carbimazole at a glance
Medicine class
Thionamide antithyroid treatment.
Main use
Hyperthyroidism, including use around thyroid surgery or radioiodine treatment.
Administration
Swallow tablets whole with water, with or without food.
Monitoring
Thyroid blood tests and safety monitoring are needed before and during treatment.
What is carbimazole used for?
The selected product is licensed for adults and children when reduced thyroid function is required.
Treatment of hyperthyroidism.
Preparation for thyroid surgery in people with hyperthyroidism.
Treatment before and after radioiodine therapy.
How does carbimazole work?
Carbimazole is rapidly converted to thiamazole, also called methimazole. This inhibits steps within the thyroid needed to make thyroid hormones, gradually reducing new hormone production.
carbimazole preparations and strengths
Tablet
Route: Oral
Strengths: 5 mg, 10 mg, 15 mg, 20 mg
How to take carbimazole
Take carbimazole as prescribed. Swallow tablets whole with water, with or without food; taking them with or just after food may help nausea.
Keep appointments for blood tests because treatment is adjusted according to thyroid results.
Tell a pharmacist or prescriber about all medicines, vitamins and supplements, including biotin.
carbimazole side effects
Common or expected effects
- Nausea or mild stomach upset
- Headache or dizziness
- Joint pain
- Itching, mild rash or hives
- Hair thinning or loss
- Altered or lost sense of taste
Get urgent medical advice
- Low white-cell counts or agranulocytosis
- Bone-marrow problems causing unusual bruising or bleeding
- Liver injury
- Acute pancreatitis
- Severe allergy or serious skin reaction
- Muscle pain or weakness, kidney symptoms or nerve pain
carbimazole in pregnancy
Hyperthyroidism requires effective treatment during pregnancy, but carbimazole exposure, particularly early in pregnancy, is associated with a small increased risk of specific birth defects. Anyone planning pregnancy should request a treatment review and use effective contraception until reviewed. If pregnancy occurs, continue treatment initially and contact the prescriber promptly rather than stopping abruptly; specialist assessment and monitoring may be needed.
carbimazole while breastfeeding
carbimazole interactions
Some interactions arise as thyroid function returns towards normal. Medication review and additional monitoring may be required.
Warfarin and other anticoagulants
The anticoagulant effect may change or increase, so clotting tests may need closer monitoring.
Theophylline
Blood concentrations and toxicity risk may increase as hyperthyroidism is treated.
Digoxin and other digitalis glycosides
Blood concentrations can rise as thyroid function normalises.
Common questions about carbimazole
Answers are fully visible for fast scanning and source review.
How quickly does carbimazole work?
It starts affecting hormone production promptly, but symptoms improve gradually as existing thyroid-hormone stores are used.
Why are blood tests needed?
They show whether thyroid function is controlled and help assess suspected blood-cell or liver complications.
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.