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.lINTERACTIONS→Appendix 1 : carbimazole
lSIDE-EFFECTS
▶Rare or very rareBone marrow disorders.haemolytic
anaemia.severe cutaneous adverse reactions (SCARs).
thrombocytopenia
▶Frequency not knownAgranulocytosis.alopecia.
angioedema.dyspepsia.eosinophilia.fever.
gastrointestinal disorder.generalised lymphadenopathy.
haemorrhage.headache.hepatic disorders.insulin
autoimmune syndrome.leucopenia.malaise.myopathy.
nausea.nerve disorders.neutropenia.salivary gland
enlargement.skin reactions.taste loss
lPREGNANCYCarbimazole can be given but the blocking-
replacement regimen isnotsuitable. Rarely, carbimazole
has been associated with congenital defects, including
aplasia cutis of the neonate. Carbimazole cross the
placenta and in high doses may cause fetal goitre and
hypothyroidism—the lowest dose that will control the
hyperthyroid state should be used (requirements in
Graves’disease tend to fall during pregnancy).
lBREAST FEEDINGPresent 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.
lHEPATIC IMPAIRMENTUse with caution in mild to
moderate impairment. Avoid in severe impairment.
lPATIENT AND CARER ADVICEWarn patient or carers to tell
doctorimmediatelyif sore throat, mouth ulcers, bruising,
fever, malaise, or non-specific illness develops.lMEDICINAL 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 mgCarbimazole 5 mg tablets| 100 tabletP
£ 84. 80 DT = £ 43. 74
Carbimazole 10 mgCarbimazole 10 mg tablets| 100 tabletP
£ 81. 32
Carbimazole 15 mgCarbimazole 15 mg tablets| 100 tabletP
£ 115. 98
Carbimazole 20 mgCarbimazole 20 mg tablets| 100 tabletP
£ 208. 17 DT = £ 144. 47ANTITHYROID DRUGS›THIOURACILS
Propylthiouracil
lINDICATIONS AND DOSE
Hyperthyroidism (including Graves’disease)
▶BY MOUTH
▶Neonate:Initially 2. 5 – 5 mg/kg twice daily until
euthyroid, usually after 8 to 12 weeks, then gradually
reduce to a maintenance dose of 30 – 60 % of the initial
dose; higher initial doses are occasionally required,
particularly in thyrotoxic crisis.▶Child 1–11 months:Initially 2. 5 mg/kg 3 times a day until
euthyroid, usually after 4 to 8 weeks, then gradually
reduce to a maintenance dose of 30 – 60 % of the initialdose; higher initial doses are occasionally required,
particularly in thyrotoxic crisis
▶Child 1–4 years:Initially 25 mg 3 times a day until
euthyroid, usually after^4 to^8 weeks, then gradually
reduce to a maintenance dose of 30 – 60 % of the initial
dose; higher initial doses are occasionally required,
particularly in thyrotoxic crisis
▶Child 5–11 years:Initially 50 mg 3 times a day until
euthyroid, usually after 4 to 8 weeks, then gradually
reduce to a maintenance dose of 30 – 60 % of the initial
dose; higher initial doses are occasionally required,
particularly in thyrotoxic crisis
▶Child 12–17 years:Initially 100 mg 3 times a day until
euthyroid, usually after 4 to 8 weeks, then gradually
reduce to a maintenance dose of 30 – 60 % of the initial
dose; higher initial doses are occasionally required,
particularly in thyrotoxic crisis
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.lUNLICENSED USENot licensed for use in children under
6 years of age.
lINTERACTIONS→Appendix 1 : propylthiouracil
lSIDE-EFFECTS
▶Rare or very rareAgranulocytosis.bone marrow disorders
.glomerulonephritis acute.hearing impairment.
leucopenia.thrombocytopenia.vomiting
▶Frequency not knownAlopecia.arthralgia.arthritis.
encephalopathy.fever.gastrointestinal disorder.
haemorrhage.headache.hepatic disorders.
hypoprothrombinaemia.interstitial pneumonitis.lupus-
like syndrome.lymphadenopathy.myopathy.nausea.
nephritis.skin reactions.taste altered.vasculitis
SIDE-EFFECTS, FURTHER INFORMATIONSevere hepatic
reactions have been reported, including fatal cases and
cases requiring liver transplant—discontinue if significant
liver-enzyme abnormalities develop.
lPREGNANCYPropylthiouracil can be given but the
blocking-replacement regimen isnotsuitable.
Propylthiouracil crosses the placenta and in high doses
may cause fetal goitre and hypothyroidism—the lowest
dose that will control the hyperthyroid state should be
used (requirements in Graves’disease tend to fall during
pregnancy).
lBREAST FEEDINGPresent 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 probably too small to affect infant; high
doses may affect neonatal thyroid function.
MonitoringMonitor infant’s thyroid status.
lHEPATIC IMPAIRMENT
Dose adjustmentsReduce dose.
lRENAL IMPAIRMENT
Dose adjustmentsUse 75 % of normal dose if estimated
glomerularfiltration rate 10 – 50 mL/minute/ 1. 73 m^2.
Use 50 % of normal dose if estimated glomerular
filtration rate less than 10 mL/minute/ 1. 73 m^2.
lMONITORING REQUIREMENTSMonitor for hepatotoxicity.
lPATIENT AND CARER ADVICEPatients should be told how
to recognise signs of liver disorder and advised to seek
prompt medical attention if symptoms such as anorexia,
nausea, vomiting, fatigue, abdominal pain, jaundice, dark
urine, or pruritus develop.484 Thyroid disorders BNFC 2018 – 2019
Endocrine system6