These medications prevent the thyroid peroxidase enzymes from producing the thyroid hormones T3 and T4.  The dose given by your doctor depends on the severity of your thyroid condition and the dose will be adjusted during your treatment based on your symptoms and blood test results at each follow-up consultation.  Some patients may need to take the medication for long term so do remember to see your doctor regularly.

Click to view AllHealth TC video on Treating Hyperthyroidism

Minor side effects (can occur in 2-5% of patients)

• Itchiness
• Rashes
• Joint pains
• Fever
• Stomach upset

Major side-effects (can occur in less than 0.3% of patients)

• Anaemia
• Low white blood cell (Agranulocytosis)
• Thrombocytopenia
• Hepatitis (Propylthiouracil)
• SLE like symptoms (Propylthiouracil)
• Cholestatic jaundice (Carbimazole/ Methimazole)

Contraindications

These medications should avoid by patients with

• Serious bone marrow disorder
• Severe liver disease

The most serious potential side effect of the above antithyroid medication is agranulocytosis. This is a condition where the medication interferes and reduce the white blood cell which is the cell that fights infection in our body. Therefore, you must stop the medicine and report this to your doctor immediately if you develop;

• Sore throat
• Mouth ulcers
• High grade fever >38⁰C
• Unexplained bruising or bleeding

Remember to keep your follow-up appointments and do your blood tests regularly to help keep your disease under good control

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If you think you may be suffering from any medical condition, you should seek immediate medical attention from your doctor or other professional healthcare providers. You should never delay seeking medical advice, disregard medical advice, or discontinue medical treatment because of information on this website.