Carbimazole

Carbimazole
Carbimazole
Systematic (IUPAC) name
ethyl 3-methyl-2-sulfanylidene-imidazole-1-carboxylate
Clinical data
Trade names Neo-mercazole
AHFS/Drugs.com International Drug Names
Pregnancy cat.  ?
Legal status Prescription only
Routes oral
Pharmacokinetic data
Protein binding 85%
Identifiers
CAS number 22232-54-8
ATC code H03BB01
PubChem CID 31072
DrugBank APRD00503
ChemSpider 28829 YesY
UNII 8KQ660G60G YesY
KEGG D07616 YesY
ChEBI CHEBI:617099 YesY
ChEMBL CHEMBL508102 YesY
Chemical data
Formula C7H10N2O2S 
Mol. mass 186.233 g/mol
SMILES eMolecules & PubChem
 YesY(what is this?)  (verify)

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 thyroid hormones T3 and T4 (thyroxine).

Contents

Clinical use

Therapy for hyperthyroidism generally starts at a high daily dose of 15 - 40mg continued until the patient has normal thyroid function, and then reduced to a maintenance dose of 5 - 15mg. Treatment is usually given for 12 - 18 months followed by a trial withdraw.

The onset of anti-thyroid effect is rapid but the onset of clinical effects on thyroid hormone levels in the blood is much slower. This is because the large store of pre-formed T3 and T4 in the thyroid gland and bound to Thyroid Binding Globulin (99% bound) has to be depleted before any beneficial clinical effect occurs.

Precautions

Some people are allergic to azole(s).

Some azole drugs have adverse side-effects.

Some azole drugs may disrupt estrogen production in pregnancy, affecting pregnancy outcome. [1]

Side Effects

Whilst rashes and pruritus are common, these can often be treated with antihistamines without stopping the carbimazole. For those patients where sensitivity reactions can not be controlled, propylthiouracil may be used as an alternative.

Its most serious rare side effect is bone marrow suppression causing neutropenia and agranulocytosis. This may occur at any stage during treatment and without warning. Patients are advised to immediately report symptoms of infection, especially sore throats, so that a full blood count test may be arranged. If this confirms a low neutrophil count then the drug must be discontinued immediately, allowing for usually a prompt recovery. However failure to report suggestive symptoms or delays in considering the possibility of immunosuppression and its testing, can lead to fatalities. Should be used with caution in pregnancy as crosses the placenta barrier.


Brand names

  • Neomercazole
  • Vidalta
  • Camazol

See also

References