Carbimazole is metabolised to thiamazole which is responsible for its antithyroid action. It blocks the production of thyroid hormones through inhibition of the organification of iodide and the coupling of iodothyronine residues.

Carbimazole is indicated in the management of hyperthyroidism, thyrotoxicosis (including thyroid storm), and also for the preparation of patients for thyroidectomy. Carbimazole can also be used in combination with radio-active ablative therapy

10 mg to 60 mg daily according to the severity of the disorder. The dose should be gradually reduced to the smallest amount which will control the disease. Daily dosage should be divided.

Hypersensitivity to carbimazole or other thiourea antithyroid agents

Nausea, headache, arthralgia, fever, jaundice, malaise, mild gastric distress, skin rashes, pruritus, taste disturbance; bone marrow depression including neutropenia, eosinophilia, leucopenia. Rarely, pancytopenia/aplastic anaemia and isolated thrombocytopenia, haemolytic anaemia.

Overdose Effects

Overdose or accidental poisoning may result in hypothyroidism and goitre. If blood dyscrasias occur, the drug should be immediately withdrawn. Further treatment is symptomatic and supportive.

Caution should be taken in patients with intrathoracic goitre. Mild to moderate hepatic impairment. Caution also should be taken in children, pregnancy and lactation.

Pregnancy & Lactation

Pregnancy Category D. There is positive evidence of human foetal risk, but the benefits from use in pregnant women may be acceptable despite the risk