Carbimazole

Please note: these are basic guidelines, refer to your doctor for a professional medical opinion.

Popular brand names:

Neo-Mercazole

Drug group:

Antithyroid drug

Prescription needed?

Yes

What does it do?

Carbimazole is used to manage an overactive thyroid gland (hyperthyroidism).

The most common cause of hyperthyroidism is Graves’ disease:

• 6–18 months of carbimazole can cure Graves’ disease
• It can be used alone or in combination with thyroxine (“block and replace” therapy)
• Carbimazole can be given until treatments such as surgery or radioiodine take effect
• Beta blockers may be given with carbimazole during this period to control symptoms
• It can be given long-term if other treatments are not possible or are declined by the patient

How does it work?

Carbimazole suppresses the formation of thyroid hormone.

How should it be used?

Avoid foods that are high in iodine to help reduce thyroid hormone levels

What is the typical dosage?

Your doctor will recommend a dosage tailored to your need, but typically:

• Initially 15–40mg daily (occasionally a larger dose may be needed), taken 1–3 x daily
• Dosage is reduced gradually to a maintenance dose of 5–15mg for about 18 months

How quickly will it start to work?

Some improvement in symptoms may be noticed within 1–3 weeks, full beneficial effects usually take 4–8 weeks

How long will the effects last?

12–24 hours

When should I stop using it?

Do not stop the drug without consulting your doctor
     

Is it safe for prolonged use?

Long term use of carbimazole can lower your white blood cell count. You may need regular blood tests to monitor thyroid function and white blood cell counts.

What are the possible side effects?

The following have been reported:

• More common: headache, dizziness, joint pain, nausea, reduced sense of taste
• Less common: agranulocytosis (a severe life-threatening reduction in white blood cells)
• Report to your doctor before taking your next dose if you experience: symptoms of agranulocytosis (sore throat/fever/mouth ulcers), jaundice, rash, itching, hair loss

What other considerations are important?

Dosage may be adjusted by your doctor under certain conditions.

• Certain health problems: liver/blood problems
• Other medicines: Theophylline
• Pregnancy and breast-feeding: Risk of foetal abnormalities, but risk to foetus from untreated hyperthyroidism is higher. Breastfeeding requires careful monitoring.
• Children: Reduced dose necessary
• Over 60: No special problems
• Driving and hazardous work: Caution, the drug may cause dizziness
• Alcohol: No known problems