "Comparison of methimazole and propylthiouracil in patients with hyperthyroidism caused by Graves' disease". The Journal of clinical endocrinology and metabolism 92 (6): 2157–62. doi:10.1210/jc.2006-2135. PMID 17389704. 
  2. ^ Crescioli C, Cosmi L, Borgogni E, et al. (October 2007). "Methimazole inhibits CXC chemokine ligand 10 secretion in human thyrocytes". J. Endocrinol. 195 (1): 145–55. doi:10.1677/JOE-07-0240. PMID 17911406. 

Wikimedia Foundation. 2010.

Look at other dictionaries:

  • methimazole — /me thim euh zohl , thuy meuh /, n. Pharm. a white crystalline substance, C4H6N2S, that inhibits thyroxin synthesis, used in the treatment of hyperthyroidism. [METH(YL) + IM(ID)AZOLE] * * * …   Universalium

  • methimazole — noun A thioamide drug, 1 methyl 3H imidazole 2 thione, used to treat hyperthyroidism …   Wiktionary

  • methimazole — An antithyroid drug similar in action to propylthiouracil. * * * me·thi·ma·zole me thī mə .zōl, mə n a drug C4H6N2S used to inhibit activity of the thyroid gland * * * meth·im·a·zole (meth imґə zōl) [USP] a thyroid inhibitor, used in… …   Medical dictionary

  • methimazole — me·thi·ma·zole …   English syllables

  • methimazole — n.; see carbimazole …   The new mediacal dictionary

  • methimazole — meˈthīməˌzōl, məˈ noun ( s) Etymology: methyl + imidazole : a drug C4H6N2S used to inhibit activity of the thyroid gland …   Useful english dictionary

  • Hyperthyroidism — Classification and external resources Triiodothyronine (T3, pictured) and thyroxine (T4) are both forms of thyroid hormone. ICD 10 …   Wikipedia

  • Carbimazole — Systematic (IUPAC) name ethyl 3 methyl 2 sulfanylidene imidazole 1 carboxylate Clinical data Trade names Neo mercazole …   Wikipedia

  • Thioamide — (rarely, thionamide) 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 except that they exhibit greater multiple bond character between the C N bond. One of the best… …   Wikipedia

  • Liste Des Maladies Rares — Liste des maladies commençant par une lettre Mise en garde médicale Maladie rare Liste des maladies rares Commençant par un chiffre Commençant par une lettre …   Wikipédia en Français

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.