Carbimazole oral
- Drugs List
- Therapeutic Indications
- Dosage
- Contraindications
- Precautions and Warnings
- Pregnancy and Lactation
- Side Effects
- Monograph
Presentation
Tablets containing carbimazole.
Drugs List
Therapeutic Indications
Uses
Hyperthyroidism
Dosage
Adults
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.
Children
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.
Neonates
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.
Contraindications
Galactosaemia
Severe haematological disorder
Severe hepatic impairment
Precautions and Warnings
Females of childbearing potential
Breastfeeding
Glucose-galactose malabsorption syndrome
Lactose intolerance
Mild hepatic impairment
Pregnancy
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
Pregnancy
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.
Lactation
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.
Counselling
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
Agranulocytosis
Airway obstruction
Angioedema
Aplastic anaemia
Arthralgia
Bleeding
Bone marrow depression
Bruising
Cholestatic hepatitis
Cholestatic jaundice
Cutaneous vasculitis
Eosinophilia
Fever
Gastric discomfort
Haemolytic anaemia
Hair loss
Headache
Hepatic disorders
Hepatitis
Hypersensitivity reactions
Insulin autoimmune syndrome
Jaundice
Leucopenia
Lymphadenopathy
Malaise
Mouth ulcers
Myalgia
Myopathy
Nausea
Neuritis
Neutropenia
Pancytopenia
Polyneuropathy
Pruritus
Rash
Salivary gland enlargement
Sore throat
Stevens-Johnson syndrome
Taste loss
Thrombocytopenia
Urticaria
Overdosage
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 ( www.toxbase.org ) or if this is unavailable at the backup site ( www.toxbasebackup.org ).
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: https://www.hpra.ie
Last accessed: 21 January 2019
MHRA Drug Safety Update February 2019
Available at: https://www.mhra.gov.uk
Last accessed: 22 February 2019
NICE - Evidence Services
Available at: www.nice.org.uk
Last accessed: 03 April 2018
Medscape UK | Univadis prescription drug monographs & interactions are based on FDB Multilex Content
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