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Carbimazole oral

Updated 2 Feb 2023 | Antithyroid drugs


Tablets containing carbimazole.

Drugs List

  • carbimazole 10mg tablets
  • carbimazole 15mg tablets
  • carbimazole 20mg tablets
  • carbimazole 5mg tablets
  • Therapeutic Indications





    Initial dose: 15mg to 60mg daily in two or three divided doses. Continue this dose until the patient becomes euthyroid, usually after 4 to 8 weeks.

    Subsequent therapy may be administered in one of two ways:
    Maintenance regimen:
    Maintenance dose: 5mg to 15mg daily.
    Continue therapy for at least six months, up to eighteen months maximum.

    Blocking-replacement regimen:
    Maintenance dose: 20mg to 60mg daily.
    Supplemental levothyroxine is given concurrently at a dose of 50micrograms to 150micrograms daily, to prevent hypothyroidism. Continue therapy for at least six months, up to eighteen months maximum.


    Initial dose: 15mg daily until euthyroid, then adjust as necessary.
    Higher doses may be required, particularly in thyrotoxic crisis.

    The following alternative dosing schedule may be suitable:
    Children aged 12 years to 18 years
    30mg in single or divided doses until euthyroid, then gradually reduce to a maintenance dose of 30% to 60% of the initial dose.

    Children aged 1 month to 12 years
    750 micrograms per kg (maximum dose 30mg) daily in single or divided doses until euthyroid, then gradually reduce to a maintenance dose of 30% to 60% of initial dose.


    750 micrograms/kg daily in single or divided doses until euthyroid, then gradually reduce to 30% to 60% of initial dose. 1 mg/kg daily may be required, particularly in thyrotoxic crisis.


    Severe haematological disorder
    Severe hepatic impairment

    Precautions and Warnings

    Females of childbearing potential
    Glucose-galactose malabsorption syndrome
    Lactose intolerance
    Mild hepatic impairment
    Retrosternal goitre

    Discontinue treatment temporarily at time of administration of radio-iodine
    Contains lactose
    Monitor creatine kinase levels in patients reporting myalgia
    Monitor for signs of bone marrow depression
    Monitor thyroid function regularly and adjust dose accordingly
    Perform white blood cell count if clinical evidence of infection
    Advise patient to report unexplained fever, sore throat, bruising, bleeding
    Advise patients to report signs of hepatic damage (malaise, jaundice etc.)
    Discontinue permanently if acute pancreatitis occurs
    Discontinue if evidence of significant bone marrow depression
    Discontinue if jaundice or other evidence of hepatic impairment occurs
    Discontinue if liver function tests become abnormal
    Female: Ensure adequate contraception during treatment

    Use with caution in patients with retrosternal goitre as carbimazole may exacerbate this condition and tracheal obstruction may occur.

    Pregnancy and Lactation


    Use carbimazole with caution in pregnancy.

    Manufactures advise that the dose of carbimazole must be regulated by the patient's clinical condition. The lowest dose possible should be used, and this can often be discontinued three to four weeks before term, in order to reduce the risk of neonatal complications. The blocking-replacement regimen should not be used during pregnancy since very little thyroxine crosses the placenta in the third trimester.

    Carbimazole crosses the placenta but, provided the mother's dose is within the standard range and her thyroid status is monitored, there is no evidence of neonatal thyroid abnormalities. Studies have shown that the incidence of congenital malformations is greater in the children of mothers whose hyperthyroidism has remained untreated than in those to whom treatment with carbimazole has been given. However, treatment with carbimazole has been associated with congenital malformations, particularly during the first trimester and at high doses (15mg daily or more).

    The use of carbimazole during pregnancy should be reserved for situations in which a definite therapy of the underlying disease (thyroidectomy or radioiodine treatment) was not suitable prior to pregnancy and in case of new occurrence or recurrence during pregnancy.

    Carbimazole should only be given when treatment with propylthiouracil is not suitable.


    Use carbimazole with caution during brestfeeding.

    The manufacturers recommend that if treatment is continued during lactation, the patient should discontinue breastfeeding.

    Carbimazole is secreted in breast milk.

    Briggs suggest that breastfeeding may continue provided neonatal development is closely monitored and the lowest effective dose is used.


    Advise patient to tell doctor immediately if sore throat, mouth ulcers, bruising or bleeding, fever, malaise or non-specific illness develops.

    Advise patient to report any symptoms of hepatic disorder including upper abdominal pain, anorexia or general pruritis.

    Advise patients of childbearing potential that effective contraceptive measures should be used.

    Side Effects

    Abnormal liver function tests
    Acute pancreatitis
    Airway obstruction
    Aplastic anaemia
    Bone marrow depression
    Cholestatic hepatitis
    Cholestatic jaundice
    Cutaneous vasculitis
    Gastric discomfort
    Haemolytic anaemia
    Hair loss
    Hepatic disorders
    Hypersensitivity reactions
    Insulin autoimmune syndrome
    Mouth ulcers
    Salivary gland enlargement
    Sore throat
    Stevens-Johnson syndrome
    Taste loss


    It is strongly recommended that the UK National Poisons Information Service be consulted on cases of suspected or actual overdose where there is doubt over the degree of risk or about appropriate management.

    The following number will direct the caller to the relevant local centre (0844) 892 0111

    Information may be obtained if you have access to ToxBase the primary clinical toxicology database of the National Poisons Information Service. This is available via password on the internet ( ) or if this is unavailable at the backup site ( ).

    Further Information

    Last Full Review Date: April 2018

    Reference Sources

    Drugs in Pregnancy and Lactation: A Reference Guide to Fetal and Neonatal Risk, 10th edition (2015) ed. Briggs, G., Freeman, R. Wolters Kluwer Health, Philadelphia.

    Summary of Product Characteristics: Carbimazole 5mg Tablets. Concordia International. Revised July 2014.

    Summary of Product Characteristics: Carbimazole 20mg Tablets. Concordia International. Revised July 2014.

    Summary of Product Characteristics: Carbimazole 10mg Tablets. Macleods Pharma UK Ltd. Revised December 2017.

    Summary of Product Characteristics: Carbimazole 15mg Tablets. Macleods Pharma UK Ltd. Revised December 2017.

    HPRA Safety Notice
    Available at:
    Last accessed: 21 January 2019

    MHRA Drug Safety Update February 2019
    Available at:
    Last accessed: 22 February 2019

    NICE - Evidence Services
    Available at:
    Last accessed: 03 April 2018

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