Drug reference

Carbimazole

BNF 80 (2020–2021)

Source: BNF 80 (2020–2021)
PDF pages: 836, 837

Review source pages for extracted sections and age labels. BNF dose snippets show only their first line.

Overview

Indications And Dose

Hyperthyroidism ▶BY MOUTH ▶Adult: 15–40 mg daily continue until the patient becomes euthyroid, usually after 4 to 8 weeks, higher doses should be prescribed under specialist supervision only, then reduced to 5–15 mg daily, reduce dose gradually, therapy usually given for 12 to 18 months Hyperthyroidism (blocking-replacement regimen) in combination with levothyroxine ▶BY MOUTH ▶Adult: 40–60 mg daily, therapy usually given for 18 months DOSE EQUIVALENCE AND CONVERSION ▶When substituting, carbimazole 1 mg is considered equivalent to propylthiouracil 10 mg but the dose may need adjusting according to response.

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Contra Indications

Severe blood disorders

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Safety

Important Safety Information

NEUTROPENIA AND AGRANULOCYTOSIS Manufacturer advises of the importance of recognising bone marrow suppression induced by carbimazole and the need to stop treatment promptly. . Patient should be asked to report symptoms and signs suggestive of infection, especially sore throat. . A white blood cell count should be performed if there is any clinical evidence of infection. . Carbimazole should be stopped promptly if there is clinical or laboratory evidence of neutropenia. MHRA/CHM ADVICE: CARBIMAZOLE: INCREASED RISK OF CONGENITAL MALFORMATIONS; STRENGTHENED ADVICE ON CONTRACEPTION (FEBRUARY 2019) Carbimazole is associated with an increased risk of congenital malformations when used during pregnancy, especially in the ﬁrst trimester and at high doses (daily dose of 15 mg or more). Women of childbearing potential should use effective contraception during treatment with carbimazole. It should only be considered in pregnancy after a thorough beneﬁt-risk assessment, and at the lowest effective dose without additional administration of thyroid hormones—close maternal, fetal, and neonatal monitoring is recommended. MHRA/CHM ADVICE: CARBIMAZOLE: RISK OF ACUTE PANCREATITIS (FEBRUARY 2019) Cases of acute pancreatitis have been reported during treatment with carbimazole. It should be stopped immediately and permanently if acute pancreatitis occurs. Carbimazole should not be used in patients with a history of acute pancreatitis associated with previous treatment—re-exposure may result in life-threatening acute pancreatitis with a decreased time to onset.

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Interactions

→Appendix 1: carbimazole

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Side Effects

▶Rare or very rare Bone marrow disorders. haemolytic anaemia. severe cutaneous adverse reactions (SCARs). thrombocytopenia ▶Frequency not known Agranulocytosis. alopecia. angioedema. dyspepsia. eosinophilia. fever. gastrointestinal disorder. generalised lymphadenopathy. haemorrhage. headache. hepatic disorders. insulin autoimmune syndrome. leucopenia. malaise. myopathy. nausea. nerve disorders. neutropenia. pancreatitis acute (discontinue permanently). salivary gland enlargement. skin reactions. taste loss

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Conception And Contraception

The MHRA advises that females of childbearing potential should use effective contraception during treatment.

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Pregnancy

The MHRA advises consider use only after a thorough beneﬁt-risk assessment. See Important Safety Information and Antithyroid drugs p. 814 for further information.

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Breast Feeding

Present in breast milk but this does not preclude breast-feeding as long as neonatal development is closely monitored and the lowest effective dose is used. Amount in milk may be sufﬁcient to affect neonatal thyroid function therefore lowest effective dose should be used.

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Hepatic Impairment

Manufacturer advises use with caution in mild to moderate insufﬁciency—half-life may be prolonged; avoid in severe insufﬁciency.

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Dose and formulations

Medicinal Forms

There can be variation in the licensing of different medicines containing the same drug. Forms available from special-order manufacturers include: capsule, oral suspension, oral solution Tablet ▶Carbimazole (Non-proprietary) Carbimazole 5 mg Carbimazole 5mg tablets | 100 tablet P £84.80 DT = £6.16 Carbimazole 10 mg Carbimazole 10mg tablets | 100 tablet P £104.08 DT = £81.32 Carbimazole 15 mg Carbimazole 15mg tablets | 100 tablet P £156.13 DT = £127.03 Carbimazole 20 mg Carbimazole 20mg tablets | 100 tablet P £208.17 DT = £30.95 ANTITHYROID DRUGS › THIOURACILS

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Clinical care

Patient And Carer Advice

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

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Dose text by age group

Adult

15–40 mg daily continue until the patient

First-line fragment. Read the complete Indications and Dose section above.

PDF page 836

Adult

40–60 mg daily, therapy usually given for

First-line fragment. Read the complete Indications and Dose section above.

PDF page 836

Age labels are extracted for navigation. Check the complete source section and current local guidance before clinical use.

Drug reference

Carbimazole

BNF 80 (2020–2021)

Source: BNF 80 (2020–2021)
PDF pages: 836, 837

Review source pages for extracted sections and age labels. BNF dose snippets show only their first line.

Overview

Indications And Dose

PDF page 836

Contra Indications

Severe blood disorders

PDF page 836

Safety

Important Safety Information

PDF page 836

Interactions

→Appendix 1: carbimazole

PDF page 836

Side Effects

PDF pages 836, 837

Conception And Contraception

The MHRA advises that females of childbearing potential should use effective contraception during treatment.

PDF page 837

Pregnancy

The MHRA advises consider use only after a thorough beneﬁt-risk assessment. See Important Safety Information and Antithyroid drugs p. 814 for further information.

PDF page 837

Breast Feeding

PDF page 837

Hepatic Impairment

Manufacturer advises use with caution in mild to moderate insufﬁciency—half-life may be prolonged; avoid in severe insufﬁciency.

PDF page 837

Dose and formulations

Medicinal Forms

PDF page 837

Clinical care

Patient And Carer Advice

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

PDF page 837

Dose text by age group

Adult

15–40 mg daily continue until the patient

First-line fragment. Read the complete Indications and Dose section above.

PDF page 836

Adult

40–60 mg daily, therapy usually given for

First-line fragment. Read the complete Indications and Dose section above.

PDF page 836

Age labels are extracted for navigation. Check the complete source section and current local guidance before clinical use.